Introduction

According to the results of this 6-year prospective study recently published in the journal Circulation, symptoms of depression among the elderly are an independent risk factor for coronary heart disease (CHD). Several epidemiological studies have documented a relationship between depression and cardiovascular risk, yet most of these studies are based on data from middle-age individuals. The authors of this study investigated whether symptoms of depression in a healthy elderly cohort put them at higher risk for coronary heart disease and total mortality.

Method

Close to 4,500 elderly Americans (>65 years) enrolled in the multi-center Cardiovascular Health Study were followed for the development of CHD and mortality over a six-year period. The participants, who were free of cardiovascular disease at entry, gave information on their depressive status at baseline and annually for the following six years. Participants' depressive status was assessed using the Depression Scale of the Center for Epidemiological Studies (CES-D). The absence of cardiovascular disease at baseline was confirmed through clinical exam and review of hospital records, or both. A cumulative mean depression score was assessed for each participant up to the time of a cardiac event - angina, myocardial infarction, angioplasty, bypass graft, or coronary death.

A time-dependent, proportional-hazards model was used to calculate an unadjusted score for each 5-unit increase in the cumulative mean depressive score. Using multivariate analysis, scores were adjusted for age, sex, race, education, diabetes, hypertension, cigarette smoking, total cholesterol, triglyceride level, congestive heart failure and physical activity.

Results

The age range of participants at entry to the study was 65 to 98 years, with a mean age of 72 years for women and 73 years for men. Depression was not associated with age at study entry. White women and men comprised 84% and 85% of the study cohort respectively. At study entry, non-whites had higher depressive scores than whites ( 4.9 versus 3.7; p<0.001).

Cumulative Mean Depression Scores and Events:

• Every 5-unit increase in participants' mean cumulative depressive score before an event was associated with a 15% increased risk for developing CHD (unadjusted hazards ratio [HR] 1.15; CI 95%, 1.04-1.26). For mortality, every 5-unit increase was associated with a 29% increased risk for death (unadjusted HR 1.29; CI 95%, 1.18-1.41).
• In multivariate analysis, each 5-unit increase was associated with a 15% increased risk for CHD (adjusted HR 1.15; CI 95%, 1.04-1.27) and a 16% increased risk for death (adjusted HR 1.16; CI 95%, 1.04-1.28).
• The increased risk was shown to hold equally true for both men and women, with no significant differences between the sexes.

For participants with the highest mean cumulative depression scores (15 units or more), the risk of CHD increased by 40% and the risk of dying by 60%, compared to that in participants with the lowest mean cumulative depressive scores (4 units or less).

Baseline CSE-D Scores and Events:
Participants with higher baseline CSE-D scores had a significantly higher risk of dying (p=0.004), although the risk for CHD was non-significant (p=0.162). However, after adjustment for demographic and cardiovascular risk factors, the baseline depression score was a significant predictor of CHD (p=0.032) and mortality (p=0.012).

Conclusions

This study shows that depressive symptoms are an independent risk factor for the development of CHD and total mortality among elderly Americans. These results are consistent with other studies, which demonstrate that depression constitutes a risk for cardiovascular disease. This study is significant because it focuses exclusively on the elderly, provides a large amount of prospective data, and demonstrates the incremental risks of CHD associated with increasing depression scores.

A recent study showed that elderly patients accrue 50% higher medical care costs than non-depressed elderly.¹Increased awareness and early screening may help reduce health care costs and the suffering associated with depression. The authors note that most physicians under-recognize depressive symptoms in elderly patients, which leads to the elderly being under-diagnosed and under-treated.