ERGONOMIC SLEEPING BAG SUPPORT Eliana Palumbo Palumbo 1

Acknowledgements

I would like to thank my parents for their financial support and their patience by putting up with a dining room full of different foams. They were extremely supportive throughout this whole process and were always there to answer any engineering questions I had. I would also like to thank Mr. Regele, Mr. Ellis, Ms. Curran, and Mr. Brunner. I would like to thank them for their guidance throughout the duration of this project because they were always there to brainstorm with me and help me with anything I needed.

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Table of Contents Acknowledgements ...... 1 Abstract ...... 4 Literature Review ...... 5 Insomnia ...... 5 Sleep Debt...... 6 Sleep Deprivation Impairing Emotional Recognition ...... 6 Sleeping Cycles and REM ...... 7 Sleep Number ...... 8 Spinal Alignment ...... 9 Spinal Displacement Side Effects...... 10 Pressure Related Injuries ...... 11 Engineering Plan ...... 14 Engineering Problem Statement ...... 14 Engineering Goals ...... 14 Procedure Overview ...... 14 Methodology ...... 15 Materials ...... 15 Procedure ...... 15 Results ...... 19 Conclusions ...... 20 References ...... 22 Appendix ...... 24 Limitations ...... 24 Assumptions ...... 24 Raw Data ...... 25 Engineering Matrix Ranges ...... 27 Notes File ...... 27 Literature Search Parameters ...... 27 Knowledge Gaps...... 27 DSM-5 Insomnia and Short Sleep ...... 28 Medicated and un-medicated kids with ADHD ...... 29 Sleep Deprivation Impairs Recognition of Specific Emotions ...... 30 Back Alignment ...... 31 Foams...... 32 Palumbo 3

Different Types of Foam ...... 33 Back Alignment 2 ...... 34 Average Lengths of Mattresses and People ...... 35 Sleep Number Mattress ...... 36 Amazon Sleeping Bag Reviews ...... 37 Talking with Ms. Curran ...... 38 Sleep Cycles ...... 39 Sleep Rhythms ...... 40

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Abstract

Sleeping bags do not support the spine properly, maximize sleep time, or optimize sleep quality. A support that is too soft or too hard can cause spinal joint irritation and back pain. If there are unsupported gaps between the body and the support, pressure points may begin to form. Other problems, such as a restriction of blood flow and a constriction of nerves, can arise as a result of a misaligned spine. The purpose of this project was to create an insert for a sleeping bag that would keep the spine in a neutral position, while evenly distributing the sleeper's weight. Five different foams were tested, using a pressure sensor to obtain the contact area, average pressure, and maximum pressure exerted on a model body. A model spine was also developed to assess whether the foams kept the spine in its neutral position. The most effective foam was Memory Foam, as determined by the weight and spine data. Using the foam insert could significantly improve the comfort and support of the sleeping bag user. Palumbo 5

Literature Review

Insomnia

Insomnia is one of the most widespread health concerns and an estimated 30% to 50% of the general population has been affected by insomnia. ("Disorders and Treatments:

Insomnia", 2010) Even though insomnia is so common, clinicians are often reluctant to treat the problem because they have difficulty identifying the cause, they are unfamiliar with some of the treatment options, or have concerns with pharmacologic treatments. This common clinical condition can be distinguished by the difficulty of initiating or maintaining sleep.

Insomnia puts the sleeper at risk for impaired function, and the development of other medical and mental disorders. The causes and observed conditions of insomnia include genetic, environmental, behavioral, and physiological factors that lead up to hyperarousal. After a thorough history of sleep behaviors, medical problems, psychiatric problems, common medications, and a potential record of sleep patterns, insomnia can be diagnosed. If behavioral treatments cannot be used, then medications should be used for the shortest amount of time and in the lowest dosage possible. Clinicians are able to diagnose insomnia because of its effects on function and health; a thorough clinical history is often sufficient to identify factors that contribute to insomnia. Behavioral treatments should be used when possible and hypnotic medications are also efficacious but should be carefully monitored.

(Daniel J. Buysse, 2013)

Insomnia disorder with short sleeping periods is the most severe type of insomnia.

The subjects in a recent study were asked to self-report information like insomnia classification, sleep duration, vascular events, cardiometabolic disease, pain conditions, and psychiatric symptoms. The researchers found that short sleeping insomniacs were at a higher risk of myocardial infarction, stroke, diabetes, chronic pain, back pain, anxiety, and Palumbo 6 depression independent of sex, age, and obesity. Cardiometabolic and psychiatric illness burden was greater for black people with short sleep; black people who experienced sleep disturbances had a greater risk of health problems than their white peers. (Kalmbach, 2016)

Sleep Debt

Sleep debt is known as the difference between the amount of sleep people get and the amount of sleep that their individual body requires. The amount of sleep debt accumulates slowly, and the effects of sleep deprivation vary depending on if the deprivation is short-term or long-term. Short-term effects include worsened vision, a foggy brain, impaired driving, and memory problems, while long-term effects include obesity, heart disease, high blood pressure, strokes, and mood disorders. Because most Americans do not get the sleep their body requires, they suffer from chronic sleep deprivation and experiencing the corresponding side effects. Although experts recommend around 8 hours of sleep while the average

American only sleeps 6.9 hours per night. This sleep deficit can be rectified in a few ways: sleeping an extra 1-2 hours each night over the course of a few months or going to sleep when tired and waking up naturally. Sleep debt cannot be eliminated by simply sleeping two hours longer the next day to offset the two hours missed the night before. As the effects of sleep deprivation dissipate, the body will settle into to a sleep pattern that will improve both physical and mental capabilities. (Webster, 2008)

Sleep Deprivation Impairing Emotional Recognition

One experiment studied the difference in emotional processing after one night of sleep deprivation and one night of recovery sleep. Emotional understanding was determined by an online test that showed the subjects pictures of a man with six different emotional facial cues.

The participants were given the test four times. The participants would see the image, then Palumbo 7 have an unlimited amount of time to click on the emotion label that they thought most accurately represented the face of the man.

