title: Workaholism and sleep quality among Japanese employees: a prospective cohort study.
abstract: BACKGROUND
  This study focused on workaholism as a personal attitude toward work and examined its effects on sleep quality among Japanese employees from various occupations.
  
  
  OBJECTIVE
  The present study aimed to demonstrate the prospective association of workaholism (i.e., working excessively hard in a compulsive fashion) with sleep quality among Japanese employees.
  
  
  METHODS
  A Web-based prospective survey was conducted in October 2010 and May 2011 among registered monitors of a survey company. The questionnaire included workaholism, sleep quality, job characteristics, and demographics. Overall, 13,564 monitors were randomly invited to complete the first wave of the survey. The first 2,520 respondents were included in this study. The respondents who completed the first wave were invited to complete the second wave of the survey; 2,061 answered. A total of 364 respondents who changed their working conditions during the follow-up period were excluded. In addition, due to missing values, data from 14 respondents were excluded. Thus, the responses from 1,683 respondents were included in the analysis (859 males and 824 females). An analysis of covariance (ANCOVA) was conducted to compare adjusted sleep quality at follow-up among workaholism groups (low, middle, and high). To conduct the ANCOVA, we adjusted for demographics, sleep quality at baseline, and job characteristics.
  
  
  RESULTS
  The high-workaholic group had significantly longer sleep latency at follow-up compared with the low- and middle-workaholic groups after adjusting for demographics, sleep latency at baseline, and job characteristics. In addition, the high-workaholic group demonstrated significantly higher levels of daytime dysfunction compared with the low-workaholic group. However, no significant differences were found among workaholic groups in terms of overall sleep quality, sleep duration, habitual sleep efficiency, sleep disturbance, and use of sleep medication.
  
  
  CONCLUSIONS
  Workaholism was associated with poor sleep quality at the 7-month follow-up in terms of sleep latency and daytime dysfunction.
authors.affiliation: Department of Mental Health, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, tothankyouall@gmail.com.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Kubota
authors.forename: Akihito
authors.initials: A
authors.lastname: Shimazu
authors.forename: Norito
authors.initials: N
authors.lastname: Kawakami
authors.forename: Masaya
authors.initials: M
authors.lastname: Takahashi
mesh_terms: D000223:Adaptation, Psychological; D000328:Adult; D000704:Analysis of Variance; D003193:Compulsive Personality Disorder / Q000503:physiopathology / Q000523:psychology*; D005260:Female; D006306:Health Surveys; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D009790:Occupations; D011446:Prospective Studies; D012890:Sleep / Q000502:physiology*; D007319:Sleep Initiation and Maintenance Disorders / Q000209:etiology* / Q000503:physiopathology; D011795:Surveys and Questionnaires; D014940:Work Schedule Tolerance / Q000502:physiology / Q000523:psychology*