Geda YE, Roberts RO, Knopman DS, Christianson TJ, Pankratz VS, Ivnik RJ, Boeve BF, Tangalos EG, Petersen RC, Rocca WA.
Physical exercise, aging, and mild cognitive impairment: a population-based study.
Arch Neurol. 2010 Jan;67(1):80-6.
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This study presents cross-sectional associations between midlife and late-life physical activities and MCI diagnosis in a population-based study. The associations were significant for moderate-intensity exercise but not for light or vigorous exercise.
The study adds to an accumulating literature of the association between physical activity and cognition in the elderly. It is derived from a well-known population-based study and the methodology and presentation are exceptional.
The major limitation of the study is its cross-sectional character, which raises questions about causality-directionality of the associations. It is possible that MCI subjects just exercise less at present and hence report less moderate exercise in the past, too, which raises the possibility of reporting bias. It would be important to partially examine the validity of the responses using informant sources, too. Most likely the authors plan to perform longitudinal analyses in the near future (that will partially address the above issue).
The absence of a dose-response effect, i.e. even lower MCI rates in the vigorous physical activity group, is of some concern; its presence would further increase confidence in the finding.
This study correlates exercise with decreased odds of developing MCI, which suggests a protective effect of exercise, especially moderate exercise. The observation that moderate exercise performed at either mid- or late life decreased the odds of having MCI is similar to studies with animal models showing that exercise beginning late in life is still beneficial for improving/protecting cognitive function (Nichol et al., 2007). These data are important for showing that exercise can be a valuable intervention in the treatment of cognitive impairment even after symptoms have begun. It will also be important to determine the impact of exercise in combination with dietary factors, which may also have beneficial or detrimental influences.
Nichol KE, Parachikova AI, Cotman CW.
Three weeks of running wheel exposure improves cognitive performance in the aged Tg2576 mouse.
Behav Brain Res. 2007 Dec 3;184(2):124-32.