BIOLOGY Research Today for a Healthier OF Tomorrow AGING NATIONAL INSTITUTE ON AGING NATIONAL INSTITUTES OF HEALTH U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES BIOLOGY OF AGING Research Today for a Healthier Tomorrow AGING UNDER THE METABOLISM The National Institute on Aging MICROSCOPE (NIA), part of the National 23 Does stress really shorten Institutes of Health at the 4 What is aging? your life? U.S. Department of Health and Human Services, was established 6 Living long and well: 27 Does how much you eat to help improve the health and Can we do both? Are affect how long you live? well-being of older people through they the same? IMMUNE SYSTEM research. NIA conducts and 9 Is what’s good for supports research on the medical, mice good for men? 31 Can your immune system social, and behavioral aspects still defend you as you age? of aging. This mission is carried GENETICS out through NIA’s Intramural THE PROMISE OF RESEARCH Research Program composed 13 Is aging in our genes? of staff scientists in Baltimore 35 Past, present, and future and Bethesda, Maryland, and 14 How can we find aging through its Extramural Research genes in humans? 36 GLOSSARY Program, which funds researchers 18 What happens when DNA at major institutions across the 37 BIBLIOGRAPHY United States and internationally. becomes damaged? Biology of Aging: Research Today for a Healthier Tomorrow describes some of NIA’s exciting findings about the basic biology of aging and points to directions for future investigation. BIOLOGY OF AGING: RESEARCH TODAY FOR A HEALTHIER TOMORROW 1 PHOTO CREDIT: MARTY KATZ, WWW.MARTYKATZ.COM 2 AGING UNDER THE MICROSCOPE We marvel at the 90-year-old who still gets up every day and goes to work. And, it is a genuine thrill to celebrate a relative’s 100th birthday. Yet our feelings about aging are complex. We may want to live forever, but who looks about this magical transformation. These forward to getting old? We hope we’re vigor- are the types of questions and kinds of experi- ous right up until the very end. Still, day-to- ences that could stimulate a lifelong quest to day, many of us make unhealthy choices that explore what happens as we age. could put our future at risk. Since the National Institute on Aging (NIA) From the beginning of time, people was established at the National Institutes of have tried to understand aging. Almost Health (NIH) in 1974, scientists asking just every culture has a mythology to explain it. such questions have learned a great deal As we grow up, tales of eternal youth pique about the processes associated with the our curiosity. And, it is these musings that biology of aging. For scientists who study may provide just the spark needed to ignite aging—called gerontologists—this is an excit- a budding scientist. There’s the little girl, ing time. Technology today supports research excited to visit her grandmother, who asks that years ago would have seemed possible her parents how someone so spunky and only in a science fiction novel. And, a scientific fun could be so old. Or, the 3rd grader who, community that values active collaboration as after watching in awe as a caterpillar spins well as individual scientific achievement has a cocoon and then days later emerges as a helped to move research forward faster than butterfly, peppers the teacher with questions ever before. BIOLOGY OF AGING: RESEARCH TODAY FOR A HEALTHIER TOMORROW 3 Over centuries, theories about aging have literally slowed down the runners. Although emerged and faded, but the true nature of the some physical decline may be a normal result aging process is still uncertain. The fact is— of aging, the reasons for these changes are of aging is a part of everyone’s life. But the facts particular interest to gerontologists. of aging—what is happening on a biochemi- Gerontologists look for what distinguishes cal, genetic, and physiological level—remain normal aging from disease, as well as explore rich for exploration. why older adults are increasingly vulnerable This booklet introduces some key areas of to disease and disability. They also try to research into the biology of aging. Each area understand why these health threats take is a part of a larger field of scientific inquiry. a higher toll on older bodies. Since 1958, You can look at each topic individually, or you NIA’s Baltimore Longitudinal Study of Aging can step back to see how they fit together in (BLSA) has been observing and reporting on a lattice-work, interwoven to help us better these kinds of questions. As with any longi- understand aging processes. Research on aging tudinal study, the BLSA repeatedly evaluates is dynamic, constantly evolving based on new people over time rather than comparing discoveries, and so this booklet also keeps an a group of young people to