Depression, hypertension, and comorbidity: Disentangling their specific effect on disability and cognitive impairment in older subjects

We aimed to demonstrate that depression and hypertension are associated independently of each other with disability and cognitive impairment in older subjects and that such an association is not attributable to number and severity of comorbidities. An observational study was performed on elderly patients admitted to the Hospital Network of the Italian National Research Center on Aging (INRCA) from January 2005 to December 2006. Depression was defined according to 15-item geriatric depression scale (GDS) score; physical disability according to activities of daily living (ADL) and instrumental activities of daily living (IADL) scores; cognitive impairment on the mini-mental state examination (MMSE) test; the number and severity of comorbidities by means of physician-administered cumulative illness rating scale (CIRS). Among 6180 older subjects (age = 79.3 ± 5.8 years; 47% men), 48.3% were normotensive, 21.8% normotensive depressed, 21.7% hypertensive, and 8.2% hypertensive and depressed. Both depression and hypertension remained significantly associated with functional disability and cognitive impairment. When controlling for age, gender, the number and severity of comorbidities, hypertension was associated with a significantly higher likelihood of having functional disability or cognitive impairment only in the presence of depression (odds ratio = OR = 2.02, 95% confidence interval = 95%CI = 1.60-2.54, p< 0.001 for functional disability; OR = 2.21, 95%CI = 1.79-2.74, p< 0.001 for cognitive impairment) as compared to normotensive controls without depression. We conclude that depression per se' or co-occurrence of hypertension and depression is associated with higher functional disability and cognitive impairment in older subjects. This effect is not attributable to the number or to the severity of comorbidities.