Exercise as it relates to Disease/The association between walking and future risk of dementia in older men

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The following analysis is obtained from the journal article " Walking and Dementia in Physically Capable Elderly Men" by Abbott et al., 2004[1]

What is the background to this research?[edit]

From 1965-68 the Honolulu Heart program was established. It began following up 8006 men who were of Japanese ancestry and resided on the island of Oahu, Hawaii. The study was to detect the development of cardiovascular disease in participants. Examinations were carried out between 1991-93. The Honolulu-Asia Aging Study was created as an extension of the Honolulu Heart Program, for the study of neurodegenerative diseases and cognitive function in elderly persons.[1] Physical factors that are associated with the risk of dementia remain mostly undefined. However evidence suggests that physical activity may be associated with the clinical expression of dementia [1][2][3] Whether there is a direct association with low intensity exercise such as walking and dementia is not quite yet known. One study found that in a large cohort of women, those who took the initiative to walk more had notable smaller declines when undertaking a Mini-Mental State Examination over a 6-8 year period of follow-ups.[2] It must be noted that other studies describe relations between physical activity and dementia as weak, whilst also presenting contrasting evidence for the importance and need for cognitive activities for reducing the risk of dementia.[4][5][6] From the literature it appears cognitive activity can be used as a predictor for future dementia, linking this in with physical activity may make it harder to detect an association between walking and dementia. Looking at walking and its association with reduced risk for dementia can be seen as important as it is a physical activity that most people can undertake as it requires no equipment, it's practicality would appeal to a lot of people. Taking this into consideration the main aim of this study was to examine the link between walking and future risk of dementia.[1]

Where is the research from?[edit]

Abbott et al., 2004 [1] The research was conducted on the island of Oahu, Hawaii. Hawaii is renowned for it's warm climate which could be considered a contextual constraint of the study as the ability to walk in Hawaii year round could be easier than other countries such as Australia which can get quite cold during the winter time making it hard for people to adhere to exercise activities outdoors during these months.

What kind of research was this?[edit]

The study undertaken was a prospective cohort study. It was a longitudinal cohort study that followed participants over a number of years. Longitudinal studies are observational in nature, researchers do not interfere with subjects through out the course of the study. Researchers will examine the subjects over a period of time via follow-ups, this process can last several years. The main benefit of longitudinal studies is that they are able to identify changes in the characteristics of the target population as a group as well as them as individuals over a period of time, this allows the study to develop a sequence of events.

What did the research involve?[edit]

A population sample size of 3734 participants was used in the study that were men aged between 71–93 years. Findings from the study are based on follow-ups which looked for incident dementia by neurological assessment, the Cognitive Abilities Screening Instrument (CASI) was used for this. It is a measure that has been validated for the use in cross-cultural studies.[7] Two repeat examinations were conducted in the years 1994-96 and 1997-99. When diagnosing dementia amongst participants a number of factors were taken into consideration. History of family members was obtained, neuropsychological and neurological examinations were also undertaken. Participants who were diagnosed with dementia met the criteria that was based on the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition.[8] People that were found to have dementia during the initial assessment period were excluded from the study. To be eligible for the study participants had to be deemed as physically capable, this was determined by a Physical Activity Index[9][10] which revealed if participants undertook light-moderate activities in a typical 24-hour period, "walking on ground level" and "gardening or carpentry" were used as references to help distinguish between light and moderate exercise.[1] To get an idea of how much walking the participants were undertaking daily all participants were asked at the beginning of the follow-ups (held between the years 1991-93) to state on average the amount of walking they did each day. During the follow-ups participants were also required to undertake a battery of tests. These tests included being able to walk 3m with a normal gait, heel and toe walking, balance was assessed through means of getting the participant to stand from a seated position. A weighted score was then obtained by averaging each item, which then formed a "physical performance score".[11] A higher physical performance score indicated better physical function than that of a lower score. The main limitation of the study was the use of self-reported activity via recalls. This method can be prone to bias which can inhibit the results as participants can report information that may not be completely truthful.