The researchers not only identified that session and emotion type significantly influenced the data, but they also identified a significant association between the session and the emotion type. The ability to correctly identify happiness and sadness was reduced after the subjects were sleep deprived, but the ability to recognize the other four emotions (anger, surprise, fear, and disgust) did not show a significant difference. For both happiness and sadness, there was a significant quadratic effect which suggested that sleep deprivation negatively affected the accuracy judgments of the subjects. A quadratic effect means that the first time they took the test and the third time they took the test, they were much better at identifying the emotions, but when they were sleep deprived (second time), they could not identify the emotions nearly as well; the three times they took the test made a quadratic or U shape. The accuracy in the identification of the emotions decreased from the baseline to the sleep deprivation as well as a significant increase from sleep deprivation to recovery. The findings suggest that during times of compromised emotional capacity due to sleep deprivation, the brain may reserve recognition resources that are necessary for responding to threats. These come at the expense of the resources that are available for recognizing less urgent emotions associated with empathy and social relationships. (Killgore, 2017)

Sleeping Cycles and REM

There are two basic types of sleep that are linked to neuronal activity and specific brain waves, these include rapid eye movement (REM) sleep and non-REM sleep. All the stages of non-REM and REM sleep are circled through many times during a usual night.

REM periods grow increasingly longer and deeper towards the morning. Palumbo 8

The first stage of non-REM sleep is the changeover from wakefulness to sleep. This period is several minutes of relatively light sleep where heartbeat, breathing, and eye movements begin to slow, and muscles relax with occasional twitches. Brain waves also begin to slow from their daytime patterns. The second stage of non-REM sleep is a period of light sleep that precedes deeper sleep. Heartbeat and breathing continue to slow, and muscles relax even further while body temperature drops, and eye movements stop. Most of the sleep cycle is taken up by stage 2 sleep than in other sleep stages. The third and final stage of non-

REM sleep is the period of deep sleep that allows the body to feel refreshed the next day.

Heartbeat and breathing begins to slow to their lowest levels during this stage. Muscles are relaxed, and it may become difficult to awaken the sleeping person. REM sleep is the last stage and first occurs about 90 minutes after falling asleep; in this stage, eyes move rapidly from side to side behind closed eyelids. Breathing may become faster and irregular, and heart rate and blood pressure increase to near waking levels. Almost all dreaming occurs during

REM sleep, but some may occur in non-REM sleep. Arm and leg muscles can become temporarily paralyzed, and this will prevent the sleeper from acting out their dreams. As one ages, REM sleep time decreases. ("Brain Basics: Understanding Sleep,” n.d.)

Sleep Number

Mattress companies use this scientific information to ensure the support they are providing, with their mattresses, promote good sleep patterns. Sleep Number beds are one of the most famous mattresses because they have a multitude of options that let the consumers choose every aspect of their product. The Sleep Number Setting allows the users to adjust to their ideal level of firmness and comfort. Responsive Air Technology can sense the users’ movements and then automatically adjusts the firmness and support to keep them sleeping all night long. The FlexFit adjustable base allows the users to raise their partner’s head to alleviate mild snoring. The SleepIQ technology inside the bed is used to track how well the Palumbo 9 user sleeps each night. The Sleep IQ analysis also tells the users their best Sleep Number, best sleep hours, and connects to the users’ favorite health and wellness apps. Their Sleep

Number allows the user to learn how life affects their sleep and how sleep affects their life.

Most customers love their Sleep Number beds, while some are quite displeased. One customer complained that his bed was not firm enough and “even with the sleep number set at 100 [he] still sunk down.” Another customer claimed that “changing settings doesn't exactly help, and it is making [his] back pain worse.” Some customers even made jokes like

“I think the "P" stands for pain in P5” when discussing how back pain seemed to worsen after using the mattress. (“Sleep Number,” Figure 1. An image showcasing the adjustable base n.d.) for the individual settings and a short description of the Sleep IQ. (Sleep Number, n.d.)

Spinal Alignment

When sleeping the body is supposed to heal itself and recover from the day. The muscles and ligaments of the back are supposed to be relaxed and heal themselves while sleeping. A mattress is supposed to allow the sleeper to wake up feeling rested and free of pain or soreness. It should support the natural curve of the spine and provide comfort as well. Simple things can reduce stress on the body and provide targeted support. When sleeping face up, a pillow under the knees and a pillow for under the head will reduce the stress on the spine, by supporting the lower back, neck, and shoulders. When sleeping face down, a pillow under the stomach and pelvis area and either a flat pillow or a pillow under the head can help keep the spine in better alignment. For side sleepers, a pillow between the knees can prevent the upper leg from pulling the spine out of alignment while reducing stress on the hips and lower back. Palumbo 10

A pillow under the head and waist should keep the spine straight and in its neutral position.

While moving during sleep, the entire body should move as one unit, avoiding twisting or turning at the waist to keep the spine and muscles of the back relaxed. (“Good Sleeping

Posture,” n.d.)

A good mattress should conform to the natural curves of the spine. One that is too soft will allow the lower back to sink too far into the mattress, irritate spinal joints and cause lower back pain. A mattress that is too firm will have unsupported gaps between the mattress and the spinal curves. Pressure points, which lead to poor sleep, may begin to develop on the parts of the body in contact with the mattress. If proper posture is maintained, the spine will be aligned and not pinch the spinal cord. A person will appear straighter, taller, and more confident with a strong back that supports their entire body. (“We Know Mattresses,” n.d.)

Figure 2. Comparison of mattresses with different firmnesses, showing the position of the spine on each. (“We Know Mattresses,” n.d.)

Spinal Displacement Side Effects

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Sore Muscles- When slouching, the muscles must work harder to keep the spine stabilized; this can cause tightness and fatigue. Chronic issues may develop from the neck all the way down to the lower back.

Spinal Curvature- The spine has 3 natural curves that make an ‘S’ shape (Figure 3).

Poor posture can lead to increasing pressure which may cause the natural curves to change position. If the natural curve changes, it can compromise the spine’s ability to act as a shock absorber and the person’s ability to stay balanced when standing.

Subluxations- When a vertebra becomes misaligned from the rest of the spine, it affects the overall strength of the spinal column. When the spine is misaligned, it can also lead to chronic stress and irritation of both the spine and its surrounding nerves.

Blood Vessel Constriction- If the spine suffers from subluxations and changes to its curvature, blood vessels can become constricted. Constriction may diminish or cut off blood supply to muscles, impacting oxygen flow to these muscles and other areas.

Nerve Constriction- Poor posture often leads to nerve constriction. As the spine changes shape, the subluxations put pressure on the surrounding spinal nerves. Pinched nerves can cause not only neck and back pain but also pain in other seemingly unrelated areas of the body. (“We Know

Mattresses,” n.d.)

Figure 3. The 3 natural curves of the spine. (“We Know Mattresses,” n.d.) Pressure Related Injuries

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If pressure is reduced on one body part, pressure will increase elsewhere on the body.

