Written by Quynh Teresa H. Do and Edited by Myra Ali
Ever since the 20th century, the mortality rate in the United States has declined immensely. According to the University of Southern California, Leonard Davis School of Gerontology, people are now able to to live almost twice as long due to the new advancements in medicine, healthcare services, and healthcare coverage programs [1]. Human longevity has been increasing constantly with such developments; however, there is a lack of studies on the oldest-old of the world. The question stands: how do the oldest of the old, such as centenarians and even supercentenarians, live to as long as they do?
Dr. Claudia Kawas and Dr. Maria Corrada from the University of California, Irvine have been researching these individuals for over 15 years. One of their studies, the 90+ study, was initiated in 2003 at the UCI Institute for Memory Impairments and Neurological Disorders to better understand how these individuals above the age of 90 live for so long. These researchers have examined different aspects of the participants’ lives such as sleep, diet, exercise, and activities. The current research objective of this study is to determine which factors are associated with longevity and examine how the population develops dementia, cognitive/functional decline, and certain pathologies [2].
However, perhaps the largest goal of this study is to understand the presence of Alzheimer’s disease (AD) and dementia in the oldest of the old. Dementia is an umbrella term for symptoms dealing with memory loss while AD is a cause of dementia, specifically progressive dementia. Age is the number one risk factor for developing AD, yet there are many older individuals who do not develop the disease. One of the many studies in regards to understanding AD and dementia within the 90+ Study is on sleep, hippocampal volume, and cognition in adults over 90 years old. This study aims to find any relations between the quality/quantity of sleep reported by the participants and hippocampal volume and cognition. The hippocampus is a structure in the brain that is important for memory and knowledge acquisition. A larger hippocampus volume is indicative of higher cognitive abilities, which includes acquiring knowledge and processing thoughts, experiences, and senses [3]. For this study, 144 participants filled out a questionnaire on their sleep activity and were then tested on their cognitive abilities using the Mini-Mental State Examination (MMSE), the California Verbal Learning Test (CVLT), and the Boston Naming Test (BNT). Their executive function was also tested through use of the Trail Making Test B (TMT B). The MMSE has 15 questions scored on a 0–30 scale to measure cognitive impairment in older adults. The CVLT tests memory using free recall of a list of nine words and the BNT tests word retrieval using 15 items. The TMT B is a test that asks participants to connect letters and numbers in the correct order and measures the time taken to complete the task. High scores on all of these tests indicate better cognition. 3 Tesla Magnetic Resonance Imaging (3 T MRI) was used to visualize the hippocampus in 82 participants. MRI is a brain imaging technique that uses magnetic fields and waves. Using 3 T MRI, an image of the brain can be generated and this can be used to detect structural abnormalities of the brain such as inflammation and shrinkages. Through this study, the researchers found that sleep quantity did have an effect on several areas of cognition for older adults over 98 years old. Lower scores reported for the MMSE (0.073 compared to -0.098), CVLT (-0.081 compared to -0.361), and TMT B (9.281 compared to 8.047) correlated with longer sleep duration. These results indicated that longer sleep duration in older adults was associated with “poorer global cognition, memory, and executive function”. However, further research is needed to conclude whether sleep duration is “a risk factor or a result of poor cognition in advanced age” [4].
Another study in the 90+ Study is on the benefits of exercise in the middle ages. Falling is a great risk for injuries in the older population. 1536 members of a California retirement community, who were originally part of The 90+ Study’s Leisure World Cohort Study (LWCS), were asked about their falls and physical activity during their involvement in LWCS. All participants were 90 years and older. The participants were categorized by the number of falls (1, 2, 3, 4 or more), severity of the fall (no injury, minor injury, moderate injury, or severe injury), reason for most severe fall (dizziness, tripping, loss of balance, or other), and medical attention for most severe fall (none, clinic/doctor office visit, emergency room visit, or hospitalized). This was compared to the participants’ amount of physical activity during their 60-70s (none, 15 minutes per day, 30-45 minutes per day, or 1+ hour per day). The researchers were aiming to find a relationship between the participants’ physical activity in their middle-ages and their current fall rate. It was found that those who moderately exercised during their 60-70s had a lower risk of falling by the age of 90 and beyond. The risk of falls (any falls against no falls) decreased from 1.00 (no exercise as the reference) to 0.83 with 15 minutes a day, to 0.69 with 30-45 minutes a day, and 0.71 with 1 or more hours a day. Furthermore, the risk of repeating falls (2 or more falls against no falls) decreased from 1.00 (no exercise as the reference) to 0.91 with 15 minutes a day, 0.65 with 30-45 minutes a day, and 0.66 with 1 or more hours a day. The limitations of this study include the limits of retrospective data in analysis and the lack of diversity within the study (99% Caucasian participants). The researchers encourage more studies in the same area for non-white and lower socio-economic oldest-old populations [4].
Through their research, Kawas and Corrada demonstrated that there are several habits that have helped the oldest-old maintain their health. These studies have found that older individuals who sleep longer time durations and who were active in their middle age tend to live longer. These habits have been shown to benefit them during their old age, and perhaps the youth may also be able to increase their longevity by following these habits. By these two studies alone, sleep and exercise have been shown as two vital aspects in living a long life. As college students, these two areas are often the most difficult to maintain. Yet, as shown in research, by changing our lifestyles now, it may benefit us in the long run.
References:
[1] “USC Gerontology.” Master’s Degree in Gerontology Online, gerontology.usc.edu/resources/infographics/americans-are-living-longer/.
[2] “The 90 Study.” UCI MIND, 9 Oct. 2018, www.mind.uci.edu/research-studies/90plus-study/.
[3] O’Shea, A., Cohen, R. A., Porges, E. C., Nissim, N. R., & Woods, A. J. (2016). Cognitive Aging and the Hippocampus in Older Adults. Frontiers in Aging Neuroscience, 8: 298.
[4] Sabeti, S., Al-Darsani, Z., Mander, B. A., Corrada, M. M., & Kawas, C. H. (2018). Sleep, hippocampal volume, and cognition in adults over 90 years old. Aging Clinical and Experimental Research, 30: 1307-1318.
[4] Paganini-Hill, A., Greenia, D. E., Perry, S., Sajjadi, S. A., Kawas, C. H., & Corrada, M. M. (2017). Lower likelihood of falling at age 90 is associated with daily exercise a quarter of a century earlier: The 90 Study. Age and Ageing,46: 951-957.