Joint effect of sleep patterns and secondhand smoke exposure with mortality among non-smoking adults

Abstract Introduction Unhealthy sleep and secondhand smoke (SHS) exposure are independent risk factors for death. Their joint association with all-cause and cardiovascular disease (CVD) mortality (ACDM) deserves to be investigated in a nationally representative population. Methods Data from 15175 adults from the National Health and Nutrition Examination Survey database (2005–2014) were analyzed. The study endpoints were all-cause and CVD mortality. Sleep patterns (healthy, intermediate, and poor) were classified based on self-reported questionnaires, including sleep duration, self-reported trouble sleeping and doctor-diagnosed sleep disorders. SHS exposure among nonsmokers was defined according to cotinine levels in serum. Multivariate Cox hazards regression models were conducted to assess the association between sleep patterns and SHS exposure, alone and in combination, with ACDM. Results During 15 years of follow-up, 2016 all-cause deaths and 678 CVD deaths were recorded. In multivariable models, poor sleep was independently associated with higher risk of all-cause (hazard ratio [HR] 1.32; 95% confidence interval [CI] 1.15-1.51) and CVD mortality (HR= 1.31; 95% CI: 1.02-1.68). Exposure to SHS was associated with higher risk of all-cause (HR, 1.21; 95% CI, 1.08-1.36) and CVD mortality (HR, 1.25; 95% CI, 1.04-1.50). In the joint analyses, participants with both unhealthy sleep patterns (intermediate and poor) and SHS exposure had a significantly higher risk of all-cause (HR, 1.48; 95% CI: 1.26–1.74) and CVD mortality (HR, 1.51; 95% CI, 1.15–1.97) than those with neither risk factor. Conclusions The coexistence of SHS exposure and unhealthy sleep patterns was associated with an increased risk of death from all causes and CVD. Implications The findings of this study indicate that both poor sleep patterns and exposure to SHS are independently associated with a higher risk of all-cause and CVD mortality. Furthermore, the coexistence of SHS exposure and unhealthy sleep patterns further increases the risk of mortality from all causes and CVD. Since both sleep patterns and SHS exposure are modifiable factors, interventions aimed at reducing SHS exposure and improving sleep quality could have significant implications in reducing these adverse effects and lowering mortality risk.