The goal any support is to obtain the best pressure redistribution possible, but, all the pressure may never be taken away. Pressure ulcers begin to develop when the capillaries supplying the skin and tissues are compressed enough to impede perfusion; this may ultimately lead to tissue necrosis. The normal blood pressure within capillaries ranges from 20 to 40 mmHg, where 32 mmHg is considered to be the average. Keeping external pressures at less than 32 mmHg should be sufficient for preventing the development of pressure ulcers. Capillary blood pressure may be less than 32 mmHg in ill patient, so, even lower applied pressures may be enough to induce ulceration. Pressure ulcers can develop in as little as 2 to 6 hours.

(Hughes, 2008)

The Braden Scale is designed for adults and consists of 6 subscales: sensory perception, moisture, activity, mobility, nutrition, and friction and shear. It is based on the linking of the clinical situations to the intensity and duration of pressure. The scores on the

Braden Scale range from a 6 (high risk) to 23 (low risk); 18 is the cutoff score for the onset of pressure ulcer risk. (Hughes, 2008)

The buttocks, shoulders, and torso are the heaviest parts of the body, while the head, knees, and feet are lightest. The average person can move as much as 75 times a night, every

6-8 minutes, even during the deepest phase of sleep. To prevent problems from developing from prolonged pressure, such as reduced blood flow, the body will begin to move when sleeping as a protective mechanism. A surface that offers pressure-point relief, by distributing the weight, will reduce tossing and turning throughout the night; if too much pressure is not being exerted, the body will not feel the need to move as frequently. (“Pressure Mapping &

Your Mattress,” 2017) Palumbo 13

During sleep, an ischemia (an inadequate blood supply to an organ or part of the body) may arise. The ischemic event generates metabolic substances that stimulate nerves, which will cause the person to change his or her posture before it becomes painful. When sleeping on a surface that is too firm, the body weight will not be distributed homogenously, and the contact area will be reduced. This reduction in contact area will result in increased pressure and shear forces on the skin and the underlying soft tissues; blood supply may be reduced or even stopped due to the deformation of the tissues. Capillary arteriolar pressure should vary between 3.3 and 4.6 kPa (25 and 35 mmHg), while pressure in the venules approximates to 1.6 kPa (12 mmHg). Critical pressure however, is considered to be around 4 kPa (30 mmHg). The combined effect of time and intensity may result in the development of decubitus ulcers. Most ulcers occur in people who stay in bed for long periods of time, especially when they cannot move themselves or be moved because of an injury (Haex,

2005).

Figure 4. 2D pressure distribution on a

mattress. (“Neurobiology of Sleep,” 2017) Palumbo 14

Engineering Plan

Engineering Problem Statement

Air mattresses and sleeping bags are uncomfortable because they do not support the spine properly, maximize sleep time, or optimize sleep quality.

Engineering Goals

The goal of this project is to create a foam insert for preexisting sleeping bags that will minimize spinal displacement, distribute weight evenly, be cost efficient, and have a quick recovery time.

Procedure Overview

Five different foams were tested to see which was the best when it came to weight distribution. A sheet of foam was placed on a table, followed by the Sensor Edge pressure sensor so that the edges were not tucked under the foam, but were laid out. Then, a Barbie was placed in the center of the sensor, without letting any part of the doll fall over the edge.

Three 2.5 lb. circular weights were put on top of the legs of the Barbie, her chest, and her pelvic area to weight her down. The three weights were positioned so that they were lined up with the center line of the Barbie’s body, so they would not tip over, touch the sensor, or cause an uneven force on the different sides of the doll’s body. A recording of the trial on

Measure X was started immediately after the last weight was put on. After thirty minutes of recording the doll, it would be stopped and saved. The percent contact area, average pressure, and maximum pressure were recorded. The last setting was the table, where the past steps were repeated, except there was no foam placed in-between the table and the sensor. There were 5 trials for the 4 different foams and the table. Palumbo 15

Methodology

Materials

Table 1. The materials used in this project and where they were acquired. Materials From Cost EverFlex V34 Medium-Firm Foam foamorder.com $5.98 EverFlex V44 Firm Foam foamorder.com $5.98 DuraFlex D30 Medium-Firm Foam foamorder.com $3.50 Memory Foam foamorder.com $11.52 Latex Foam Jordan’s n/a Barbell Weights (3) Mass Academy n/a Sensor Edge Pressure Mat Easter Seals n/a Measure X Software on HP Computer Easter Seals n/a ABS Pipe Home Depot $4.52 O Rings Home Depot $4.97 Clear PVC Hose Home Depot $4.78

Procedure

A 12” x 12” x 2” sheet of EverFlex V34 Medium-Firm, EverFlex V44 Firm, DuraFlex

D30 Medium-Firm, Latex Foam and Memory Foam were tested to see which was the best able to distribute weight. First, a foam sheet was placed on a blank table, followed by the

Sensor Edge pressure sensor. The sensor was carefully placed so that the edges were not tucked under the foam. Second, a Barbie was placed in the center of the sensor, without letting any part of the doll fall over the edge. Additionally, three 2.5 lb. circular weights were put flat on top of the doll, where one weight had a slightly larger diameter than the other two.

The weight with the largest diameter was put on top of the legs of the Barbie, where the front edge was lined up with its ankles and the back edge landed on its mid-thigh. The second weight was put on its upper body where the front edge reached its belly button and the back edge landed on its hairline. The last weight was put on top of the other two weights, so the center aligned with the pelvic area. The three weights were positioned so that they were lined up with the center line of the Barbie’s body, so they would not tip over, touch the sensor, or Palumbo 16 cause an uneven force on the different sides of the doll’s body. If when placing the weights on top of the Barbie, one of the weights were to fall off and cause an impression in the foam, everything would be taken off the foam and after three minutes passed, the process would start again. If the placement was successful, a recording of the trial on Measure X was started immediately after the last weight was positioned.

Figure 5. Picture of the Barbie on the foam and sensor with the weights on top of it.

After thirty minutes of recording the doll, the video would be stopped and saved. The weights were left off the foam for five minutes before another test began to give the foam time to recover. To access the data, the “Print” icon was chosen and then a picture (Figure 6.) would be shown displaying the contact area, average pressure, and maximum pressure. This function only shows the data where the curser is in the recording, so the beginning information would be written down, then the video was fast forwarded to the end of the session. That data was recorded using the same method. The last setting was a plain table, where the past steps were repeated, except there was no foam placed in-between the table and the pressure sensor. This was taken to see how the doll’s weight would be distributed with no Palumbo 17 support at all. The number of trials run for the 5 different foams and the table was 5 because of the longer time frame of each trial.

