Depressive Tendency and the Risk of Death from Pneumonia: The JACC Study.

Objective The burden of death from pneumonia is expected to increase with the aging of the population, as has been observed in Japan. Depressive tendency, a common psychosocial sign, may be a risk factor for pneumonia due to its possible association with some immune dysfunction. This study aimed to clarify the association between depressive tendency and the risk of death from pneumonia. Methods A population-based cohort that consisted of 75,174 Japanese men and women was followed for a median of 19.1 years. Four psychological and behavioral symptoms (depressive symptoms) were used to evaluate depressive tendency. Results A total of 1,329 deaths from pneumonia were observed. Depressive symptoms were positively and dose-dependently associated with the risk of death from pneumonia (p<0.001 for trend), and subjects with ≥2 depressive symptoms showed a significantly elevated risk compared to those without any symptoms [multivariable hazard ratio (HR), 1.66; 95% confidence interval (CI), 1.39-1.99]. This association was not significantly affected by sex or age at baseline. The elevated risk was still significant even when subjects were limited to those without any medical histories. The excess risk was observed not only for death occurring within the first 10 years of follow-up (multivariable HR, 2.05; 95% CI, 1.51-2.78) but also for that occurring in the longer follow-up period (multivariable HR, 1.48; 95% CI, 1.18-1.85). Conclusion Depressive tendency may be a risk factor for death from pneumonia. Further studies using a more reliable tool for the evaluation of depressive state are necessary to confirm this relationship.