JAMA. 2004;292:1454-1461.
Background
Efforts to reduce the risk of dementia may be most successful at the earliest stages of disease development. It has been suggested that physical activity may reduce the risk of early cognitive decline and late-life poor cognition. Walking is one of the most common and most practical leisure-time physical activities practiced by older adults, yet little is known regarding the potential benefits of walking on cognitive function.
Objective
To examine the relation of long-term regular physical activity, including walking, to cognitive function.
Methods
A total of 18,766 women from the Nurses Health Study reported participation in leisure-time physical activities beginning in 1986. For each activity, energy expended in MET-h/wk was estimated. Validated telephone assessments of cognition were administered twice (between 1995 and 2003), and included tests of general cognition, verbal memory, category fluency, and attention. Linear regression was used to estimate adjusted mean differences in baseline cognitive performance and cognitive decline over 2 years, across levels of physical activity and walking.
Results
After adjusting for potential confounders, there was a significant trend of increasingly higher mean scores on all the cognitive measures with higher levels of long-term physical activity. Although the absolute differences in scores appear small, the mean differences seen across quintiles of physical activities were similar to the mean differences observed for women 2-3 years of age apart. Furthermore, there was a significant association between regular physical activity and the odds of cognitive impairment. Even among women who did not participate in vigorous activity but reported walking at an easy pace for at least 1.5 h/wk, there were significantly higher cognitive scores seen when compared with those who reported walking <38 min/wk.
Conclusions
This is a large prospective study showing that long-term regular physical activity is associated with higher levels of cognitive function and a 20% lower risk of cognitive decline. This association was not restricted to women engaged in vigorous activities, as walking at least 1.5 h/wk was also associated with better cognitive performance. Suggested mechanisms for benefit include improvement in the brain's vascular health (by improving blood pressure, promoting endothelial function, etc) and direct effects on brain neuronal structure.
Comments
It should be noted that this study assessed cognitive function, and the authors did not assess for the development of dementia in this cohort. Nevertheless, decrements in cognition have been shown to predict the development of dementia. This study showed that regular physical activity favorably influences late-life cognitive function. This study gives yet another reason for adopting an active lifestyle.