Figure 6. An image of what the “Print” button displayed.

To analyze the data, a two-tailed paired t-test was run to see if there was a difference in the averages of the data before the 30 minutes and after the 30 minutes had passed. A paired t-test was chosen because it can be used to compare two samples in which observations in one can be paired with the observations in the other. An example of a testing comparison includes the 5 data points for the contact area of Foam 1 before the time and the 5 data points for the contact area of Foam 1 after the time frame had passed. This process was repeated for the contact area, average pressure, and the maximum pressure for each foam.

Furthermore, the averages of the before and after for each section were also compared to see how much the averages changed after the time frame passed. Palumbo 18

To test the foam’s recovery time, three circular barbells where placed on top of a sheet of foam. The weights were left there for 5 minutes each and when the 5 minutes ended, the weights were immediately taken off the foam. As soon as they were removed a stopwatch started and when the foam returned to its original neutral position the timer was stopped. If a foam returned to its original position as the weights were removed, then the foam was given a recovery time of 0 seconds.

For spinal displacement testing, a model spine was made. 12, 1-inch long pieces were cut out of PVC pipe that had a diameter of ¾ inch to resemble T2-T13 of the spine. L1-L6 were made from 6, 1 ½ inch long pieces of PVC pipe with a diameter of 1 inch. The 12 pieces were put onto a rubber hose with an outside diameter of ¾ inch. Each piece was separated by a rubber O-Ring with a ¾ inch diameter. The O-Ring was used to provide space in between the spinal pieces and to resemble discs found in the spine. After the 12 were put on then the 6 larger pieces were put on the hose with 2 O-Rings placed in between each.

After all the pieces were on, the ends of the hose were cut off. A copper bar was left inside of the hose overnight, so it would straighten from its curved shape. Refer to Figure 7 to find the final model.

Figure 7. A smaller model spine made of PVC pipes, a hose, and O-Rings.

To test the spinal displacement of the different foams, the model spine and 2 barbell weights were used. First, the desired spinal curve was traced on a large piece of paper. The Palumbo 19 model was then bent to that shape for 30 seconds. The top side of the beginning shape was traced on the sheet of paper. Then, the spine was laid diagonally on the foam so the whole model would be touching it. One weight was then laid on T6 and one on L4. To ensure that the weights would not fall to one side, 4, 1-inch long pieces were cut out of PVC pipe and were used to support the weights on both sides. After the spine was set in place, a timer for

10 minutes was started. When the time was over, the weights were taken off and the spine was traced in a different color on top of its starting curve. This process was repeated five times for each foam. After a test was complete the displacement would then be calculated.

Every inch, the vertical distance from the original curve to the final curve was measured; all the distances were totaled, and that number was the test’s total displacement.

Results

Table 2. Summary data of the contact area, average pressure, and maximum pressure before and after the time interval for each foam. Contact Contact Average Average Maximum Maximum Area Area Pressure Pressure Pressure Pressure Before After Before After Before After (%) (%) (mmHg) (mmHg) (mmHg) (mmHg) Foam 1 4.45 5.49 27.54 30.50 186.05 234.55 Foam 2 4.45 6.07 16.94 20.28 94.32 122.55 Foam 3 2.87 3.38 32.47 37.14 170.95 216.38 Foam 4 3.87 5.31 16.98 18.86 113.56 152.65 Foam 5 5.53 6.35 17.94 23.51 91.22 138.48

The summary data in Table 2. shows the averages of each foam’s subsections. Foam 5 had the highest contact area percentage from 5.53 to 6.35%, while Foam 3 averaged between

2.87 to 3.38%, which was the lowest. Foam 4 had the lowest average pressure ranging from

16.98 mmHg to 18.86 mmHg, opposed to Foam 3 which had the highest that ranged from Palumbo 20

32.47 mmHg to 37.14 mmHg. Foam 2 had the lowest maximum pressure which ranged from

94.32 mmHg to 122.55 mmHg, while 186.05 mmHg to 234.55 mmHg was the highest

belonging to Foam 1. On average, the contact area percentage increased by 1.09% after the

30 minutes. The average pressure also increased by 3.68 mmHg, while the maximum

pressure increased by 41.70 mmHg. When comparing the before and afters of each foam

through a paired t-test, there was a resulting p-value of less than 0.05 for every test.

For the recovery times, Foam 2 had an average time of 12.18 seconds. The 4 other

foams all had an average recovery time of 0 seconds. This meant that when the weights were

removed, the foam instantly went back to its neutral position.

The foam with the lowest spinal displacement was Foam 2 with an average of 1.59

inches. While the foam with the greatest average displacement was Foam 5 at 2.88 inches.

Foam 1 averaged 2.67 inches, Foam 3 averaged 2.20 inches, and Foam 4 averaged 2.80

inches.

Conclusions

Table 3. Engineering Matrix to decipher which was the best foam based on the criteria.

Criteria Maximum Points Foam 1 Foam 2 Foam 3 Foam 4 Foam 5 Low Spinal Displacement 5 2 4 3 2 2 Quick Recovery Time 2 2 1 2 2 2 Low Cost 3 2 1 2 3 2 High Contact Area 5 4 5 1 4 5 Low Average Pressure 5 2 4 1 4 3 Low Maximum Pressure 4 1 4 1 3 4 Total 24 13 19 10 18 18 Percent 100 54 79 42 75 75

Based on the chosen criteria, the best foam would have the highest total percentage

out of the points possible. The foams were given a number for each criterion based on a Palumbo 21 predetermined scale of values that ranked it in comparison to the others. The points were then totaled, and a percentage for each foam was displayed.

Foam 2, which was memory foam, was overall the best out of the 5 because it received the maximum points for contact area, average pressure, and maximum pressure.

Even though it was the most expensive and was the only foam to have a recovery time, it was still the best because of the criteria’s ranking. Foam 4 tied for second place with Foam 5 earning the maximum number of points in recovery time and cost. Foam 5 earned the maximum number of points in recovery time and contact area. Foam 3 had the lowest percentage and only earned the maximum number of points in recovery time.

If this testing were to continue, there are many possible future extensions to this work.