a group of old open eye on the future, as today’s research people, as in a cross-sectional study. Using this provides the strongest hints of things to come. approach, BLSA scientists have observed, for example, that people who have no evidence of ear problems or noise-induced hearing What is aging? loss still lose some of their hearing with In the broadest sense, aging reflects all the age—that’s normal. Using brain scans to learn changes that occur over the course of life. if cognitive changes can be related to struc- You grow. You develop. You reach maturity. tural changes in the brain, BLSA scientists To the young, aging is exciting—it leads to discovered that even people who remain later bedtimes and curfews, and more inde- healthy and maintain good brain function pendence. By middle age, another candle late in life lose a significant amount of brain seems to fill up the top of the birthday cake. volume during normal aging. It’s hard not to notice some harmless cosmetic However, some changes that we have long changes like gray hair and wrinkles. Middle thought of as normal aging can be, in fact, age also is the time when people begin to the signs of a potential disease. Take, for notice a fair amount of physical decline. example, sudden changes in personality. Even the most athletically fit cannot escape A common belief is that people become these changes. Take marathon runners, for cranky, depressed, and withdrawn as they get example. An NIA-funded study found that older. But an analysis of long-term data from their record times increased with age—aging the BLSA showed that an adult’s personality 4 AGING UNDER THE MICROSCOPE POSSIBLE PATHWAYS LEADING TO AGING SIGNALS ENTERING THE CELL CELL NUCLEUS DNA ILLUSTRATION AND INFORMATION ADAPTED FROM WWW.GENOME.GOV FROM ADAPTED INFORMATION AND ILLUSTRATION SIGNALS TO OTHER CELLS To answer questions about why and how we age, some scientists look for mechanisms or pathways in the body that lead to aging. Our cells constantly receive cues from both inside and outside the body, prompted by such things as injury, infection, stress, or even food. To react and adjust to these cues, cells send and receive signals through biological pathways. Some of the most common are involved in metabolism, the regulation of genes, and the transmission of signals. These pathways may also be important to aging. BIOLOGY OF AGING: RESEARCH TODAY FOR A HEALTHIER TOMORROW 5 generally does not change much after age 30. occurs, and what are the biological processes People who are cheerful and assertive when underlying these changes. Scientists look they are younger will likely be the same when deep into our cells and the cells of laboratory they are age 80. The BLSA finding suggests animals to find answers. What they learn today that significant changes in personality are not about aging at the cellular and molecular due to normal aging, but instead may be early levels may, ultimately, lead to new and better signs of disease or dementia. ways to live a longer, healthier life. The rate and progression of cellular aging can vary greatly from person to person. But Living long and well: Can we generally, over time, aging affects the cells of every major organ of the body. Changes can do both? Are they the same? start early. Some impact our health and func- You can hardly turn on your computer these tion more seriously than others. For instance, days without being bombarded with adver- around the age of 20, lung tissue starts to lose tisements that pop up trying to convince you elasticity, and the muscles of the rib cage slowly of the power of a pill that will make you live begin to shrink. As a result, the maximum longer or a cream that will help to revive your amount of air you can inhale decreases. In the youthful vigor and appearance. The search for gut, production of digestive enzymes dimin- ishes, affecting your ability to absorb foods properly and maintain a nutritional balance. Blood vessels in your heart accumulate fatty deposits and lose flexibility to varying degrees, resulting in what used to be called “hardening of the arteries” or atherosclerosis. Over time, women’s vaginal fluid production decreases, and sexual tissues atrophy. In men, aging decreases sperm production, and the prostate can become enlarged. Scientists are increasingly successful at detailing these age-related differences because of studies like the BLSA. Yet studies that observe aging do not identify the reasons for age-related changes, and, therefore, can only go so far toward explaining aging. Questions remain at the most basic level about what triggers aging in our tissues and cells, why it 6 AGING UNDER THE MICROSCOPE ways to stop or reverse the aging process is a FACTORS CONTRIBUTING TO LIFESPAN near-obsession in popular culture.