Validation of Sleep Pattern and Intrinsic Capacity in Older Adults: A Longitudinal Chinese Study Assessing Healthy Ageing

Background: Intrinsic capacity (IC) has been established in the ageing framework by the World Health Organization to address the challenges of population ageing. However, the detailed relationship between this novel assessment and sleep pattern remains inadequately elucidated.Methods: This prospective nationwide cohort study examined the relationship between self-reported sleep information and IC change including 16,070 participants. 29 covariates were adjusted for, demographic characteristics, lifestyle, and health conditions. We applied linear regression, regression splines, Mendelian randomization (MR), subgroup/sensitivity analyses, and mediation analysis to examine the linear and nonlinear, causal and generalizability, heterogeneous, and mediated effects of sleep pattern on IC change.Findings: Both excessive (>10 hours) and insufficient (<6 hours) sleep duration were significantly associated with an accelerated decline with IC change (P <0.01). And nap duration of ≤60 minutes was found to have an optimal level of IC change. The IC change and sleep pattern showed an inverted J-shaped (non-linear P <0.01). IC values decreased at the slowest rate when nap time constituted one-seventh of total sleep time. Two-sample MR estimates demonstrated causal effects of sleep pattern on the IC change (P <0.001). Dyslipidemia onsets partially mediated the association between naps (≤ 60 minutes) and IC change (P = 0.02).Interpretation: Maintaining the sleep pattern of 6-8 hours of night or total sleep, along with daytime nap duration ≤60 minutes help preserve optimal IC change or delay IC decline in middle-aged and older adults. This specific sleep pattern serves to actively facilitate the healthy process of ageing.Funding: This study was supported by a grant from the National Science Foundation of China (No. 82374406), the Young Elite Scientists Sponsorship Program by CAST (CACM-2021-QNRC2-B30), Natural Science Foundation of Guangdong Province/Guangzhou City (2021A1515011457 and 2023A1515030146) and Guangzhou Science and Technology Project (202206080015), and Guangzhou University of Chinese Medicine's Youth Elite Talents Cultivation "List Unveiling and Leadership" Team Project. Excellent Doctoral Dissertation Cultivation Project of the First Clinical School of Guangzhou University of Traditional Chinese Medicine in 2023 (YB202301).Declaration of Interest: The authors declare no conflicts of interest.Ethical Approval: The CHARLS survey, which we utilized in our study, received approval from the Ethical Review Committee of Peking University (approval number IRB00001052–11015). The study data were anonymized, and all participants provided signed informed consent during their participation. Approved data users were not required to seek additional ethics approval.