Extensions could include: testing full sheets of foam, making a prototype that will provide support under the insert made from different pipes or foams with different densities, making the insert able to roll up and store easily, and testing competitor’s inserts using the same techniques. When testing the future extensions, using people would be preferable because it would make the quality of the research better. If humans were not able to be used, more advanced anatomical models would be tested.

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References

(n.d.). Retrieved October 13, 2017, from http://www.weknowmattresses.com/2012/02/proper- spinal-alignment/

Brain Basics: Understanding Sleep. (n.d.). Retrieved November 26, 2017, from https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding- Sleep#dreaming Cockcroft, K., Ashwal, J., & Bentley, A. (2009, November). Sleep and daytime sleepiness in methylphenidate medicated and un-medicated children with attention- deficit/hyperactivity disorder (ADHD). Retrieved September 16, 2017, from file:///C:/Users/Eliana/Downloads/49043-65120-1-PB.pdf Daniel J. Buysse. Insomnia. JAMA. 2013;309(7):706–716. doi:10.1001/jama.2013.193 Disorders and Treatments: Insomnia. (n.d.). Retrieved November 20, 2017, from http://www.sleepmanagement.md/sleepdisorders/Insomnia.aspx Good Sleeping Posture Helps Your Back. (n.d.). Retrieved October 5, 2017, from https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=1&Cont entID=4460 Haex, B. (2005). Back and bed: ergonomic aspects of sleeping. Retrieved from https://books.google.com/books?id=CNLAontRAm4C&pg=PA11&lpg=PA11&dq=w eight distribution and pressure when sleeping&source=bl&ots=olCW0ka2V5&sig=Sqei6Y31w5vmM3mTBthcAtbz3lM& hl=en&sa=X&ved=0ahUKEwjqxpKOwOLXAhXBZCYKHed7AhUQ6AEIMzAC#v =onepage&q&f=false Hughes, R. (2008). Patient Safety and Quality: An Evidence-Based Handbook for Nurses. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK2650/ Kalmbach, D. A., Pillai, V., Arnedt, J. T., & Drake, C. L. (2016, December 01). DSM-5 Insomnia and Short Sleep: Comorbidity Landscape and Racial Disparities. Retrieved September 16, 2017, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5103798/#!po=12.2951 Killgore, W. (2017). Neurobiology of Sleep and Circadian Rhythms. (n.d.). Retrieved September 27, 2017, from https://www.journals.elsevier.com/neurobiology-of-sleep- and-circadian-rhythms Palumbo 23

McMaster-Carr. (n.d.). Retrieved October 7, 2017, from https://www.mcmaster.com/#standard-foam-sheets/=19r1gng

Pressure Mapping & Your Mattress. (2017, October 16). Retrieved November 12, 2017, from http://restonic.com/blog/pressure-mapping-and-your-mattress-1975

Rest 'N' Roll Easy Store Single Camping Sleeping Pad with Carrying Straps. (n.d.). Retrieved October 17, 2017, from https://www.amazon.com/Single-Camping-Sleeping- Carrying-Straps/product- reviews/B00EMJVPIQ/ref=cm_cr_dp_d_hist_1?ie=UTF8&filterByStar=one_star&re viewerType=all_reviews-filter-bar

Sleep Number Site | Adjustable Beds, Memory Foam Mattresses, Kids Beds, Pillows & More. (n.d.). Retrieved October 17, 2017, from https://www.sleepnumber.com/

Types of Foam - An In-Depth Look at Different Foam Mattresses. (2017, September 30). Retrieved October 15, 2017, from https://www.thesleepjudge.com/types-of-foam/

Webster, M. (2008, May 6). Can You Catch Up on Lost Sleep? Retrieved August 28, 2017, from https://www.scientificamerican.com/article/fact-or-fiction-can-you-catch-up-on- sleep/

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Appendix

Limitations

1. Weight Distribution tests took 30 minutes each so the number of times the test could

be run was limited to 5 per foam.

2. Human testing was not allowed, so dolls and models had to be used to simulate

human bodies.

3. Funding was limited so only a few foams could be bought.

Assumptions

1. Complications like subluxations and the formation of pressure points arise because of

the support the body is lying on and not the body itself.

2. Smaller models of the human body are representative of larger bodies.

3. A Barbie has a similar enough body shape to a human, to be used to simulate a human

lying on foam.

4. A model spine is representative of a human spine when laid on top of the foam.

5. The Sensor Edge gave accurate readings pertaining to the contact area, average

pressure, and maximum pressure of the doll.

6. The foams received from foamorder.com were the foams that were advertised and

ordered online.

7. A model spine made from ABS piping, O-Rings, and Clear PVC piping resemble the

way a human spine moves.

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Raw Data

Table 4. Raw weight distribution data. Foam 1 Foam 2 Before After Before After Contact Area (%) 4.20 5.86 Contact Area (%) 2.93 5.18 4.30 5.27 4.20 5.27 4.39 5.76 4.69 6.54 4.49 4.79 4.96 6.54 4.88 5.76 Diff 5.47 6.84 Diff Average 4.45 5.49 1.04 Average 4.45 6.07 1.62

Before After Before After Average Pressure 18.01 22.96 Average Pressure 14.48 16.75 (mmHg) 27.03 31.31 (mmHg) 15.96 18.48 27.25 31.07 16.77 18.74 30.60 32.00 18.36 25.47 34.83 35.15 Diff 19.14 21.96 Diff Average 27.54 30.50 2.95 Average 16.94 20.28 3.34

Before After Before After Maximum Pressure 86.36 124.10 Maximum Pressure 68.77 87.39 (mmHg) 143.75 206.32 (mmHg) 87.39 108.59 176.33 207.87 99.8 156.16 250.79 314.91 106.52 127.21 273.03 319.57 Diff 109.11 133.41 Diff Average 186.05 234.55 48.50 Average 94.318 122.55 28.23

Foam 3 Foam 4 Before After Before After Contact Area (%) 2.64 3.13 Contact Area (%) 2.73 4.69 2.73 3.52 2.83 4.88 2.73 3.22 3.91 5.57 3.03 3.52 4.88 5.57 3.22 3.52 Diff 4.98 5.86 Diff Average 2.87 3.38 0.51 Average 3.87 5.31 1.45

Before After Before After Average Pressure 24.75 29.62 Average Pressure 15.06 18.31 (mmHg) 27.82 34.59 (mmHg) 15.31 17.70 32.85 37.39 15.37 18.53 38.01 43.15 19.03 18.51 38.93 40.97 Diff 20.13 21.27 Diff Average 32.47 37.14 4.67 Average 16.98 18.86 1.88 Palumbo 26

