Depression is a common mental illness among middle-aged and elderly people. However, few studies have explored the relationship between smoke exposure and depression in those aged ≥ 45 years. This study aims to determine the association between the level of smoke exposure and depression in middle-aged and elderly individuals. We extracted the data from the National Health and Nutrition Examination Survey (NHANES) 2005–2018, focusing on U.S. participants aged 45 years or older with complete data. Depression was assessed using the Patient Health Questionnaire-9 (PHQ-9), based on Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria. Combusted cigarette smoke exposure was defined in three ways: self-reported smoking status, serum cotinine level, and a composite indicator combining self-reported smoking status, serum cotinine level, use of nicotine-containing products in the last five days, and household smokers. Three multivariable binary logistic regression models (Models 1–3) were established based on the three definitions of smoke exposure, and restricted cubic spline (RCS) analysis was used. This study included 9,571 participants aged ≥ 45 years, with 747 (7.80%) showing depressive symptoms. Model 1 indicated that current smokers were more likely to experience depression (compared to non-smokers, current smokers: OR of being depressed = 2.03 95% CI : 1.65 ~ 2.49, P 3.08 ng/ml were at increased risk for depression (compared to serum cotinine level 3.08 ng/ml: OR = 1.99 95% CI : 1.63 ~ 2.43, P < 0.001). In Model 3, active smokers were more prone to depression (compared to no smoke exposers, active smokers: OR = 2.26 95% CI : 1.80 ~ 2.84, P < 0.001). The RCS regression revealed that serum cotinine level and depression showed a linear relationship. In the U.S. population aged 45 and older, higher levels of smoke exposure were associated with an increased risk of depression. Increasing public attention and caring for mental health of middle-aged and elderly individuals, especially females, and reducing exposure to smoke will minimize the incidence of depression.
Wang et al. (Fri,) studied this question.