title: Habitual sleep patterns and the distribution of body mass index: cross-sectional findings among Swedish men and women.
abstract: OBJECTIVE
  To compare distributions of body mass index (BMI) between individuals with different habitual sleep patterns.
  
  
  METHODS
  We performed cross-sectional analyses of 40,197 Swedish adults (64% women), who reported sleep duration and quality, weight, height, and possible confounding factors in 1997. Using quantile regression, we estimated associations between sleep patterns and selected percentiles of the distribution of BMI.
  
  
  RESULTS
  While the medians were similar, larger adjusted values of BMI were estimated in the upper part of the distribution among men and women with short sleep (≤5 h) compared with medium-length sleep (6-8 h). For example, in men, the 90th percentile of BMI was 0.80 kg/m(2) (95% confidence interval: 0.17-1.43 kg/m(2)) higher among short sleepers. In women, long sleepers (≥9 h) also showed larger values in the upper part of the BMI distribution; the 90th percentile was 1.23 kg/m(2) (0.42-2.04 kg/m(2)) higher than in medium-length sleepers. In male long sleepers, smaller values were estimated in the lower part of the BMI distribution; the 10th percentile was 0.84 kg/m(2) lower (0.35-1.32 kg/m(2)) than in medium-length sleepers. The 90th percentile of BMI in women with poor-quality compared with good-quality sleep was larger by 0.82 kg/m(2) (0.47-1.16 kg/m(2)); the 10th percentile was smaller by 0.17 kg/m(2) (0.02-0.32 kg/m(2)).
  
  
  CONCLUSIONS
  Short, long or poor-quality sleepers showed larger, or smaller, values at the tails of the BMI distribution, but similar medians. Hence, unfavorable sleep patterns and BMI were associated only in a subset of this study population.
authors.affiliation: Unit of Clinical Epidemiology, Department of Medicine, Karolinska Institutet, Stockholm, Sweden. Electronic address: anna.k.westerlund@ki.se.
authors.forename: Anna
authors.initials: A
authors.lastname: Westerlund
authors.affiliation: Division of Biostatistics, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Matteo
authors.initials: M
authors.lastname: Bottai
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA; Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Hans-Olov
authors.initials: HO
authors.lastname: Adami
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; Department of Statistics and Quantitative Methods, University of Milano-Bicocca, Milan, Italy.
authors.forename: Rino
authors.initials: R
authors.lastname: Bellocco
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Olof
authors.initials: O
authors.lastname: Nyrén
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, Sweden; Division of Psychology, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Åkerstedt
authors.affiliation: Unit of Clinical Epidemiology, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Ylva Trolle
authors.initials: YT
authors.lastname: Lagerros
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology; D050177:Overweight / Q000453:epidemiology; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000453:epidemiology / Q000503:physiopathology; D012893:Sleep Wake Disorders / Q000453:epidemiology / Q000503:physiopathology; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors
keywords: Body mass index; Epidemiology; Gender; Quantile regression; Sleep duration; Sleep quality