Associations of daytime napping and nighttime sleep with multimorbidity progression trajectories in middle-aged and older chinese adults.

Aim: Both nighttime sleep and daytime napping behaviors have been linked to various individual diseases. This study aimed to explore their independent and combined effects on multimorbidity progression in Chinese middle-aged and older adults.

Methods: We included 6517 participants aged ≥45 from the China Health and Retirement Longitudinal Study (2011-2015). Self-reported sleep and napping durations were investigated in 2011. Multimorbidity was assessed based on 14 chronic diseases, and progression trajectories were identified by tracking number of chronic diseases. Logistic regression was used with normal sleep and no napping as the reference.

Results: Three trajectories were identified: no, slow, and rapid progression. Both short napping (vs. slow, OR = 1.361, 95 % CI = 1.111-1.698) and short sleep (vs. no, OR = 1.877, 95 % CI = 1.485-2.373) increased rapid progression risk. Short sleep also increased slow progression risk (vs. no, OR = 1.414, 95 % CI = 1.182-1.691), while short napping did not. Long sleep and medium/long napping showed no significant associations. In stratified analyses, short napping effects were limited to females and older participants. However, short sleep effects were found in all subgroups except for rapid vs. slow among older adults. Short sleep and short napping exhibited a synergistic effect on rapid progression (vs. no, OR = 4.108, 95 % CI = 2.463-6.853); normal sleep plus any napping was not associated with risk.

Conclusion: Short sleep and short napping independently and jointly contribute to multimorbidity progression. Conversely, normal sleep plus any napping was not associated with progression risk.