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 = .010), equivalent to -0.3 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. Statement of Significance This study suggests that periodic limb movements during sleep (PLMS) may be related to early cognitive vulnerability and could represent an early marker of accelerated cognitive aging. A higher frequency of PLMS was associated with a steeper deterioration in executive function over about 5 years in community-dwelling older adults, independent of restless legs syndrome symptoms, other sleep conditions, and relevant clinical factors. These findings highlight the need for future research to elucidate the neurobiological mechanisms linking PLMS to accelerated cognitive aging, and to determine whether reducing PLMS could help preserve cognitive health, or whether PLMS primarily represent a marker rather than a direct contributor to cognitive deterioration.