The association between depression and mortality - a comparison of survey- and register-based measures of depression.

BACKGROUND: A number of studies have associated depression with a high mortality risk. However, in surveys, depression is often measured by self-reports in selected sub-samples, while register studies have been based on hospital diagnosis or purchase of antidepressants. We examined how different survey- and register-based measures of depression were associated with 7-year mortality in a cohort of middle-aged Danish men.

METHODS: The study was based on 10,517 men born in 1953. Depression was assessed through hospital diagnosis for the period from 1969 to 2004 and by self-reported information on depression, use of antidepressants and the Major Depression Inventory (MDI) from a survey in 2004, in which 58.8% (n=6292) of the men participated. Information on mortality and cause of death was retrieved from registers for the period between 2004 and 2011.

RESULTS: Depression diagnosis from hospital registers as well as self-reported depression, use of antidepressants and having a high MDI-score were significantly associated with mortality from all, natural and unnatural causes. The associations were of a similar magnitude for the register-based measure of depression and for the survey-based measures reflecting past depression, but the strongest association was found for current depression as assessed by the MDI-score.

LIMITATIONS: The study population consists almost exclusively of white men and the findings may not be generalizable to female populations or other races and ethnicities.

CONCLUSIONS: Physicians should be aware of male patients with a history of depression from hospital records or self-reported as they have higher mortality risk years after their first symptom.