Sleep Medicine: X · Published 2026-02-04 · DOI 10.1016/j.sleepx.2026.100175
Objectives: This cross-sectional study, based on the two-process model of sleep regulation, explored the nonlinear relationships and interactions among nocturnal sleep duration, daytime napping, sleep quality, and mild cognitive impairment (MCI) in middle-aged and older Chinese adults. Methods: Data from 7480 participants in the 2018 wave of the China Health and Retirement Longitudinal Study (CHARLS) were analyzed. Restricted cubic splines modeled dose-response relationships, and stratified logistic regression assessed subgroup variations. Models were adjusted for sociodemographic, lifestyle, and clinical covariates. Results: The lowest odds of MCI were observed among participants reporting 6–8 h of nocturnal sleep and 30–60 min of daytime napping. Short (<6 h) and long (>8 h) sleep durations, along with prolonged napping (≥90 min), were linked to higher odds of MCI. Sleep quality modified these associations: poor sleep quality elevated the odds of MCI, especially among long sleepers (OR = 1.88 vs. 1.33 for good sleep quality). Among short sleepers (<6 h), 30–60 min naps were associated with lower odds of MCI (OR = 0.72). Conclusions: These findings indicate that, in this cross-sectional sample, 7–8 h of nocturnal sleep combined with 30–60 min of daytime napping were associated with better cognitive status, whereas long sleep with poor sleep quality was associated with higher odds of impairment. These observational associations, considered within a circadian–homeostatic framework, are hypothesis-generating and warrant confirmation in future longitudinal and interventional studies.
Abstract from DOAJ. Public domain (CC0 1.0).
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