Effects of Physical Activity on Cognitive Functioning in Middle Age: Evidence From the Whitehall II Prospective Cohort Study

Archana Singh-Manoux, PhD; Melvyn Hillsdon, PhD; Eric Brunner, PhD; Michael Marmot, PhD, MBBS, FFPHM, FRCP

Disclosures

Am J Public Health. 2005;95(12):2252-2258. 

In This Article

Abstract and Introduction

Objectives: We examined the association between physical activity and cognitive functioning in middle age.
Methods: Data were derived from a prospective occupational cohort study of 10 308 civil servants aged 35-55 years at baseline (phase 1; 1985-1988). Physical activity level, categorized as low, medium, or high, was assessed at phases 1, 3 (1991-1994), and 5 (1997-1999). Cognitive functioning was tested at phase 5, when respondents were 46-68 years old.
Results: In both prospective (odds ratio [OR] = 1.65; 95% confidence interval [CI] = 1.30, 2.10) and cross-sectional (OR = 1.79; 95% CI = 1.38, 2.32) analyses, low levels of physical activity were a risk factor for poor performance on a measure of fluid intelligence. Analyses aimed at assessing cumulative effects (summary of physical activity levels at the 3 time points) showed a graded linear relationship with fluid intelligence, with persistently low levels of physical activity being particularly harmful (OR = 2.21; 95% CI = 1.37, 3.57).
Conclusions: Low levels of physical activity are a risk factor for cognitive functioning in middle age, fluid intelligence in particular.

Poor cognitive functioning is a predictor of mortality at all ages[1,2,3,4,5] and, as such, can be seen as a marker of general health status. Leisure-time physical activity has been shown to have a beneficial impact on cognitive functioning among older adults.[6,7,8,9,10,11,12] It also appears to offer protection against cognitive impairment and dementia in the elderly.[13,14] A meta-analysis that focused on randomized aerobic fitness intervention trials with intervention periods of less than a year showed fitness training to be associated with improved cognitive performance.[15]

Despite the wealth of evidence in this domain, questions remain. The most important question relates to whether the association between physical activity and cognitive functioning is specific to old age or evident earlier in adulthood. It also remains unclear whether benefits of physical activity over several years have a cumulative effect on cognitive functioning. This issue is relevant for the elaboration of public health messages on leisure-time physical activity. Cross- sectional studies are not adequate to model long-term effects of physical activity, and, because of their relatively short intervention periods (typically 3-4 months), the same is true of studies involving experimental designs.

We examined the association between physical activity over a span of several years and cognitive functioning in middle age. We contend that it is important to examine the relationship between physical activity and cognitive functioning in younger, healthier populations and to assess whether subtle neuropsychological deficits are evident among members of these age groups who are not physically active. Poor cognitive performance in early adulthood or in middle age is clinically relevant, given studies showing that individuals with mild cognitive impairment progress to clinically diagnosed dementia at an accelerated rate.[16,17]

We also sought to identify specific cognitive domains that might be particularly vulnerable to low levels of physical activity. Different studies have revealed beneficial effects of physical activity on fluid intelligence,[6,7] visuospatial performance,[10] reaction time,[8] and memory.[18,19] However, multiple cognitive domains often have not been examined in the same study. Establishing specific associations would enable elaboration of the pathways and mechanisms through which physical activity influences cognitive functioning.

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