Composite sleep patterns and the allergy-related composite outcome among American and Chinese older adults: exploration of depressive symptoms as a potential mediator

BACKGROUND: Sleep disturbances and depressive symptoms commonly co-occur in older adults, but their associations with heterogeneous allergy-related outcomes and the role of depressive symptoms remain unclear. METHODS: We analyzed 1,562 participants aged ≥60 years from NHANES 2005-2006. A composite sleep pattern combined sleep duration, trouble sleeping, and diagnosed sleep disorders. The allergy-related composite outcome comprised elevated total immunoglobulin E and seven questionnaire-assessed disease or symptom outcomes. Survey-weighted logistic regression evaluated associations. Depressive symptoms were assessed with a modified 8-item Patient Health Questionnaire (PHQ-8), and statistical mediation examined indirect associations through its continuous score. We also conducted a complementary longitudinal analysis in 6,146 Chinese older adults from CHARLS. RESULTS: Poor versus healthy sleep was associated with higher odds of the allergy-related composite outcome (OR 2.100; 95% CI 1.328-3.322), wheeze (OR 2.148; 95% CI 1.296-3.559), and sneeze (OR 1.636; 95% CI 1.135-2.357). The estimated indirect association through depressive symptoms represented 22.5% of the total association. In CHARLS, impaired sleep quality was associated with incident asthma (OR 1.689; 95% CI 1.254-2.275), and the corresponding indirect association through depressive symptoms represented 28.3% of the total association. CONCLUSION: Poor sleep was associated with heterogeneous allergy-related outcomes among US older adults, while CHARLS provided complementary longitudinal evidence for incident asthma. Depressive symptoms statistically accounted for part of the observed sleep-allergy association.