title: Interaction of depressive and anxiety symptoms on the mortality of patients with COPD: a preliminary study.
abstract: BACKGROUND
  Depressive and anxiety symptoms increase the risk of death in patients with Chronic Obstructive Pulmonary Disease (COPD), but the combined effects of the two factors are unknown.
  
  
  OBJECTIVE
  To assess the possible interactive effects of depressive and anxiety symptoms on the death of patients with COPD.
  
  
  METHODS
  Prospective data for 7787 Chinese patients with COPD was analyzed and the deaths were recorded. Depressive and anxiety symptoms were evaluated using the Hospital Anxiety and Depression Scale. A product of depressive and anxiety symptoms was added to the logistic regression model to evaluate the multiplicative interaction, and relative excess risk of interaction (RERI), attributable proportion (AP) of interaction, and synergy index (S) were applied to evaluate the additive interaction of the two factors. Bootstrap was used to calculate 95% confidence intervals (CIs) of RERI, AP and S. RERI > 0, AP > 0, or S > 1 indicated biological interaction.
  
  
  RESULTS
  After 4 years' follow-up, the cumulative mortality was 20.0%, and the percentages of deaths in patients with depressive and anxiety symptoms were 28.5% and 30.9%, respectively. When adjusting for variables such as age, sex, disease duration, marital status, income, education level, co-morbidity, smoke status, biomass smoke, 6MWD, MRC, BMI and FEV1. the RERI, AP, and S (with 95% CIs) resulted in depression and anxiety scores of 6.54 (1.23-13.79), 0.54 (0.18-0.83), and 2.64 (1.33-4.75) respectively.
  
  
  CONCLUSIONS
  Interaction effects were found between depressive and anxiety symptoms on the death of patients with COPD. Patients with both depressive and anxiety symptoms have an increased risk of death from COPD.
authors.affiliation: 1Department of Control and Prevention of Chronic Non-Communicable Diseases, Xuzhou Center for Disease Control and Prevention , Xuzhou, Jiangsu Province, Xuzhou , China.
authors.forename: Peian
authors.initials: P
authors.lastname: Lou
authors.forename: Yanan
authors.initials: Y
authors.lastname: Zhu
authors.forename: Peipei
authors.initials: P
authors.lastname: Chen
authors.forename: Pan
authors.initials: P
authors.lastname: Zhang
authors.forename: Jiaxi
authors.initials: J
authors.lastname: Yu
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.forename: Na
authors.initials: N
authors.lastname: Chen
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Hongmin
authors.initials: H
authors.lastname: Wu
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000368:Aged; D001007:Anxiety / Q000150:complications / Q000453:epidemiology*; D002681:China / Q000453:epidemiology; D003863:Depression / Q000150:complications / Q000453:epidemiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality* / Q000523:psychology*
keywords: anxiety symptoms; death; depressive symptoms; interaction