title: Work schedule and physically demanding work in relation to menstrual function: the Nurses' Health Study 3.
abstract: OBJECTIVE
  This study aimed to evaluate occupational exposures and menstrual cycle characteristics among nurses.
  
  
  METHODS
  Using cross-sectional data collected in 2010-2012 from 6309 nurses aged 21-45 years, we investigated nurses' menstrual function in the Nurses' Health Study 3. We used multivariable regression modeling to analyze the associations between occupational exposures and prevalence of irregular cycles and long and short cycle lengths.
  
  
  RESULTS
  The cohort reported cycle length as <21 (1.5%), 21-25 (15.6%), 26-31 (69.7%), and 32-50 (13.2%) days. In addition, 19% of participants reported irregular cycles. Working ≥41 hours/week was associated with a 16% [95% confidence interval (95% CI): 4-29%] higher prevalence of irregular cycles and a higher prevalence of very short (<21-day) cycles [prevalence odds ratio (OR) 1.93, 95% CI 1.24-3.01] in adjusted models. Irregular menstrual cycles were more prevalent among women working nights only (32% higher; 95% CI 15-51%) or rotating nights (27% higher, 95% CI 10-47%), and was associated with the number of night shifts per month (P for trend <0.0001). Rotating night schedule was associated with long (32-50 day) cycles (OR 1.28, 95% CI 1.03-1.61). Heavy lifting was associated with a higher prevalence of irregular cycles (34% higher), and the prevalence of cycles <21 days and 21-25 day cycles increased with increasing heavy lifting at work (P for trend <0.02 for each endpoint).
  
  
  CONCLUSIONS
  Night work, long hours, and physically demanding work might relate to menstrual disturbances.
authors: National Institute for Occupational Safety and Health 1090 Tusculum Ave, MS R-15, Cincinnati, OH 45226, USA. clawson@cdc.gov.
authors: Christina C
authors: CC
authors: Lawson
authors: Candice Y
authors: CY
authors: Johnson
authors: Jorge E
authors: JE
authors: Chavarro
authors: Eileen N
authors: EN
authors: Lividoti Hibert
authors: Elizabeth A
authors: EA
authors: Whelan
authors: Carissa M
authors: CM
authors: Rocheleau
authors: Barbara
authors: B
authors: Grajewski
authors: Eva S
authors: ES
authors: Schernhammer
authors: Janet W
authors: JW
authors: Rich-Edwards
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D005298:Fertility / Q000502:physiology; D006801:Humans; D008597:Menstrual Cycle / Q000502:physiology*; D008599:Menstruation Disturbances / Q000209:etiology* / Q000503:physiopathology; D008875:Middle Aged; D009741:Nursing Staff, Hospital / Q000706:statistics & numerical data; D016273:Occupational Exposure; D016272:Occupational Health; D013315:Stress, Psychological / Q000150:complications*; D014940:Work Schedule Tolerance; D055815:Young Adult