title: The association of body size in early to mid-life with adult urinary 6-sulfatoxymelatonin levels among night shift health care workers.
abstract: BACKGROUND
  Adult body mass index (BMI) has been associated with urinary melatonin levels in humans; however, whether earlier-life body size is associated with melatonin, particularly among night shift workers, remains unknown.
  
  
  METHODS
  We evaluated associations of birth weight, body shape (or somatotype) at ages 5 and 10, BMI at age 18 and adulthood, weight change since age 18, waist circumference, waist to hip ratio, and height with creatinine-adjusted morning urinary melatonin (6-sulfatoxymelatonin, aMT6s) levels among 1,343 healthy women (aged 32-53 at urine collection, 1996-1999) in the Nurses' Health Study (NHS) II cohort. Using multivariable linear regression, we computed least-square mean aMT6s levels across categories of body size, and evaluated whether these associations were modified by night shift work.
  
  
  RESULTS
  Adult BMI was inversely associated with aMT6s levels (mean aMT6s levels = 34 vs. 50 ng/mg creatinine, comparing adult BMI ≥ 30 vs. <20 kg/m(2); P trend < 0.0001); however, other measures of body size were not related to aMT6s levels after accounting for adult BMI. Night shifts worked prior to urine collection, whether recent or cumulatively over time, did not modify the association between adult BMI and aMT6s levels (e.g., P interaction = 0.72 for night shifts worked within two weeks of urine collection).
  
  
  CONCLUSIONS
  Our results suggest that adult BMI, but not earlier measures of body size, is associated with urinary aMT6s levels in adulthood. These observations did not vary by night shift work status, and suggest that adult BMI may be an important mechanism by which melatonin levels are altered and subsequently influence chronic disease risk.
authors.affiliation: Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 181 Longwood Avenue, Boston, MA, 02115, USA. cor080@mail.harvard.edu.
authors.forename: Cody A
authors.initials: CA
authors.lastname: Ramin
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston, MA, USA. jmassa@hsph.harvard.edu.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Massa
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA. LRW@mail.harvard.edu.
authors.forename: Lani R
authors.initials: LR
authors.lastname: Wegrzyn
authors.affiliation: Division of Biostatistics and Epidemiology, University of Massachusetts, Amherst, MA, USA. snboyer@schoolph.umass.edu.
authors.forename: Susan B
authors.initials: SB
authors.lastname: Brown
authors.affiliation: Massachusetts College of Pharmacy and Health Sciences, Boston, MA, USA. jeffrey.pierrepaul@my.mcphs.edu.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Pierre-Paul
authors.affiliation: Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 181 Longwood Avenue, Boston, MA, 02115, USA. nheed@channing.harvard.edu.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Devore
authors.affiliation: Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 181 Longwood Avenue, Boston, MA, 02115, USA. shankinson@schoolph.umass.edu.|Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA. shankinson@schoolph.umass.edu.|Division of Biostatistics and Epidemiology, University of Massachusetts, Amherst, MA, USA. shankinson@schoolph.umass.edu.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Hankinson
authors.affiliation: Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 181 Longwood Avenue, Boston, MA, 02115, USA. nhess@channing.harvard.edu.|Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA. nhess@channing.harvard.edu.|Applied Cancer Research - Institution for Translational Research Vienna (ACR-ITR VIEnna), Vienna, Austria. nhess@channing.harvard.edu.
authors.forename: Eva S
authors.initials: ES
authors.lastname: Schernhammer
mesh_terms: D000328:Adult; D015992:Body Mass Index; D049628:Body Size; D002940:Circadian Rhythm / Q000502:physiology*; D015331:Cohort Studies; D003404:Creatinine / Q000652:urine; D005260:Female; D006282:Health Personnel / Q000706:statistics & numerical data*; D006801:Humans; D008550:Melatonin / Q000031:analogs & derivatives* / Q000652:urine; D008875:Middle Aged; D049629:Waist-Hip Ratio; D014940:Work Schedule Tolerance / Q000502:physiology*; D016526:Workload; D055815:Young Adult
chemical_list: C054513:6-sulfatoxymelatonin; D003404:Creatinine; D008550:Melatonin