Before After Before After Maximum Pressure 85.32 117.90 Maximum Pressure 64.64 86.87 (mmHg) 155.13 197.02 (mmHg) 89.98 143.75 158.75 217.18 97.21 130.83 207.36 250.79 117.90 178.40 248.21 298.99 Diff 198.05 223.39 Diff Average 170.95 216.38 45.42 Average 113.56 152.65 39.09

Foam 5 Before After Contact Area (%) 3.81 4.30 5.66 6.93 5.76 6.93 6.15 6.84 6.25 6.74 Diff Average 5.53 6.35 0.82

Before After Average Pressure 16.70 21.41 (mmHg) 16.73 22.16 17.58 24.56 19.06 25.60 19.65 23.83 Diff Average 17.94 23.51 5.57

Before After Maximum Pressure 69.29 113.76 (mmHg) 81.18 116.86 96.18 123.07 103.94 197.02 105.49 141.69 Diff Average 91.22 138.48 47.26

Table 5. Raw spinal displacement data.

Spinal Displacement Data (in) Foam 1 Foam 2 Foam 3 Foam 4 Foam 5 2.625 2.125 2.500 2.438 3.063 4.438 1.063 2.063 2.063 2.500 1.688 1.625 2.188 3.500 2.438 1.938 1.563 2.063 3.188 3.500 Average 2.672 1.594 2.203 2.797 2.875 Palumbo 27

Engineering Matrix Ranges

Table 6. A display of the ranges that were used to score the different foams in the engineering matrix. Maximum Criteria 5 Points 4 Points 3 Points 2 Points 1 Point Points Spinal 5 0-1.5 inches 1.5-2 inches 2-2.5 inches 2.5-3 inches 3 inches+ Displacement Recovery 10 2 n/a n/a n/a 0-10 seconds Time seconds + Cost 3 n/a n/a 0-5$ 5-10$ 10$ +

Contact Area 5 5 % + 4.5-5% 4-4.5% 3.5-4% 0-3.5% Average 30 5 0-15 mmHg 15-20 mmHg 20-25 mmHg 25-30 mmHg Pressure mmHg + Maximum 120-150 150-180 180 4 n/a 0-120 mmHg Pressure mmHg mmHg mmHg +

Notes File

Literature Search Parameters Database/ Search Engine Keywords

WPI Summon Sleep, insomnia WPI Summon Medicated sleep WPI Summon Sleep deprivation Google Sleeping posture Google Mattress foams Google Spine alignment, sleep Google Bed lengths Google Amazon, sleeping bag WPI Summon Average height Google Sleep Number

Knowledge Gaps Knowledge Gap Resolved by Information is Located

How does artificial light affect Reading Sleep Abstract Doc Notes

sleeping habits?

What foams will be the best Reading Foams material? Palumbo 28

How will I decipher between Talking with Mrs. Curran Logbook the foams? How will I see the position of Talking with Curran/ Talking with Mr. Brunner, Mr. the spine? brothers doctor? Ellis, and Mr. Regele

Source DSM-5 Insomnia and Short Sleep Title Source Kalmbach, D. A., Pillai, V., Arnedt, J. T., & Drake, C. L. (2016, December 01). DSM- Citation 5 Insomnia and Short Sleep: Comorbidity Landscape and Racial Disparities. Retrieved September 16, 2017, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5103798/#!po=12.2951 Source Searched “insomnia” in the US National Library of Medicine found by Source Journal Article Type Keywords DSM-5, insomnia, racial disparities, comorbidity Summary -examined the roles of insomnia and short sleep in racial disparities in disease burden black and white Americans Reason Wanted to learn about insomnia cause/effect for Interest Notes -insomnia disorder with short sleep is the most severe phenotype of insomnia -subjects self-reported insomnia classification, sleep duration, vascular events, cardiometabolic disease, pain conditions and psychiatric symptoms -short sleeping insomniacs were at a higher risk for myocardial infarction, stroke, diabetes, chronic pain, back pain, anxiety, and depression independent of sex, age, and obesity -cardiometabolic and psychiatric illness burden was greater for blacks with short sleep -blacks with sleep disturbances have a greater risk of health problems than whites Questions Why are black people more susceptible to health problems than white people?

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Source Medicated and un-medicated kids with ADHD Title Source Cockcroft, K., Ashwal, J., & Bentley, A. (2009, November). Sleep and daytime Citation sleepiness in methylphenidate medicated and un-medicated children with attention- deficit/hyperactivity disorder (ADHD). Retrieved September 16, 2017, from file:///C:/Users/Eliana/Downloads/49043-65120-1-PB.pdf Source Searching “medicated sleep” in WPI library for journal articles found by Source Journal Article Type Keywords methylphenidate, ADHD, daytime sleepiness Summary Study which compared the perceived levels of daytime sleepiness and prevalence of sleep disorders in medicated and un-medicated children with ADHD. Reason Wanted to study differences between medicated and un-medicated sleep for Interest Notes -two groups: one taking methylphenidate twice daily and the other taking no meds -the kids and their parents both rated their levels of sleepiness at three points in the day -significantly higher levels of daytime sleepiness was reported for the un-medicated group around 1 to 3 o’clock compared to the medicated group -there was a significant increase in sleepiness a few hours after taking the medicine which could have an impact on their learning -the medication had a significant effect because it reduced the level of sleepiness for the duration of the action of it Questions n/a

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Source Sleep Deprivation Impairs Recognition of Specific Emotions Title Source Neurobiology of Sleep and Circadian Citation Rhythms. (n.d.). Retrieved September 27, 2017, from https://www.journals.elsevier.com/neurobio logy-of-sleep-and-circadian-rhythms Source Searching in WPI Summon. found by Source Journal Article Type Keywords Deprivation, recognition, emotions Summary -studied the difference in emotional processing after one night of sleep deprivation and one night of recovery sleep. The difference in responses for the emotional detections was determine d by an online test that showed the subjects pictures of a man with different facial cues. The researchers found that, although both genders were equally accurate following sleep deprivation, subjects of different genders recognized different emotions. The ability to correctly identify happiness and sadness was reduced after the subjects were sleep deprived but the ability to recognize the other four emotions (anger, surprise, fear, and disgust) did not show a significant difference. Reason How does sleep deprivation affect the brain? for Interest Notes After sleep, wakefulness Subjects underwent 8 and the rest day, they were hours of sleep, 61 hours of tested to see if there was a wakefullness and finally 12 difference in how sleep hours of sleep. deprivation affected emotional recognition.

