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

Full article: http://www.medscape.com/viewarticle/517382?src=mp

Abstract and introduction only...

"Abstract

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.

Introduction

Poor cognitive functioning is a predictor of mortality at all ages[1-5]
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.[6-12] 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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