AMBIENT LIGHT AND SLEEP IN COMMUNITY DWELLING OLDER ADULTS By ASHLEY MAE STRIPLING A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2008 1 © 2008 Ashley Mae Stripling 2 To all who light up life 3 ACKNOWLEDGMENTS I would like to thank my chair Dr. Christina McCrae for her intellectual guidance and constant mentoring; my supervisory committee members for their time and recommendations; the Sleep Research Lab for their support, Amanda Ross, Natalie Dautovich, Joseph MacNamara, and Joseph Dzierzewski; my parents, Richard and Rozann Stripling for their unconditional love and unvarying support through my entire educational process; and Rome Cagnina for editing countless copies of this work. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................................... 4 LIST OF TABLES................................................................................................................................ 7 LIST OF FIGURES .............................................................................................................................. 8 ABSTRACT .......................................................................................................................................... 9 INTRODUCTION .............................................................................................................................. 11 REVIEW OF THE LITERATURE ................................................................................................... 13 Ambient Light ............................................................................................................................. 14 Biological Underpinnings of the Ambient Light-Sleep Relationship ...................................... 15 Empirical Support in Animals ............................................................................................ 15 Empirical Support in Humans ............................................................................................. 16 Empirical Support in Older Adults ..................................................................................... 18 Naturalistic Studies of Ambient Light and Sleep in Older Adults ................................... 19 Sleep Measurement ..................................................................................................................... 22 Objective (Actigraphy) Measurement of Sleep ................................................................. 22 Subjective Measurement in the Study of Sleep ................................................................. 24 Factors Influencing the Older Adult Ambient Light/Sleep Relationship ................................ 26 Endogenous Factors ............................................................................................................. 26 Physical Health .................................................................................................................... 27 Mental Health....................................................................................................................... 28 Exogenous Factors ............................................................................................................... 29 Summary of the Innovations of the Present Study .................................................................... 30 PURPOSE AND HYPOTHESES...................................................................................................... 34 Specific Aim 1: to Explore the Relationships between Age, Health, Daytime Functioning, Ambient Light, and Sleep (Objective and Subjective). .................................. 34 Hypothesis 1-Relationships between the Age, Health, Daytime Functioning, Ambient Light, and the Sleep Variables: ....................................................................... 34 Specific Aim 2: to Examine the Amount of Variance in Sleep Accounted for by Ambient Light.......................................................................................................................... 34 Hypothesis 2 ......................................................................................................................... 34 Specific aim 3: What Are the Incremental Contributions of Age, Health, Daytime Functioning, and Ambient Light (in that Order) to the Prediction of Sleep? ...................... 35 Hypothesis 3 ......................................................................................................................... 35 METHODS ......................................................................................................................................... 36 Participants and Procedure ......................................................................................................... 36 5 Measures ...................................................................................................................................... 37 Objective Sleep .................................................................................................................... 37 Subjective Sleep ................................................................................................................... 39 Ambient Light ...................................................................................................................... 39 Health and Daytime Functioning ............................................................................................... 40 Demographics and Health Survey ...................................................................................... 40 Beck Depression Inventory-Second Edition ...................................................................... 40 Stait-Trait Anxiety Inventory – Form Y1 .......................................................................... 40 Fatigue Severity Scale ......................................................................................................... 41 Statistical Analysis ...................................................................................................................... 41 RESULTS............................................................................................................................................ 43 Specific Aim 1: to Explore the Relationships between Age, Health, Daytime Functioning, Ambient Light, and Sleep (Objective and Subjective). .................................. 43 Specific Aim 2: to Examine the Amount of Variance in Sleep Accounted for by Ambient Light.......................................................................................................................... 43 Linear Regressions............................................................................................................... 43 Specific aim 3: What Are the Incremental Contributions of Age, Health, Daytime Functioning, and Ambient Light (in that Order) to the Prediction of Sleep? ...................... 44 Hierarchical Block Regressions .......................................................................................... 44 DISCUSSION ..................................................................................................................................... 48 Review of Study Findings .......................................................................................................... 48 Specific Aim 1: to Explore the Relationships between Age, Health, Daytime Functioning, Ambient Light, and Sleep (Objective and Subjective). .................................. 48 Specific Aim 2: to Examine the Amount of Variance in Sleep Accounted for by Ambient Light.......................................................................................................................... 50 Specific aim 3: What Are the Incremental Contributions of Age, Health, Daytime Functioning, and Ambient Light (in that Order) to the Prediction of Sleep? ...................... 51 Limitations of the Study ............................................................................................................. 52 Implications and Future Directions ............................................................................................ 52 Conclusion ................................................................................................................................... 53 LIST OF REFERENCES ................................................................................................................... 54 BIOGRAPHICAL SKETCH ............................................................................................................. 64 6 LIST OF TABLES Table page 4-1 Sample Characteristics ........................................................................................................... 42 5-1 Pearson Correlations between Subjective (Sleep Diary), Objective (Actigraphy) Sleep Variables, and Age, Health, Daytime Functioning Variables, and Ambient Light ........................................................................................................................................ 46 5-2 Summary of Hierarchical Regression Analysis for Variables Predicting Subjective Total Wake Time .................................................................................................................... 47 7 LIST OF FIGURES Figure page 2-1 Visual representation of Mesor, Acrophase and