The test consisted of The label order was morphed expression randomized and the photos of 2 of the 6 picture was shown for 5 emotions and tested the seconds. These were done subjects ability to to try to reduce the recognize different variablity and minimize emotions. bias.

The data was then analyzed by the sex of the subject, the test session, their reaction time, and the emotion category.

Questions n/a

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Source Back Alignment Title Source Good Sleeping Posture Helps Your Back. (n.d.). Retrieved October 5, 2017, from Citation https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=1&Content ID=4460 Source Google Search found by Source Website Type Keywords sleeping, posture Summary -keep your ears, shoulders, and hips aligned - either pillows or the mattress itself should fill the gaps between your body and the mattress

Reason How should the back be positioned? for Interest Notes -muscles and ligaments of your back relax and heal themselves while you sleep -mattress that's right for you lets you wake up feeling rested and free of pain or soreness -choose a mattress that provides support for the natural curves of your spine and is comfortable -sleeping on your back: a small pillow under your knees-> reduce stress on your spine and support the natural curve in your lower back, pillow for your head should support the natural curve of your neck, and your shoulders -sleeping on your stomach: a pillow under the stomach and pelvis area can help to keep the spine in better alignment, a pillow for your head should be flat, or sleep without one -sleeping on your side, a pillow between your knees will prevent the upper leg from pulling the spine out of alignment and reduce stress on the hips and lower back, pull knees up slightly toward the chest, pillow for your head should keep your spine straight, pillow under your waist too -do not twist or bend at the waist, move your entire body as one unit, keep your belly pulled in and tightened, and bend your knees toward the chest when you roll

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Source Foams Title Source McMaster-Carr. (n.d.). Retrieved October 7, 2017, from Citation https://www.mcmaster.com/#standard-foam-sheets/=19r1gng Source Suggested by Mrs. Curran found by Source Website Type Keywords Density, texture, resiliency, specifications Summary A website that allows me to put in a specific type of foam and it tells me: prices, material, shape, thickness, size, colors, and the pressure to compress the foam, temp range, etc. It gives a short summary of the foam, talking about the compression recovery time, cell construction and environmental limitations. Reason Where can I find the foams properties? for Interest Notes

Questions n/a

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Source Different Types of Foam Title Source Types of Foam - An In-Depth Look at Different Foam Mattresses. (2017, September Citation 30). Retrieved October 15, 2017, from https://www.thesleepjudge.com/types-of-foam/ Source Google Search found by Source Website Type Keywords Polyurethane, memory foam, gel, Evlon Summary For each type of foam, it mentions common places you can find it, what it is, common customer complaints, broad pricing, temperature regulation, etc. Reason Which foams will I test? for Interest Notes Consequences of not getting enough sleep include: obesity, hypertension, diabetes, mood disorders, heart disease, and shortened life expectancy Different Types of Foams: Polyurethane Foam, Traditional Memory Foam, Open Cell Memory Foam, Gel Memory Foam, Gel Foam, Reflex Foam, Convoluted Foam and Evlon Questions n/a

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Source Back Alignment 2 Title Source (n.d.). Retrieved October 13, 2017, from Citation http://www.weknowmattresses.com/2012/02/proper-spinal-alignment/ Source Google Search found by Source Website Type Keywords Spinal alignment, nervous system, posture Summary Proper spinal alignment: a good mattress will conform to the spines natural curves and keep your spine in proper alignment, a mattress that is too soft allows the lower back to sink too far into the mattress, irritating spinal joints and causing lower back pain, a mattress that is too firm leads to unsupported gaps between your bodies curves and the mattress., pressure points develop on those parts of your body in contact with the mattress- leading to poor sleep Reason What is the proper posture for sleeping? What can happen if posture is bad? for Interest Notes -spend 1/3 of your life in bed -proper posture: spine is aligned, not pinching spinal cord, appear straight, taller, and confident and the back is strong and supports the rest of the body properly. - Side effects of poor spinal alignment include: Sore Muscles– If you slouch, your muscles must work harder to keep your spine stabilized, which can cause tightness and fatigue. Chronic issues may develop from your neck all the way to your lower back. Spinal Curvature– Your spine has 3 natural curves that make and ‘S’ shape (4 if you include the non-moving curve at the base of the spine). Poor posture can lead to pressure, influencing those curves to change position. If the natural curve changes, it compromises the spines ability to act as a shock absorber and for you to keep your balance. Subluxations– when a vertebra becomes misaligned from the rest of the spine, which affects the overall strength of your spinal column. This can also lead to chronic stress and irritation of the spinal column and surrounding nerves. Blood Vessel Constriction– If your spine begins to suffer from Subluxations and changes to its curvature, your blood vessels can become constricted- diminishing or cutting off blood supply to muscles, which impacts oxygen flow to these muscles and other areas. Nerve Constriction– Bad posture often leads to nerve constriction. Subluxations put pressure on the surrounding spinal nerves. Pinched nerves cause not only neck and back pain, but also pain in other seemingly unrelated areas of your body. Questions n/a

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Source Average Lengths of Mattresses and People Title Source -National Center for Health Statistics. (2017, May 03). Retrieved October 3, 2017, from Citation https://www.cdc.gov/nchs/fastats/body-measurements.htm -Mattress Size Chart. (n.d.). Retrieved October 3, 2017, from http://www.sleeptrain.com/mattress-size-chart/education-mattress-size-chart.html Source Google Search found by Source Website Type Keywords National, height, Summary Twin beds are normally 39 inches by 74 inches and US male average height is 69.2 inches while the female average height is 63.7 inches. Reason How long should I make the mattress/insert? for Interest Notes

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Source Sleep Number Mattress Title Source Sleep Number Site | Adjustable Beds, Memory Foam Mattresses, Kids Beds, Pillows Citation & More. (n.d.). Retrieved October 17, 2017, from https://www.sleepnumber.com/ Source Google Search found by Source Website Type Keywords SleepNumber, SleepIQ Summary SleepNumber: lets you adjust your idea of comfort->firmness SleepIQ: The Sleep Number bed with SleepIQ technology inside tracks how well you sleep each night, giving you personal insights into your sleep. Tells you your best SleepNumber, best sleep hours for you and it even connects to your favorite health and wellness apps, so you'll learn how life affects your sleep and how sleep affects your life. Reason for What makes this such a good bed? Why the high price tag? Interest Notes For kid’s beds: parent can track the quality and quantity of the child’s sleep and turn lights off remotely. They also have a head-tilt option and soft under bed lighting that turns on when the child gets up at night.

