title: Insomnia as a risk for depression: a longitudinal epidemiologic study on a Japanese rural cohort.
abstract: OBJECTIVE
  To determine (1) whether insomnia is a factor related to the presence or persistence of depression for 2 years in the Japanese population and (2) which component of insomnia is associated with the presence of depression for 2 years in a rural cohort.
  
  
  METHODS
  This is a community-based longitudinal study. Two thousand eight hundred twenty-five people aged 20 years or older were evaluated at baseline, and of those participants, 1,577 (56%) were reevaluated after 2 years. During both surveys, the participants were asked to describe demographic variables and to fill out self-rating scales of insomnia (Pittsburgh Sleep Quality Index [PSQI]) and depressive symptoms (Center for Epidemiologic Studies Depression Scale).
  
  
  RESULTS
  The results of a multiple logistic regression analysis showed that depression (OR = 6.0; 95% CI, 4.4-8.0) and insomnia (OR = 2.1; 95% CI, 1.5-2.8) at baseline were significantly associated with the presence of depression at the follow-up. Most of the PSQI subscales, except for sleep duration and habitual sleep efficiency, were significantly associated (P < .01) with the presence of depression at the follow-up. In addition, the new appearance and repeated existence of depression at the follow-up were related to persistent insomnia (adjusted ORs = 7.0 and 3.3 [P < .001], respectively). A result of the receiver operating characteristic curve showed that persons with insomnia whose PSQI scores exceeded 8 points at the baseline were most likely to still have insomnia at the follow-up (cutoff point = 7.5).
  
  
  CONCLUSIONS
  On the basis of our results in a Japanese population, insomnia with high severity level could be a risk factor for the presence/persistence of depression in the long-term prognosis.
authors: Japan Somnology Center, Neuropsychiatric Research Institute, Tokyo, Japan.
authors: Isa
authors: I
authors: Okajima
authors: Yoko
authors: Y
authors: Komada
authors: Takashi
authors: T
authors: Nomura
authors: Kenji
authors: K
authors: Nakashima
authors: Yuichi
authors: Y
authors: Inoue
mesh_terms: D000328:Adult; D003863:Depression / Q000150:complications / Q000453:epidemiology*; D005260:Female; D006306:Health Surveys / Q000706:statistics & numerical data; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D012307:Risk Factors; D012424:Rural Population / Q000706:statistics & numerical data*; D057566:Self Report; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications / Q000453:epidemiology*