Villejuif, France - A large case-control study has shown a link between clinical depression and out-of-hospital cardiac arrest (CA) that was independent of established coronary heart disease risk factors [1]. Dr Jean-Philippe Empana (Sudden Death Epidemiology Unit, Hôpital Paul Brousse, Villejuif, France) and colleagues report their findings in the January 23, 2006 issue of Archives of Internal Medicine.

"Our study shows there is something, a relationship between depression and sudden death," Empana told heartwire. The results extend the observations of two previous studies that have shown a link between depression and cardiac death, he says, adding that these were limited to specific populations—those who had already had an MI in one case and those aged over 70 in the other.

"Furthermore, our findings suggest a dose effect, whereby the risk of out-of-hospital cardiac arrest increases with increasing severity of depression, which has not previously been investigated."

Empana, working with scientists in Seattle, used data from a population-based case-control study of risk factors for incident out-of-hospital cardiac arrest conducted among enrollees of an HMO in western Washington State. Cases (n=2228) were aged 40 to 79 years and had a cardiac arrest between 1980 and 1994; these were compared with 4164 controls. Clinical depression was defined as physician diagnosis of depression or use of antidepressant treatment within the year before the event. Referral to mental-health clinics or hospitalization for depression defined severe depression.

Clinically depressed patients had a higher odds ratio of cardiac arrest (1.88), which persisted (and remained highly significant) after adjustment for confounders, including smoking, heavy drinking, hypertension, diabetes, and history of MI and CHF (OR 1.43).

The association was seen in both sexes, in various age groups, and in subjects with prior physician-diagnosed heart disease (OR 1.27) as well as those without prior physician-diagnosed heart disease (OR 1.71). Compared with nondepressed subjects, the risk of cardiac arrest was increased in less severely depressed people (OR 1.30) and further increased in those with severe depression (OR 1.77).

The fact that the odds ratio was decreased after adjusting for major CHD risk factors suggests that atherosclerosis may in part be implicated in the link between depression and cardiac arrest, say the researchers, but other mechanisms are obviously at play too, as the association remained after adjustment.

"These results may have potential clinical implications with regard to risk stratification for out-of-hospital cardiac arrest," they conclude.