title: Migration and geographic variations in blood pressure in Britain.
abstract: OBJECTIVE
  To evaluate the relative contributions of factors acting at different stages in life to regional differences in adult blood pressure.
  
  
  METHODS
  Prospective cohort study (British regional heart study).
  
  
  METHODS
  One general practice in each of 24 towns in Britain.
  
  
  METHODS
  7735 Men aged 40-59 years when screened in 1978-80 whose geographic zone of birth and zone of examination were classified as south of England, midlands and Wales, north of England, and Scotland. Non-migrants (n = 3144) were born in the town where they were examined; internal migrants (n = 4147) were born in Great Britain but not in the town where they were examined; and international migrants (n = 422) were born outside Great Britain.
  
  
  METHODS
  Systolic and diastolic blood pressures and height.
  
  
  RESULTS
  Regardless of where they were born, men living in the south of England had lower mean blood pressures than men living in Scotland (142.5/80.1 v 148.1/85.2 mm Hg). The effects of the place of birth and place of examination on adult blood pressure were examined in a multiple regression model. For internal migrants the modelled increase in mean systolic blood pressure across adjacent zones of examination was 2.1 mm Hg (95% confidence interval 1.3 to 2.9); for adjacent zones of birth the corresponding increase was 0.1 mm Hg (-0.7 to 0.7). The place of examination seemed to be a far more important determinant of mean adult blood pressure than the place of birth. Height is an accepted marker of genetic and early life influences. Regional differences in height were therefore analysed to test whether the multiple regression model could correctly distinguish between the influence of place of birth and place of examination. As expected, men born in Scotland were shorter on average than men born in the south of England irrespective of where they lived in Britain (172.6 cm v 175.1 cm for internal migrants).
  
  
  CONCLUSIONS
  Regional variations in blood pressure were strongly influenced by where the men had lived for most of their adult lives rather than by where they were born and brought up. Among middle aged men, factors acting in adult life seemed to be more important determinants of regional differences in blood pressure than those acting early in life such as genetic inheritance, intrauterine environment, and childhood experience.
authors.affiliation: Department of Clinical Epidemiology and General Practice, Royal Free Hospital School of Medicine, London.
authors.forename: J
authors.initials: J
authors.lastname: Elford
authors.forename: A
authors.initials: A
authors.lastname: Phillips
authors.forename: A G
authors.initials: AG
authors.lastname: Thomson
authors.forename: A G
authors.initials: AG
authors.lastname: Shaper
mesh_terms: D000328:Adult; D001794:Blood Pressure; D001827:Body Height; D004739:England; D004777:Environment; D005843:Geography; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012111:Residence Characteristics; D012606:Scotland; D014171:Transients and Migrants; D014852:Wales