title: Difficulty in resuming or inability to resume sleep and the links to daytime impairment: definition, prevalence and comorbidity.
abstract: OBJECTIVE
  To assess the chronicity and severity of nocturnal awakenings with difficulty resuming sleep (DRS), its value as an indicator of an ongoing sleep and/or mental disorder and, finally, how it affects on daytime functioning.
  
  
  METHODS
  A cross-sectional telephone study was performed in the non-institutionalized general population of France, the United Kingdom, Germany, Italy and Spain. This representative sample of 22,740 non-institutionalized individuals aged 15 or over was interviewed on their sleeping habits, health, sleep and mental disorders. These five European countries totaled 245.1 million inhabitants. The evaluation of nocturnal awakenings with DRS included duration, frequency (per night, per week and in the previous months) and assessment scale of daytime functioning. DRS was defined as a complaint of difficulty in resuming or inability to resume sleep occurring at least three nights per week and lasting for at least one month.
  
  
  RESULTS
  A total of 16.1% [95% CI: 15.6-16.6] of the sample had DRS. Prevalence was higher in women and increased with age. The average duration of DRS was 40 months. DRS individuals slept on average 30 min less than other subjects with insomnia symptoms and 60 min less than the rest of the sample. Painful physical conditions, anxiety and mood disorders were the most discriminative factors for individuals with DRS distinguishing them from other insomnia subjects and the rest of the sample. Daytime impairment was observed in 52.2% of DRS individuals compared to 32.8% in individuals with classical insomnia symptoms (p < 0.0001).
  
  
  CONCLUSIONS
  (1) DRS affect a large segment of the population; (2) it is a good indicator of an ongoing sleep or mental disorder; (3) it has a stronger impact on daytime functioning than classical insomnia symptoms (OR: 4.7).
authors.affiliation: Stanford Sleep Epidemiology Research Center, Stanford University School of Medicine, 3430 W. Bayshore Road, Palo Alto, CA 94303, USA. mohayon@stanford.edu
authors.forename: Maurice M
authors.initials: MM
authors.lastname: Ohayon
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003072:Cognition Disorders / Q000453:epidemiology; D015897:Comorbidity; D003430:Cross-Sectional Studies; D006970:Disorders of Excessive Somnolence / Q000453:epidemiology* / Q000628:therapy; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007391:International Cooperation; D008019:Life Style; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology; D008875:Middle Aged; D016017:Odds Ratio; D015995:Prevalence; D007319:Sleep Initiation and Maintenance Disorders / Q000145:classification / Q000453:epidemiology* / Q000628:therapy; D055815:Young Adult