Does exercise demonstrate a dose-dependent benefit with cognition in Parkinson's disease?

Background: Exercise confers motor benefits in Parkinson's disease (PD) and may even have disease modifying effects. While the impact of exercise on motor symptoms and quality of life is well-studied in PD, its relationship with cognitive performance warrants further attention.

Methods: In people with PD, self-reported exercise information was quantified using the Rapid Assessment of Physical Activity (RAPA). Cognitive performance was assessed using the symbol digit modalities test (SDMT) and Stroop tests. The association between test performance and intensity of physical exercise, as measured by the RAPA, was assessed using linear regression, adjusting for covariates of age and duration of Parkinson's disease.

Results: 172 participants completed Stroop testing and 181 completed SDMT in both medication "off" and "on" states. Compared with participants reporting no exercise, those with mild activity (RAPA frequency/duration score 2-3) performed better on the SDMT (β = 1.31, p = 0.01) and Stroop color naming (β = 9.19, p = 0.02). Highly active participants (RAPA frequency/duration score 6-7) scored significantly higher than those with moderate activity (RAPA frequency/duration score 4-5) on the SDMT (β = 1.44, p < 0.01) and Stroop color naming (β = 4.66, p = 0.03).

Conclusion: Higher self-reported physical activity levels were associated with higher cognitive performance in a dose-dependent fashion in both the off-medication and on-medication states. The greatest difference in cognitive performance was seen between those reporting no exercise and those reporting at least some activity, suggesting that even small amounts of physical activity can benefit cognition.