Published on: December 17, 2016
by Laurie L. Barclay M.D. for MedScape:
Exercise is well known to improve overall health and reduce the risk for cardiovascular disease and other chronic conditions. However, it has been unclear whether the benefits of exercise extend to brain health as well.
The goal of the double-blind, double-sham Study of Mental and Resistance Training (SMART) trial was to assess the effect of progressive resistance training (PRT) and cognitive training on fitness (VO2peak and muscle strength) in persons with mild cognitive impairment (MCI). In addition, the study examined whether changes in aerobic capacity and strength over 6 months mediated cognitive changes.
One hundred community-dwelling adults aged 55-86 years with MCI were randomly assigned to receive one of four interventions 2-3 days per week for 6 months: PRT and computerized cognitive training, PRT and sham cognitive training (watching nature videos), cognitive training and a sham exercise program (seated stretching/calisthenics), and sham exercise and sham cognitive training. PRT consisted of weight lifting to ≥ 80% of peak strength, with weight progressively increased as strength increased to maintain intensity at 80% of peak strength.
Compared with sham exercise, PRT significantly increased upper, lower, and whole-body strength, as well as percentage change in VO2peak (8.0%). Nearly one half (47%) of all participants assigned to PRT achieved normal cognitive scores after the intervention. Cognitive improvements were significantly associated with higher strength scores, but not with greater VO2peak. Greater lower body strength significantly mediated the impact of PRT on improvements in the cognitive subscale and global domain, but not the executive domain, of the Alzheimer’s Disease Assessment Scale (ADAS). Benefits in global and executive domains were maintained over 18 months.
Study limitations include estimation of VO2peak up to 60 seconds after stopping treadmill exercise, the use of the ADAS-cognitive subscale rather than a comprehensive neurocognitive battery, and possible unmeasured confounding. Nonetheless, these findings suggest that PRT, two or three times weekly at 80% peak strength, may offer cognitive benefits in MCI, mediated by strength gains rather than by improvements in aerobic capacity.
The findings extend those of an earlier study in which ADAS-cognitive subscale improved significantly after PRT and were maintained up to 12 months, but not after cognitive training or sham interventions. In addition, previous results from the SMART trial showed MRI increases after PRT in specific regional brain volumes involved in cognitive processing.Future research should determine whether strength gains mediate these anatomical improvements, explore the physiologic mechanisms underlying the association between strength gains and cognitive benefits, and identify optimal exercise regimens.
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