title: Association between number of comorbid conditions, depression, and sleep quality using the Pittsburgh Sleep Quality Index: results from a population-based survey.
abstract: OBJECTIVE
  Although sleep problems are a serious public concern, it is not clear if the presence of depression or multiple comorbid conditions has an additive or multiplicative effect on sleep quality.
  
  
  METHODS
  We conducted a population-based, cross-sectional survey in a rural town in Japan. Multivariable-adjusted linear regression models were used to explore the association between the number of comorbid conditions and the Pittsburgh Sleep Quality Index (PSQI) global score. The association between the number of comorbid conditions and presence of depression, as defined by the five-item Mental Health Inventory (scores60), in those with poor quality sleep (PSQI global score>5) was determined using a non-parametric trend test.
  
  
  RESULTS
  Of 5107 respondents, 3403 (mean age: 51.0years, women: 52.6%) were used for the analysis after exclusion of missing PSQI data. The PSQI global score (mean: 4.9) increased as the number of comorbid conditions increased in a linear and statistically significant manner (p<0.0001). The PSQI global score increased by 0.374 for each additional comorbid condition (p<0.0001). Among those with poor sleep quality, the proportion with depression increased significantly and linearly (p<0.0001) as the number of comorbid conditions increased (37.5% for 0 vs. 59.9% for 4 comorbid conditions).
  
  
  CONCLUSIONS
  The number of comorbid conditions correlated positively with poor sleep quality, and as the number of comorbid conditions increased, the proportion of those also suffering from depression increased. Recognizing the signs of depression in patients with multiple comorbid conditions is important because of its exacerbation of poor sleep quality.
authors.affiliation: Department of Epidemiology and Healthcare Research, Kyoto University Graduate School of Medicine, Japan. hayasino-y@umin.net
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Hayashino
authors.forename: Shin
authors.initials: S
authors.lastname: Yamazaki
authors.forename: Misa
authors.initials: M
authors.lastname: Takegami
authors.forename: Takeo
authors.initials: T
authors.lastname: Nakayama
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sokejima
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuhara
mesh_terms: D021081:Chronobiology Disorders / Q000175:diagnosis / Q000453:epidemiology; D015897:Comorbidity; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance / Q000379:methods; D012893:Sleep Wake Disorders / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*; D011795:Surveys and Questionnaires
chemical_list: D006993:Hypnotics and Sedatives