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Moderate Exercise Linked to Better Executive Function in Older HIV+ People
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4th International Workshop on HIV and Aging, October 30-31, 2013, Baltimore
Mark Mascolini
Moderate physical activity improved odds of lower neurocognitive impairment, particularly as measured by executive function, in a study of 80 older HIV-positive people by researchers at the University of California, San Diego (UCSD) [1]. Intense physical activity did not have this effect.
Randomized trials show that exercise improves cognition in the general population. In people with HIV, previous work by these investigators in a group of 83 self-reported exercisers and 252 nonexercisers found that exercisers were more than twice as likely to have a lower (better) global neurocognitive impairment score than nonexercisers (odds ratio 2.63) and that exercise was associated with better working memory and information-processing speed [2].
The new study involved 80 HIV-positive people in the Successful Aging Seniors With HIV (SASH) study, all between 50 and 70 years old. SASH members undergo a battery of neurocognitive tests encompassing seven domains. Study participants self-reported physical activity on an examiner-administrated International Physical Activity Questionnaire (IPAQ), which queries people on frequency and duration of walking, moderate physical activity, and vigorous physical activity over the past 7 days. IPAQ yields a continuous score based on minutes/week x intensity for each activity level.
Study participants averaged 58.4 years in age (+/- 6.8); 68 (85%) were men and 65 (81%) were white. Years of education averaged 14.4. Seventy-eight people (97.5%) were taking antiretroviral therapy, and 93% had an undetectable viral load. Current and nadir CD4 counts averaged 585 and 135.5.
Almost two thirds of participants (64%) had a lifetime diagnosis of major depressive disorder, and 17.5% had a current major depressive disorder diagnosis. Nearly two thirds (62.5%) had a lifetime substance use diagnosis, but only 5% had a current substance use diagnosis. Thirty-four people (42.5%) met criteria for global neurocognitive impairment, a rate in line with other studies of HIV-positive people.
Proportions of study participants reporting physical activity in the past week were 53.8% for any vigorous physical activity, 55% for any moderate physical activity, and 90% for any walking. Median minutes per week were 60 for vigorous activity, 42.5 for moderate activity, and 210 for walking. Univariate analysis identified a trend between the moderate physical activity IPAQ score and global neurocognitive impairment--with a higher score linked to a lower chance of impairment (P = 0.06).
Next the UCSD team assessed how IPAQ scores for physical activity correlated with individual neurocognitive domains. Only one significant association emerged: IPAQ score for moderate physical activity was significantly higher in 54 people with normal executive function than in 26 people with impaired executive function (P = 0.03, effect size 0.54). In various multivariate models, factors that differed between the impaired and unimpaired group--such as race and current major depressive disorder--did not better explain the association between moderate physical activity and executive function.
IPAQ score for walking or vigorous physical activity did not differ significantly between people with normal or impaired executive function. Why moderate but not vigorous physical activity had a beneficial association with executive function remains unclear. The investigators suggested that over-reporting of intense physical activity on the IPAQ may explain the lack of association.
The UCSD team proposed two mechanisms for the positive association between moderate physical activity and better executive function: (1) Physical activity may directly affect neurogenesis, and/or (2) physical activity may have an indirect effect by reducing risk factors such as vascular morbidity. The researchers believe their findings point to a need for intervention studies to determine whether physical activity is causally related to better cognition and to identify neural mechanisms that may explain this effect.
References
1. Fazeli PL, Dufour C, Marquine MJ, et al. Moderate physical activity is associated with better executive functioning in older adults with HIV. 4th International Workshop on HIV and Aging, October 30-31, 2013, Baltimore. Abstract 17.
2. Dufour CA, Marquine MJ, Fazeli PL, et al. Physical exercise is associated with less neurocognitive impairment among HIV-infected adults. J Neurovirol. 2013;19:410-417.
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