title: Change in body mass index and its impact on blood pressure: a prospective population study.
abstract: BACKGROUND
  Overweight and obesity increase the risk of elevated blood pressure, but the knowledge of the effect of weight change on blood pressure is sparse.
  
  
  OBJECTIVE
  To investigate the association between change in body mass index (BMI) and change in diastolic blood pressure (DBP), systolic blood pressure (SBP), and hypertension status.
  
  
  METHODS
  Two population-based cross-sectional studies, one in 1984-86 and the other in 1995-97.
  
  
  METHODS
  The Nord-Trondelag Health Study (HUNT).
  
  
  METHODS
  We included 15,971 women and 13,846 men who were 20 y or older at the first survey, without blood pressure medication at both surveys and without diabetes, cardiovascular disease or dysfunction in daily life at baseline.
  
  
  METHODS
  Weight, height and blood pressure were measured standardised. Change in BMI was categorised as stable (initial BMI+/-0.1 kg/m2 each follow-up year), increased or decreased, and BMI was categorised by using World Health Organisation's categorisation (underweight BMI: <18.5 kg/m2, normal weight BMI: 18.5-24.9 kg/m2, overweight BMI: 25.0-29.9 kg/m2, obesity BMI> or =30 kg/m2).
  
  
  RESULTS
  An increase in BMI and a decrease in BMI were significantly associated with increased and decreased SBP and DBP, respectively, compared to a stable BMI in both genders and all age groups, although the strongest effect was found among those who were 50 y and older. The adjusted odds ratio for having hypertension at HUNT 2 was 1.8 (95% confidence interval (CI): 1.5, 2.2) among women and 1.6 (95% CI: 1.4,1.8) among men aged 20-49 y who increased their BMI compared to those who had stable BMI. A similar, but weaker association was found among women and men aged 50 y or more. The mean change in both SBP and DBP was higher for those who changed BMI category from first to the second survey than for those who were in the same BMI class at both surveys.
  
  
  CONCLUSIONS
  Our result supports an independent effect of change in BMI on change in SBP and DBP in both women and men, and that people who increase their BMI are at increased risk for hypertension.
authors.affiliation: Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway. b.drovyvold@medisin.ntnu.no
authors.forename: W B
authors.initials: WB
authors.lastname: Drøyvold
authors.forename: K
authors.initials: K
authors.lastname: Midthjell
authors.forename: T I L
authors.initials: TI
authors.lastname: Nilsen
authors.forename: J
authors.initials: J
authors.lastname: Holmen
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D003971:Diastole; D005260:Female; D006306:Health Surveys; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011446:Prospective Studies; D013599:Systole; D015431:Weight Loss / Q000502:physiology*