Abstract
BACKGROUND: Dose-response and nonlinear relationships of cigarette exposure with sleep disturbances and depression are warranted, and the potential mechanism of sex hormones in such associations remains unclear. METHODS: Cigarette exposure, trouble sleeping, and depression were assessed by standard questionnaires, and the levels of cotinine and sex steroid hormones were determined among 9900 adults from the National Health and Nutrition Examination Survey (NHANES). Multiple linear regression, logistic regression, and mediation models were conducted to evaluate the associations between smoking, sex steroid hormones, trouble sleeping, and depression. RESULTS: With never smokers as a reference, current smokers had a higher prevalence of trouble sleeping (OR = 1.931, 95% CI: 1.680, 2.219) and depression (OR = 2.525, 95% CI: 1.936, 3.293) as well as testosterone level (β = 0.083, 95% CI: 0.028, 0.140). Pack-years of smoking and cigarettes per day were positively associated with the prevalence of trouble sleeping and depression as well as testosterone level (P(trend) <0.05). The restricted cubic spline model showed linear relationships of cotinine with trouble sleeping, depression, and testosterone. The positive associations of cigarettes per day with trouble sleeping and depression were greater in females than that in males (P(modification) <0.05). However, the potential role of sex hormones was not observed in the association of cotinine with trouble sleeping or depression (P(mediation) >0.05). CONCLUSION: Smoking may induce sex hormone disturbance and increase the risk of sleep problems and depression symptoms, and ceasing smoking may reduce the risk of such complications.