title: Shift work is not associated with high blood pressure or prevalence of hypertension.
abstract: BACKGROUND
  Working mostly at night has been suggested to be associated with upset of chronobiological rhythms and high blood pressure, but the evidence from epidemiological studies is weak.
  
  
  METHODS
  In a cross-sectional survey, we evaluated the association between shift work and blood pressure, pre-hypertension and hypertension. In total, 493 nurses, nurse technicians and assistants, were selected at random in a large general hospital setting. Hypertension was diagnosed by the mean of four automatic blood pressure readings≥140/90 mmHg or use of blood pressure lowering agents, and pre-hypertension by systolic blood pressure≥120-139 or diastolic blood pressure≥80-89 mmHg. Risk factors for hypertension were evaluated by a standardized questionnaire and anthropometric measurements. The association between the shift of work and blood pressure, pre-hypertension and hypertension was explored using univariate and multivariate analyses that controlled for risk factors for hypertension by covariance analysis and modified Poisson regression.
  
  
  RESULTS
  The mean age of the participants was 34.3±9.4 years and 88.2% were women. Night shift workers were older, more frequently married or divorced, and less educated. The prevalence of hypertension in the whole sample was 16%, and 28% had pre-hypertension. Blood pressure (after adjustment for confounding) was not different in day and night shift workers. The prevalence of hypertension and pre-hypertension by shift work was not different in the univariate analysis and after adjustment for confounding (all risk ratios=1.0).
  
  
  CONCLUSIONS
  Night shift work did not increase blood pressure and was not associated with hypertension or pre-hypertension in nursing personnel working in a large general hospital.
authors.affiliation: Postgraduate Program in Medical Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Carla
authors.initials: C
authors.lastname: Sfreddo
authors.forename: Sandra Costa
authors.initials: SC
authors.lastname: Fuchs
authors.forename: Alvaro Roberto
authors.initials: AR
authors.lastname: Merlo
authors.forename: Flávio Danni
authors.initials: FD
authors.lastname: Fuchs
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009726:Nurses; D015995:Prevalence; D012307:Risk Factors; D014937:Work; D014940:Work Schedule Tolerance / Q000502:physiology*