Exercise as it relates to Disease/Physical Activity and Risk of Cognitive Impairment and Dementia in Elderly Persons

This is an analysis of the journal article "Physical Activity and Risk of Cognitive Impairment and Dementia in Elderly Persons" by Laurin et al (2001)

What Is The Background To This Research?


The number of people with dementia and Alzheimer's disease is rising; Memory problems are fairly common with aging however there is a difference between normal changes in memory and those changes associated with Alzheimer's and related diseases. These tend to usually begin gradually and in most cases worsen over time. Dementia is a major health concern for the elderly; it is common, costly and highly age related.

Although such diseases cannot be stopped or reversed there are a number of medications and preventative measures that can help treat some of the symptoms and delay their onset however little is known about the effects of environmental factors such as lifestyle habits and physical activity (PA).

PA has a number of health benefits and is effective at preventing a number of chronic diseases including coronary artery disease, diabetes, stroke and osteoporosis however the evidence that PA may delay cognitive impairment is inconsistent.

There have been a few epidemiological studies that have looked into the role of PA on cognitive impairment and dementia in elderly people. It has been proposed that exercise may be beneficial for dementia and for Alzheimer’s Disease (AD) in particular however this has not been consistently replicated. The aim of this study is to assess the association between PA and the occurrence of dementia and cognitive loss based on a representative sample of the elderly Canadian population.

Where Is The Research From?
The research for this study comes from a community sample of the Canadian Study Of Health And Aging (CSHA) which is a national, multicentre, prospective cohort study focusing on the frequency, occurrence and risk factors for dementia and AD in elderly Canadians.

What Kind Of Research Was This?
This research is a qualitative, large scale, prospective cohort study based on a representative sample of the elderly Canadian population.

What Did The Research Involve?
Participants

In 1991-1992, a sample of men and women over the age of 65 were randomly selected from a population based listing from 36 urban and surrounding rural areas in all 10 Canadian provinces. Out of an initial 10263 sample, 9008 participants made up the initial pool of subjects with 4615 participants completing a 5-year follow up.

Method

Firstly all subjects were interviewed to gain their own perceived health status, general condition and functional ability based on an altered version of the older Americans Research survey scale. Participants were then tested for dementia using an adapted mini mental state examination and given either a positive or negative result. All subjects without dementia were asked to complete a self administered risk factors questionnaire reporting on demographic characteristics, work and environmental exposures, lifestyle and medical and family histories. Participants who tested positive and a random sample of those who tested negative were then screened for hearing, vision impairment and had information collected about their medication schedule and medical and family histories. Next a physician completed a standard physical and neurological test and a psychometrist administered a neuropsychological test battery to all subjects if possible. A neuropsychologist according to the Diagnostic and Statistical Manual Of Mental Disorders then interpreted the results independently. The diagnosis was as follows: no cognitive impairment, cognitive impairment or no dementia, AD (probable or possible) according to the National Institute Of Neurological Disorders and Stroke – AD and Related Disorders Association. A follow up was carried out in 1996-1997; all subjects who could be contacted and agreed to participate in the second wave were re-interviewed to determine changes in health status and functional ability following an average of a 5-year period. Subjects were administered the same diagnostic process including the screening and clinical evaluation from the initial wave. Diagnosis was then re-evaluated without the knowledge of the initial studies diagnosis. Exercise data was collected when subjects were not demented which represents a sample for earlier activity. The level of PA was assessed using the risk factor questionnaire regarding frequency and intensity and given a PA score of low, medium or high. Subjects who reported no regular exercise were used as a reference category.

What Were The Basic Results?
PA was associated with lower risks of cognitive impairment, AD and any type of dementia when compared with no exercise. Higher levels of PA had a reduced risk and offered greater protection and that any exercise is better than no exercise.

Based on the exercise data collected when subjects were not demented, a large proportion of the controls participated in no PA, with the majority of the sample participating in a moderate amount of PA.

How Did The Researchers Interpret The Results?
The researchers interpreted the results based on self-reports of frequency and intensity of exercise and compared this to the prevalence and incidence of dementia and other related cognitive diseases for each subject. The results were based on a large sample using a thorough prospective design.

Although the results were relatively strong, the method was based on self-report which meant that there could have been the potential for bias making the study less reliable.

What Conclusions Should Be Taken Away From This Research?
This study showed that regular PA has a protective effect on the risk of dementia and other related cognitive diseases, in particular AD in a sample size of the Canadian elderly population. This was mainly observed in women and showed that increasing levels of PA were associated with a decreased risk of cognitive impairment. This study also suggests that participating in regular exercise, among other things, may delay or prevent the onset of cognitive impairment and dementia. The stronger association for women could be related to an interaction between exercise and hormone balance. Exercise could also be viewed simply as a marker of good health, which in itself has been related to a lower risk of cognitive impairment and dementia.

What Are The Implications Of This Research?
This study has shown that engaging in regular PA can have a number of positive effects on cognitive health. Although this research was based on self-report and further support and research is needed it suggests that exercise could play an important part of preventing and delaying cognitive impairment in the elderly population.

Since this study was published there has been a lot of research that associates PA with a decreased risk of AD and other related cognitive diseases. Previously, the effect of exercise on cognitive processes had been mainly assessed by the use of pen and paper and computer based tests. Now however, with the advancement of technology, neuroimaging has provided significant evidence to support the association between PA and cognitive loss.

PA has been proven to boost brainpower and activate more parts of the brain, which is important as the cells will eventually start to die if not used. It has also been found that exercise reduces the loss of brain tissue, grey matter and hippocampal volume, which is vital for memory. It facilitates neuroplasticity, stimulates the formation of new neurons and increases brain connectivity/activation and improves blood flow. In addition to this functional brain MRI’s, during cognitive tasks have documented significant improvements in cognitive networks with PA.

Further Readings For more information and further research please refer below :

Physical Exercise as a Preventive or Disease Modifying Treatment of Dementia and Brain Aging -http://www.mayoclinicproceedings.org/article/S0025-6196(11)65219-1/fulltext

PA, Diet, and Risk Of Alzheimers Disease - http://jama.jamanetwork.com/article.aspx?articleid=184383

Exercise builds brain health: key roles of growth factor cascades and inflammation - http://www.abc.net.au/catalyst/stemcells/images/Cotman2007TrendsNeurosci.pdf

Effect of Physical Activity on Cognitive Function in Older Adults at Risk for Alzheimer Disease -http://zh9bf5sp6t.scholar.serialssolutions.com/?sid=google&auinit=NT&aulast=Lautenschlager&atitle=Effect+of+physical+activity+on+cognitive+function+in+older+adults+at+risk+for+Alzheimer+disease:+a+randomized+trial&id=doi:10.1001/jama.300.9.1027&title=JAMA+:+the+journal+of+the+American+Medical+Association&volume=300&issue=9&date=2008&spage=1027&issn=0098-7484