The Epidemiology of Late Life Depression

The scientific investigation of late life depression cannot be limited to the practitioner's office or the laboratory. Though every clinician treating older persons is exposed to patients with dysphoric symptoms, depressive disorders are manifested unevenly in populations and through time. Clinicians, however, treat patients, not places or populations. Disease appears as a window in time and is rarely conceived of longitudinally. To complete the clinical picture and natural history of depression, the disorder must be studied in the population.' Every clinician is exposed superficially to epidemiology, the study of diseases in populations. In this paper I will attempt to demonstrate the value of epidemiology in the clinical diagnosis and management of depression in late life. Depression is not only a frequent symptom presented by the elderly patient but the clinical manifestation of a major public health problem. As can be seen in Figure 1, the rate of successful suicide increases dramatically with increasing age.' Most suicides are the result of severe depressive episodes. The increase associated with age is due primarily to an increased rate among white men. Yet, this rather dramatic increase with age may go unnoticed, for most suicide attempts occur at earlier stages of the life cycle? Older persons are therefore less likely to attempt suicide but are more likely to be successful in their attempts. Epidemiologic data suggest that a suicide attempt by an older person is usually an earnest attempt, one that must be seriously considered by the clinician. Morris described the domain of epidemiology as a series of tasks to be accomplished before the clinical picture of a disease is completed.' These tasks are listed in Table 1 and are especially applicable to chronic disorders, such as late life depression. To illustrate both their value and their methodologic limitations; three of these tasks will be reviewed: the identification of cases of depression, the distribution of depressive disorders in the population, and historical trends in the prevalence and distribution of depression in the population.