Basic results?[edit]

From the follow-ups 158 people were found to have dementia. It was found that men who walked <0.25 miles a day experienced 1.8 times more risk of dementia compared to those who walked more than 2 miles a day (17.8 vs 10.3/1000 person-years).[1] An additional risk was also found to be present for those who walked between 0.25–1 miles a day compared to those who walked >2miles a day ( 17.6 vs 10.3/1000 person-years).[1]

How did the researchers interpret the results?[edit]

The researchers interpretation of the results from the study was that physically capable men who walk regularly have a reduced chance of developing dementia. The researchers make note that the association between walking and dementia might be influenced by a number of factors that have not been researched yet which include diet, brain plasticity, functional brain reserves and environmental and lifestyle exposure.[12][13] Examining a population that resides in Hawaii that is known for having a mild climate gives the participants the advantage of being able to walk more regularly and could contribute to the reason why the association between walking and dementia hasn't been observed elsewhere.[1] Self-reported activity via recall was used in this study. This method can be susceptible to bias in results as participants can tend to give information that might not be completely truthful, this needs to be taking into consideration when interpreting the results.

What conclusions can we take from this research?[edit]

The conclusions that can be drawn from this study is that walking is linked to a reduced risk of dementia. Promoting physically active men to lead active lifestyles is important as the elderly want to maintain their independence for as long as possible, walking and other forms of exercise can help them achieve this. Recent studies also support the notion that increased exercise is associated with reduced risk of dementia and that taking part in a diverse range of physical activities is beneficial.[14][15]

Practical advice[edit]

This study and past evidence suggest that walking and regular exercise is associated with a reduced risk of dementia. To maximize benefits from exercise/walking programs adherence must be maintained long term. Disabilities and physical impairments could restrict a person's ability to undertake walking, alternate methods of exercise need to be considered if this is the case.

Further reading[edit]

References[edit]

  1. a b c d e f g h i Abbott R, White L, Ross G, Masaki K, Curb J, Petrovitch H. Walking and Dementia in Physically Capable Elderly Men. JAMA. 2004;292(12): p.1447-1453.
  2. a b Yaffe K, Barnes D, Nevitt M, Lui L, Covinsky K. A prospective study of physical activity and cognitive decline in elderly women: women who walk. Arch Intern Med.2001;161:p.1703-1708.
  3. Kramer A, Hahn S, Cohen N, Banich M, McAuley E, Harrison C, Chason J, Vakil E, Bardell L, Boileau R, Colcombe A. Ageing, fitness and neurocognitive function. Nature.1999;400:p.418-419
  4. Verghese J, Lipton R, Katz M, Hall C, Derby C, Kuslansky G, Ambrose A, Sliwinski M, Buschke H
  5. Wilson R, Mendes De Leon C, Barnes L, Schneider J, Bienias J, Evans D, Bennett D. Participation in cognitively stimulating activities and risk of incident Alzheimer disease. JAMA.2002;287: p.742-748
  6. Wilson R, Bennett D, Bienias J, Aggarwal N, Mendes De Leon C, Morris M, Schneider J, Evans D. Cognitive activity and incident AD in a population-based sample of older persons. Neurology.2002;59: p.1910-1914.
  7. Folstein M, Folstein S, McHugh P. Mini-Mental State: a practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res.1975;12: p.189-198.
  8. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition. Washington, DC: American Psychiatric Association; 1987
  9. Kannel W, Sorlie P. Some health benefits of physical activity: the Framingham Study. Arch Intern Med.1979;139: p.857-861.
  10. Abbott R, Rodriguez B, Burchfiel C, Curb J. Physical activity in older middle-aged men and reduced risk of stroke: the Honolulu Heart Program. Am J Epidemiol.1994;139: p.881-893.
  11. Young D, Masaki K, Curb J. Associations of physical activity with performance-based and self-reported physical functioning in older men: the Honolulu Heart Program. J Am Geriatr Soc.1995;43: p.845-854.
  12. Cotman W, Berchtold N. Exercise: a behavioral intervention to enhance brain health and plasticity. Trends Neurosci.2002;25: p.295-301
  13. Scarmeas N, Zarahn E, Anderson K. et al. Association of life activities with cerebral blood flow in Alzheimer disease: implications for the cognitive reserve hypothesis. Arch Neurol.2003;60: p.359-365
  14. Larson E, Wang L, Bowen J, McCormick W, Teri L, Crane P, et al. Exercise Is Associated with Reduced Risk for Incident Dementia among Persons 65 Years of Age and Older. Ann Intern Med. 2006;144: p.73-81
  15. Podewils L, Guallar E, Kuller L, Fried L, Lopez O, Carlson M. et al. Physical activity, APOE genotype, and dementia risk: findings from the Cardiovascular Health Cognition Study. Am J Epidemiol. 2005; 161: p.639-51