Exercise as it relates to Disease/The Association between Physical Activity and Alzheimer's Disease

The following is a journal article analysis of Physical Activity and Alzheimer's disease course

What is the background to this research?
Dementia is a name for a collection of progressive brain syndromes, which can affect memory, behaviour, thinking, and emotion. Alzheimer's Disease is the most well known form of dementia and accounts for 50-60% of all dementia cases. As of 2015, over 46 million people live with dementia worldwide, and this number is estimated to increase to 131.5 million by 2050.

Many studies have been conducted to show that physical activity can reduce the risk of developing Alzheimer's disease. The aim of this study was to examine whether physical activity can affect the course of Alzheimer's disease. It was hypothesised that physical activity may be associated with a reduced mortality as well as affect rates of cognitive decline in those diagnosed with Alzheimer's disease.

Where is this research from?
This study was conducted at the Columbia University Medical Center in New York. The authors of this study are as follows:
 * Yaakov Stern is a Professor of Clinical Neuropsychology in the Departments of Neurology, Psychiatry, and Psychology, as well as the in Sergievsky Center and the Taub Institute for the Research on Alzheimer’s Disease and the Aging Brain.
 * Ming-Xin Tang is an Associate Professor of Biostatistics at the Columbia University Medical Center.
 * Nicole Schupf, PH.D. is a Professor of Clinical Epidemiology at the Columbia University Medical Center.
 * Stephanie Cosentino, PH.D. is an Assistant Professor of Neuropsychology at the Columbia University Medical Center.
 * Nikolaos Scarmeas, M.D. is Associate Professor of Clinical Neurology at the Columbia University Medical Center.
 * Jose Luchsinger, M.D. is an Associate Professor of Epidemiology and Medicine at the New York Presbyterian Hospital & at the Columbia University Medical Center.
 * Yian Gu, PH.D. is an Assistant Professor of Neuropsychology at the Columbia University Medical Center.

What kind of research was this?
This study was a population-based study, following 357 individuals aged 65 or over.

What did the research involve?
This research involved following 357 individuals and assessing their cognitive and functional declines, as well as mortality rates in individuals with Alzheimer's disease.

Sample and diagnosis
All participants underwent many examinations in order to be considered for this study. At entry, medical and neurological history was examined, and a standardized physical and neurological examination was conducted. All medical charts, CT scans and MRI's were considered. Each individual also participated in an interview which included assessments of heath and function, as well as testing of memory, orientation, language, abstract reasoning, and visual-spatial abilities. Each individual was also given a global summary score on the Clinical Dementia Rating. All the above evaluations were presented to make a consensus diagnosis at a diagnostic conference of neurologists and neuropsychologists. The criteria of the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association were used for the diagnosis of probable or possible Alzheimer's disease. Individuals were then followed at intervals of approximately 1.5 years where the baseline examination and consensus diagnosis was repeated. The 357 individuals chosen for this study had available physical activity evaluations and were non-demented at baseline but then developed Alzheimer's disease in the follow up examinations.

Evaluation
For this study, a modified Godin Leisure time exercise questionnaire was used. The subjects were divided into two subsets, each subset using a slightly different version of this questionnaire. One subset, of 149 individuals, were questioned about their typical number of activities that they engaged in within the most recent two week period. These activities were recorded into 3 different categories: vigorous (aerobic dancing, jogging, playing handball), moderate (cycling, swimming, hiking, playing tennis) and light (walking, dancing calisthenics, golfing, bowling, gardening, horseback riding). These categories were used to create a summary physical activity score for each individual by using the formula number of minutes x number of times x coefficient (9 for vigorous, 5 for moderate, and 3 for light activities which correspond to the metabolic equivalents for the related activities). These scores were then categorized into a 3-level variable according to how much physical activity they engaged in. The second subset of 208 individuals were questioned according to the number of hours during the most recent month in which they engaged in their typical number of activities. A similar procedure was used to create a physical activity score and then categorise the individuals into a 3-level variable.

Limitations
One limitation that was identified was that of the reporting of physical activity, rather than an objective measurement of physical fitness. This is said to be a limitation of the study as an objective measurement of physical fitness may relate to cognitive performance rather than a self reported measurement. Another limitation of the study include that of the ability of those with cognitive decline to accurately report their physical activity.

What were the basic results?
Results of this study show that physical activity does not seem to be associated with the rate of cognitive change, however it does show that physical activity relates to the prolongation of survival of patients with Alzheimer's disease. There also seems to be a relationship with the amount of physical activity, with those having a higher reported physical activity having a gradual reduction in mortality risk.

Physical activity and the rates of Cognitive and Functional Decline
This study found no evidence to suggest that rates of cognitive and functional decline are affected by physical activity.

Physical activity and mortality
As stated previously, this study found that there was a relation between physical activity and mortality rates of individuals with Alzheimer's disease. The extent of these findings were considerable, with individuals who reported some physical activity as opposed to physically inactive individuals, being 43-47% less likely to die. Even more considerable, those who reported much physical activity were found to have a 53-59% reduction in mortality. These percentages translate to a difference of living 5.5-8 years longer as opposed to those physically inactive individuals.

What conclusions can we take from this research?
Conclusions that we can take from this research is that physical activity could be related to prolonged survival in Alzheimer's disease. However no evidence was found as to whether exercise can change the rate of cognitive and functional decline.

Practical advice
Advice that can be taken from this article is that exercise may be a key factor in prolonging survival during the course of Alzheimer's disease. However before beginning exercise, individuals should consult a physician in order to safely begin exercise, as well as determine any risk factors associated with beginning of exercise. Physicians may conduct a pre-exercise screening and any exercise plans should be safe for the individual.

Further information
For further information on Alzheimer's Disease, visit Alzheimer's Australia at https://www.fightdementia.org.au/, or Alzheimer's Disease International at https://www.alz.co.uk/.