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Physical activity reduces risk of cognitive decline

 

While studies have suggested that greater physical activity is associated with less cognitive decline, their design flaws (e.g. small sample sizes and short follow-up periods) limit the conclusions that can be drawn from them. This study examines the association between physical activity and cognitive decline addressing the limitations of previous research.

Bottom line

Women with higher levels of physical activity are between 26% and 34% less likely to develop cognitive decline.


Reference

K Yaffe et al. A prospective study of physical activity and cognitive decline in elderly women. Archives of Internal Medicine 2001 161: 1703-1708.

Study

Participants were 5,925 predominantly white women, aged at least 65 years, who were recruited from four US clinical centres. They were without cognitive impairment or physical limitations at the start of the study. The women were interviewed and examined at the initial visit (1986 to 1988). Information was collected on demographics, health behaviours, comorbid health conditions (e.g. stroke, myocardial infarction, hypertension), overall health, functional status and depression. They were followed for six to eight years.

Cognitive performance (including concentration, language and memory) was measured using a modified Mini-Mental State Examination. The test has a potential range of 0 to 26; cognitive decline was defined as a decrease of three or more points from the initial visit to the six or eight year follow-up.

Physical activity was measured by (i) blocks walked per week (1 block equals approximately 160 m) and (ii) by total kilocalories expended per week in blocks walked, stairs climbed and recreational physical activities. Participants were divided into quartiles of physical activity.

Results

The median numbers (and ranges) of blocks walked per week in the quartiles were as follows: lowest 7 (0 to 22); second 28 (23 to 49); third 77 (50 to 112); and highest 175 (113 to 672). Kilocalories expended per week (median and ranges) were as follows: lowest 336 (0 to 615); second 936 (616 to 1,323); third 1,773 (1,324 to 2,414); and highest 3,469 (2,415 to 17,531). Women in the highest physical activity quartiles were younger, more educated, more likely to be taking oestrogen, more likely to drink alcohol, less likely to smoke, had fewer comorbid medical conditions, had a lower body mass index, lower depression scores and less functional limitations than women in the lower quartiles.

Women with a greater physical activity level were less likely to develop cognitive decline.

These results were adjusted for baseline age, educational level, health status, functional limitation, depression score, stroke, diabetes, hypertension, myocardial infarction, smoking and oestrogen use.

Comment

This study found that moderate as well as strenuous physical activity was associated with decreased risk of cognitive decline. Examples of moderate activity included playing 18 holes of golf once a week, playing tennis twice a week or walking 1.6 km (1 mile) a day.

The benefits of exercise are extensive and this study gives us another very good reason to maintain a moderate level of physical activity throughout our lives.