Leng Y, Blackwell T, Cawthon PM, et al. - Researchers conducted this cohort study to explore the connection between rest-activity rhythm and the risk of incident Parkinson disease (PD) and if this connection is independent of nighttime sleep disturbances. This investigation was carried out between December 1, 2003 and March 31, 2005. The risk of incident PD increased significantly with reducing circadian amplitude, mesor, or robustness in this longitudinal study of 2,930 community-dwelling older men (mean [SD] age, 76.3 [5.5] years) without PD at baseline. Compared to vs those in the highest quartile, participants in the lowest quartile for these measures had nearly three times the risk of developing PD. Even after adjustment for nighttime sleep disturbances and duration, the association remained in the lowest vs the highest quartile. According to findings, reduced circadian rhythmicity was related to a higher risk of incident PD, indicating that it could be a significant prodromal feature for PD. More studies are required to see if circadian disruption could also be a risk factor for PD and whether interventions to enhance circadian function have an effect on PD risk.