Exercise as it relates to Disease/Can walking stabilise cognitive function in Alzheimer's Disease?

This is a critical analysis of a research article titled "Walking stabilizes cognitive functioning in Alzheimer's disease (AD) across one year" by Jeanna Winchester, Malcolm B. Dick, Daniel L. Gillen, Bruce R. Reed, Bruce L. Miller, Jared R. Tinklenberg, Dan Mungas, Helena Chang Chui, Douglas R. Galasko, Linda J. Hewett and Carl W. Cotman (2012)

What is the background to this research?
Alzheimer's disease is the 6th leading cause of death in the United States and the only disease in the top 10 that cannot be prevented or cured. The disease impairs cognitive and behavioural functioning, which can have severe impacts on the daily activities of the 1 in 10 Americans aged over 65 who live with the disease, as well as their friends, families and caregivers. This research article is a part of the movement to find treatments to improve the quality of life for the victims of Alzheimer's disease. With the numbers of people affected by this disease expected to rise it is crucial that research in this area is progressed.

The study has called on several epidemiological studies that suggest physical activity may be beneficial to cognitive functioning in older adults. As more specific preliminary support, the article has referenced 2 randomised controlled trials that garnered positive effects of aerobic exercise in adults with Mild Cognitive Impairment. They used this evidence to create the assumption that the possibility of exercise improving cognition and/or reducing the rate of decline in mild-to-moderate Alzheimers disease exists.

Where is the research from?
The research was conducted by 9 out 10 of The Alzheimer's Disease Research Centers of California, located at large medical centres around the state. The centres insist key personnel were trained to ensure reliability and validity of the results obtained. The centres are funded by the California Department of Health which may result in increased pressure to find results so funding continues. All authors work at the Alzheimer's centres that conducted the research and have many previous publications in cognitive ability.

What kind of research was this?
The research conducted in this article was a case-control observational study. This kind of research requires less resources to organise however provides less evidence than a randomised control trial.

What did the research involve?
The study took place over a year time period with participants and/or informants completing baseline surveys and follow-up surveys a year later. The research used 7 measures attempting to discover a relationship in mood and exercise in mild-to-moderate Alzheimer's disease patients. Staff members involved in the study received training to administer the following measures, which focussed on different aspects of cognitive functioning and exercise:


 * Yale Physical Activities Survey for Older Adults (YALE) - amount of time the patient engaged in physical activity on a weekly basis.
 * Geriatric Depression Scale (GDS) & Profile of Mood States (POMS) - common measure of depression in geriatric populations and mood status.
 * Blessed-Roth Dementia Rating Scale (BRDRS) & Functional Abilities Questionnaire (FAQ) - functional abilities of daily life.
 * Neuropsychiatric Inventory (NPI) - behavioural symptoms based on informants.
 * Mini-Mental State Examination (MMSE) - global cognition such as working memory, executive function, processing speed and attention.

The Mini-Mental State Examination score was the dependent variable of interest while the other questionnaires made up the independent variables.

Limitations

This study was conducted on a relatively large scale, gathering information from 9 different centres around the state of California. This increases the difficulty of collecting data and assembling it together, however they had strategies in place to combat this effect. Ironically, the sample space (N=104) was relatively small compared to other epidemiological studies. Another limitation refers to the potential effect of collecting the data in a dynamic environment such as the Alzheimer's Disease Centers of California. The article admits that the patients evaluated in these environments may report higher levels of vigour-activity than those found in the overall residential population. The most significant limitation to the validity of this research however, is caused by the informant-based questionnaires used to gain the results. Measures were put in place to provide a low probability of bias however the question remains of the bias of the caregivers and the reliability and validity of the questionnaires. Informants were imperative in a study with patients suffering from cognitive impairment. The use of correlation analysis to determine relatedness can also be seen as a limitation.

What were the basic results?
Based on the baseline physical activity questionnaire, the study sample (N=104, age=81±6.54) were divided into two groups of Active (N=84) and Sedentary (N=20). The Active group was further divided in relation to how many hours of walking was achieved per week.

When comparing the results for the Mini-Mental State Examination an obvious difference of global cognitive functioning can be seen at varied levels of physical activity. The Sedentary patients have a serious decline whereas physical activity in the form of walking displays a slowing rate of decline and even stabilisation or improvement in the patients who are involved in ~2 hours of walking activities per week. Other results that were found were a change in mood status with a decrease in vigour-activity and an increase in negative mood states such as anger-hostility and confusion-bewilderment. This produced further analysis and a correlation was found between the Sedentary group and the increase of negative mood states. There was no insurance that a correlation wasn't found between the negative mood states and the physically active patients. This suggests that an emphasis on finding results that suited the researchers' narrative was possible.

What conclusions can we take from this research?
From this research we can suggest that physical activity does have an effect on the rate of decline of cognitive functioning in mild-to-moderate Alzheimer's disease patients. A sedentary lifestyle correlates to an increase in negative mood and decrease in vigour. However, due to the lack of specific data and questionable collection methods, it is unclear what kind of physical exercise and what dose is most beneficial to cognitive functioning.

A recent physiological study supports the claims that exercise is beneficial for brain activity. Although recent systematic reviews, reinforce the concern for the lack of empirical evidence and the need for further understanding of the benefits physical activity can have on Alzheimer's sufferers.

Practical advice
The evidence found in this research study cannot condone official exercise protocols to guarantee a change in the rate of decline for Alzheimer's disease patients. However, the findings should support further research into the relationship with greater structure design and specific focus on dosage. Although it hasn't been formally specified as a treatment, Alzheimer's patients shouldn't disregard physical activity as a method of stimulating cognitive function and potentially decreasing the rate of decline.

Further readings:
 * Alzheimer's Association - https://www.alz.org/alzheimers-dementia/facts-figures
 * Physical Activity and Alzheimer’s Disease: A Systematic Review - https://academic.oup.com/biomedgerontology/article/72/6/733/2797763