Periodic Limb Movements during Sleep, Restless Legs Syndrome, and Cognitive Changes in Older Adults: A Population-Based Longitudinal Study.

Study Objectives To investigate the associations of periodic limb movements during sleep (PLMS) and restless legs syndrome (RLS) symptoms with longitudinal changes in cognitive performance among older adults. Methods We analyzed data from 382 community-dwelling older adults without dementia participating in the HypnoLaus study (mean age: 71.0±4.1 years; 42.9% male). Participants underwent polysomnography and baseline cognitive testing, followed by a second cognitive assessment after 4.7±0.6 years. Individuals were categorized by PLMS index (PLMI) as <15/h (reference), 15-29.9/h, and ≥30/h. Associations between PLMI categories and annualized changes in executive function (Stroop Test), verbal fluency, and verbal memory were examined using multiple linear regression models adjusted for potential confounders. Additional analyses evaluated the role of RLS symptoms and PLMI×RLS symptoms interactions. Results A PLMI ≥30/h was associated with a steeper deterioration in executive function compared with the reference group (B=-0.06 standard deviations [SD]/year, p=0.010), equivalent to -0.30 SD and -1.5 SD declines over 5 years relative to the baseline performance and to the distribution of change scores, respectively. This association was independent of RLS symptoms and other sleep-related conditions. No significant associations were observed between PLMI and changes in verbal fluency or verbal memory. RLS symptoms were not associated with changes in any cognitive outcome, and no PLMI×RLS symptoms interaction was detected. Conclusions High PLMS frequency was independently associated with accelerated deterioration in executive function, suggesting a link between PLMS and cognitive aging. In contrast, RLS symptoms showed no association with changes in cognitive function.