Lee TA (Hines COE), Sohn MW
(Hines COE), Valenstein M
(Ann Arbor COE), Weiss KB
While chronic conditions are often described and studied in isolation, there is increasing evidence that these chronic conditions and their treatments have complex interrelationships. Depression is a common comorbidity among veterans, and the objective of this study was to assess the impact of a comorbid depression diagnosis on mortality for common groups of multiple chronic conditions.
We identified all veterans ages 45 and older with a diagnosis of arthritis, cancer, dementia, diabetes, hypertension, ischemic heart disease (IHD), respiratory disease, or stroke during fiscal year 2000. Clusters of mutually exclusive combinations of these diseases were created. We determined the 5-year, age-adjusted, all-cause mortality rate for each cluster, and then estimated the relative risk of mortality when depression was added to each cluster.
Among 531,656 veterans, mortality rates were generally higher for persons with more than one chronic condition. The presence of depression was associated with higher mortality risk for most disease clusters. Patients with hypertension, diabetes, and arthritis had a relative mortality risk of 1.43 (95% CI = 1.24, 1.66) compared to patients with those 3 conditions but no depression. Other illness clusters that included hypertension, diabetes, arthritis, and/or IHD had at least a 30% higher mortality risk associated with depression. Depression had a significant protective effect on mortality for patients with hypertension and dementia (RR=0.75, 95% CI = 0.66, 0.85).
There is a noteworthy relationship between depression and higher mortality rates among persons with clusters of common chronic conditions. Further research is needed to explore whether this relationship is causal and the extent to which depression treatment mitigates mortality outcomes among these complex patients.
These findings point to the value of screening veterans with common chronic conditions for depressive symptoms. Given the relationship between depression and mortality in these patients, early and accurate identification of depression may lead to longer life spans for these patients.