Contribution of depressive symptoms to mortality for elderly hypertension patients: Analysis using a national representative longitudinal survey

Background: Previous research suggested that hypertension and depressive symptoms are two of the important causes of mortality for the elderly. However, no existing research has formally tested the interactive effect between hypertension and depressive symptom on mortality for the elderly. Methods: This research used data from the Survey of Health and Living Status of the Middle Age and Elderly (SHLS) conducted by the Taiwan Bureau of Health Promotion. Waves 1989, 1996, 1999, 2003 and 2007 were used. 3,736 respondents aged 60 and above completed the survey at the initial wave. Four groups of subjects were identified: (A) neither hypertension nor depression, (B) no hypertension but depression, (C) hypertension but no depression, (D) both hypertension and depression. The interactive effects of depressive symptoms with hypertension on mortality were estimated using Cox proportional hazard model. Different models were estimated for younger old (<70 years) and older old (>= 70 years). Results: In the full model, the HRs for the no hypertension/depression, hypertension/no depression, and hypertension/depression were 1.11 (95% CI 0.97, 1.27), 1.25 (95% CI 1.13, 1.38), and 1.42 (95% CI 1.19, 1.70), respectively, compare with the reference group of no hypertension/no depressive symptoms. The pattern remained after separating the subjects into younger old and older old. However, a stronger effect was observed for the older cohort. Conclusions: Depressive symptoms contribute significantly to the hypertension- mortality relationship for the elderly. A clear interactive effect was found. For the elderly, hypertension should be tackled along with depressive symptoms for the elderly to reduce mortality associated with hypertension.