Insomnia, depression, and physical disorders in late life: a 2-year longitudinal community study in Koreans.

STUDY OBJECTIVES: To investigate prevalence, incidence, and persistence of insomnia, and their bidirectional longitudinal associations with depression and physical disorders.

DESIGN: A community based longitudinal study.

SETTING: Elders living in private households in South Korea.

PARTICIPANTS: 1204 people > or = 65 years of age were evaluated at baseline; 909 of them (75%) were re-interviewed after 2 years.

MEASUREMENTS AND RESULTS: Insomnia was defined as difficulty in initiation or maintenance of sleep > or = 3 nights per week over the last month. Diagnosis of depression (Geriatric Mental State) and number of physical disorders were ascertained. Sociodemographic and clinical covariates included age, gender, education, housing, past occupation, current employment, living area, life events, social deficit, physical activity, cognitive impairment, anxiety, and daily drinking. Of those (27%) with insomnia at baseline, 40% had insomnia at follow-up. Of those without insomnia at baseline, 23% had insomnia at follow-up. Baseline depression was significantly associated with prevalence and incidence of insomnia. Baseline number of physical disorders was significantly associated with prevalence, incidence, and persistence of insomnia. Baseline insomnia was independently associated with incident depression and an increase in reported physical disorders.

CONCLUSIONS: Insomnia was common and often persistent in this population. Insomnia was closely and reciprocally related to depression and physical disorders.