Abstract
BACKGROUND: Education and living environment are related to mental health. But the independent and combined effects of them on mental health among patients with chronic obstructive pulmonary disease (COPD) are uncertain. METHODS: The independent and combined effects of education and living environment on mental health were assessed by binary logistic regression in 1064 COPD patients. Additive interaction was assessed with the relative excess risk ratio (RERI), attribution percentage (AP), and synergy index (SI). RESULTS: Our results shown that low education level and urban living environment were independently associated with higher risks for anxiety (odds ratio [OR]: 1.56, 95% confidence interval [CI] 1.06-2.29 and OR:2.15, 95% CI 1.51-2.05) or depression (OR:1.62, 95% CI 1.17-2.27 and OR: 2.01, 95% CI 1.46-2.75) among COPD patients. The combination effect of them was also associated with higher risks for anxiety (OR: 7.90, 95% CI 3.83-16.29, P < 0.001) or depression (OR: 11.79, 95% CI 5.77-24.10, P < 0.001) among these patients. Furthermore, we observed strong synergistic additive interactions between them for anxiety (SI: 11.57, 95% CI 1.41-95.27; RERI: 6.31, 95% CI 1.60-11.01; AP: 0.8, 95% CI 0.66-0.94) and depression (SI: 31.31, 95% CI 1.59-617.04; RERI: 10.44, 95% CI 2.66-18.23; AP: 0.89, 95% CI 0.8-0.97). CONCLUSION: Low education levels and living in urban areas had an independent and synergistic effects on mental health among COPD patients.