Association of combined nighttime – midday napping patterns with possible sarcopenia among older Chinese adults: a cross-sectional analysis of CHARLS

Objective To investigate the association between combined nighttime and midday napping patterns and possible sarcopenia in the Chinese elderly population to provide evidence for developing targeted sleep health management strategies.Method This study use data from the 2015 China Health and Retirement Longitudinal Study (CHARLS) and included 7,003 elderly participants (≥60 years). Possible sarcopenia was defined according to the Asian Working Group for Sarcopenia 2019 consensus (AWGS 2019). The dose-response relationship between sleep duration and possible sarcopenia was analyzed using a Restricted Cubic Spline (RCS) model. Based on the RCS results, nighttime sleep duration was categorized as short (<6 h), medium (6-8 h), or long (>8 h), and nap duration was categorized as none (=0 min), short (>0-30 min), or long (>30 min). These categories were combined to construct nine distinct sleep patterns. A multivariate logistic regression model was employed to analyze the joint effects of these sleep patterns on possible sarcopenia. A sensitivity analysis was conducted among older adults with normal total sleep duration to assess the independent association of sleep patterns. Stratified analyses by sex and age were conducted to explore the associations between sleep patterns and possible sarcopenia across different subpopulations.Results The prevalence of possible sarcopenia in the study population was 39.60%. A U-shaped association was observed for both nighttime sleep duration and total sleep duration with possible sarcopenia, while an inverted L-shaped association was found for nap duration. After adjusting for covariates, compared to the reference group with "medium nighttime sleep + short midday nap", individuals with the "short nighttime sleep + no midday nap" pattern exhibited a significantly higher odds of possible sarcopenia (OR = 1.629, 95% CI: 1.302-2.036). Furthermore, the combinations of "short nighttime sleep + long midday nap", "long nighttime sleep + no midday nap", and "long nighttime sleep + long midday nap" were also significantly associated with possible sarcopenia. The sensitivity analysis revealed that the "long nighttime sleep + no midday nap" pattern remained significantly associated with possible sarcopenia (OR = 1.770, 95% CI: 1.191-2.630, P = 0.005) among older adults with normal total sleep duration (6-9 h). Stratified analyses revealed that these adverse associations between specific sleep patterns and possible sarcopenia remained significant among females and individuals aged below 80 years.Conclusion Nighttime sleep duration demonstrated a dominant role within the joint sleep patterns, while the association of napping variability was primarily evident under conditions of non-medium (i.e., either short or long) nighttime sleep duration. Even with normal total sleep duration, the particular sleep structure of "long nighttime sleep without any midday napping" was associated with possible sarcopenia. Overall, a comprehensive assessment of combined nighttime-midday sleep patterns is instrumental in identifying older adults at elevated risk associated with sarcopenia.