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Source Amazon Sleeping Bag Reviews Title Source Rest 'N' Roll Easy Store Single Camping Sleeping Pad with Carrying Straps. (n.d.). Citation Retrieved October 17, 2017, from https://www.amazon.com/Single-Camping-Sleeping- Carrying-Straps/product- reviews/B00EMJVPIQ/ref=cm_cr_dp_d_hist_1?ie=UTF8&filterByStar=one_star&revi ewerType= all_reviews-filter-bar Source Google Search found by Source Website Type Keywords Sleeping bag, reviews, cheap Summary This pad was made to go inside or under a sleeping bag so provide support. Many customers did not like it and said that it was cheap and did not provide comfort.

Reason for What is wrong with sleeping bags/ pads today? Interest Notes “Thinner than a yoga mat,” “sleeping on a paper towel will be just as good,” “it's very thin and lightweight, used it one time ripped that same day...it is a very lightweight Styrofoam mat,” “you will feel every rock beneath you, assuming it doesn't disintegrate after an hour of use,” and “No cushion or insulation from cold at all. Might work as a cheap yoga mat or ground cover if you are going to the beach or park but not for camping.” Questions n/a

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Source Talking with Ms. Curran Title Source 10/25/17 Citation Source Talking found by Source Speech Type Keywords Sleeping pad, pressure sensors, clay, weights Summary Talk to people. Reason for InterestHad some questions about how I will get data.

Notes -observe how and how much it compresses -will it compress over time? -video tape it with either the -visit Easter Steals on Main Street in Worcester, mat with numerical and heat labels that changes colors -are there places that everyone will need extra support even though people are different sizes? -will it be adjustable? -make a possible “person” out of clay, wires, and weights to stimulate a real person and spine sleeping on the pad -reach out to the sleep clinic and ask questions about the project and spinal positions -test the different stresses and compression properties -some sort of website that shows the normal proportions of the body (med or art websites?) ask Mr. Brunner?? ->histogram of the average qualities (human factors and anthropometrics) -ask previous senior about the drop tests with pressure sensors -make a list of things that I want it to do, what are some deal breakers if I was a customer going to use it? Questions n/a

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Source Sleep Cycles Title Source Brain Basics: Understanding Sleep. (n.d.). Retrieved November 26, 2017, from Citation https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding- Sleep#dreaming Source Searching REM Sleep into google. found by Source Website Type Keywords REM, tips Summary There are four different stages of sleeping that are broken up into two types (non-REM sleep and REM sleep). There are also some simple things that you can do to increase the chance of having a good night’s sleep. Reason Need more background on sleep itself for Interest Notes Tips for good nights sleep: Set a schedule – go to bed and wake up at the same time each day. Exercise 20 to 30 minutes a day but no later than a few hours before going to bed. Avoid caffeine and nicotine late in the day and alcoholic drinks before bed. Relax before bed – try a warm bath, reading, or another relaxing routine. Create a room for sleep – avoid bright lights and loud sounds, keep the room at a comfortable temperature, and don’t watch TV or have a computer in your bedroom. Don’t lie in bed awake. If you can’t get to sleep, do something else, like reading or listening to music, until you feel tired.

Sleep Stages: Stage 1 non-REM sleep is the changeover from wakefulness to sleep. During this short period (lasting several minutes) of relatively light sleep, your heartbeat, breathing, and eye movements slow, and your muscles relax with occasional twitches. Your brain waves begin to slow from their daytime wakefulness patterns. Stage 2 non-REM sleep is a period of light sleep before you enter deeper sleep. Your heartbeat and breathing slow, and muscles relax even further. Your body temperature drops, and eye movements stop. Brain wave activity slows but is marked by brief bursts of electrical activity. You spend more of your repeated sleep cycles in stage 2 sleep than in other sleep stages. Stage 3 non-REM sleep is the period of deep sleep that you need to feel refreshed in the morning. It occurs in longer periods during the first half of the night. Your heartbeat and breathing slow to their lowest levels during sleep. Your muscles are relaxed, and it may be difficult to awaken you. Brain waves become even slower. REM sleep first occurs about 90 minutes after falling asleep. Your eyes move rapidly from side to side behind closed eyelids. Mixed frequency brain wave activity becomes closer to that seen in wakefulness. Your breathing becomes faster and irregular, and your heart rate and blood pressure increase to near waking levels. Most of your dreaming occurs during REM sleep, although some can also occur in non-REM sleep. Your arm and leg muscles become temporarily paralyzed, which prevents you from acting out your dreams. As you age, you sleep less of your time in REM sleep. Memory consolidation most likely requires both non-REM and REM sleep. Questions n/a

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Source Sleep Rhythms Title Source Brain Basics: Understanding Sleep. (n.d.). Retrieved November 26, 2017, from Citation https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding- Sleep#dreaming Source Searching REM Sleep into google. found by Source Website Type Keywords Homeostasis, circadian rhythms Reason Learning more about sleep patterns and rhythms for Interest Notes Circadian rhythms direct a wide variety of functions from daily fluctuations in wakefulness to body temperature, metabolism, and the release of hormones. They control your timing of sleep and cause you to be sleepy at night and your tendency to wake in the morning without an alarm. Your body’s biological clock, which is based on a roughly 24-hour day, controls most circadian rhythms. Circadian rhythms synchronize with environmental cues (light, temperature) about the actual time of day, but they continue even in the absence of cues.

Sleep-wake homeostasis keeps track of your need for sleep. The homeostatic sleep drive reminds the body to sleep after a certain time and regulates sleep intensity. This sleep drive gets stronger every hour you are awake and causes you to sleep longer and more deeply after a period of sleep deprivation. Factors that influence your sleep-wake needs include medical conditions, medications, stress, sleep environment, and what you eat and drink. Perhaps the greatest influence is the exposure to light. Specialized cells in the retinas of your eyes process light and tell the brain whether it is day or night and can advance or delay our sleep-wake cycle. Exposure to light can make it difficult to fall asleep and return to sleep when awakened. Night shift workers often have trouble falling asleep when they go to bed, and have trouble staying awake at work because their natural circadian rhythm and sleep-wake cycle is disrupted. In the case of jet lag, circadian rhythms become out of sync with the time of day when people fly to a different time zone, creating a mismatch between their internal clock and the actual clock. Questions n/a