Distinct trajectories of 24-hour sleep duration and subsequent functional limitations in older adults: a national longitudinal cohort study

Static sleep duration is a known health determinant, yet the prognostic value of longitudinal 24-hour sleep trajectories for functional deterioration remains understudied. However, whether longitudinal 24-hour sleep trajectories are associated with subsequent overall and severe functional limitations remains unclear. We analysed 4,999 adults aged ≥ 50 years from the China Health and Retirement Longitudinal Study (CHARLS), free of baseline functional limitations. Latent class mixed models identified distinct 24-hour sleep duration trajectories over 4 years. We estimated risk ratios (RRs) for ADL and IADL limitations at Wave 5, as well as severe limitations defined as difficulty in two or more tasks. Three trajectories were identified: Stable Moderate (56.5%), Progressively Short (13.5%; ~5.1 h to ~ 3.9 h), and Progressively Long (30.0%; ~8.4 h to ~ 9.2 h). Compared with the Stable Moderate group, the Progressively Short trajectory was associated with higher risks of ADL limitation (RR = 1.34; 95% CI: 1.18–1.52) and IADL limitation (RR = 1.22; 95% CI: 1.08–1.37) at Wave 5, as well as severe ADL limitation. Conversely, the Progressively Long trajectory was not associated with overall ADL or IADL limitations at Wave 5, but was associated with severe ADL and IADL limitations. Longitudinal changes in 24-hour sleep duration were associated with subsequent functional limitations in older adults. Progressively sleep shortening may serve as a marker of functional vulnerability, whereas sleep lengthening may indicate more advanced dependency. These findings support the potential value of sleep trajectories for risk stratification, while causal interpretation requires caution. Longitudinal sleep trajectories were associated with subsequent functional limitations. Progressive shortening of sleep duration was linked to higher risk of ADL and IADL limitations at Wave 5. Progressive lengthening was mainly associated with severe functional limitations. Monitoring sleep changes may help identify older adults at elevated functional risk.