title: Impact of urbanisation and altitude on the incidence of, and risk factors for, hypertension.
abstract: Most of the data regarding the burden of hypertension in low-income and middle-income countries comes from cross-sectional surveys instead of longitudinal studies. We estimated the incidence of, and risk factors for, hypertension in four study sites with different degree of urbanisation and altitude.
  
  
  
  Data from the CRONICAS Cohort Study, conducted in urban, semiurban and rural areas in Peru, was used. An age-stratified and sex-stratified random sample of participants was taken from the most updated census available in each site. Hypertension was defined as systolic blood pressure ≥140 mm Hg, or diastolic blood pressure ≥90 mm Hg, or self-report physician diagnosis and current treatment. The exposures were study site and altitude as well as modifiable risk factors. Incidence, incidence rate ratios (IRRs), 95% CIs and population-attributable fractions (PAFs) were estimated using generalised linear models.
  
  
  
  Information from 3237 participants, mean age 55.8 (SD±12.7) years, 48.4% males, was analysed. Overall baseline prevalence of hypertension was 19.7% (95% CI 18.4% to 21.1%). A total of 375 new cases of hypertension were recorded, including 5266 person-years of follow-up, with an incidence of 7.12 (95% CI 6.44 to 7.88) per 100 person-years. Individuals from semiurban site were at higher risk of hypertension compared with highly urbanised areas (IRR=1.76; 95% CI 1.39 to 2.23); however, those from high-altitude sites had a reduced risk (IRR=0.74; 95% CI 0.58 to 0.95). Obesity was the leading risk factor for hypertension with a great variation according to study site with PAF ranging from 12.5% to 42.4%.
  
  
  
  Our results suggest heterogeneity in the progression towards hypertension depending on urbanisation and site altitude.
authors.affiliation: CRONICAS Center of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Antonio
authors.initials: A
authors.lastname: Bernabé-Ortiz
authors.affiliation: CRONICAS Center of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: Rodrigo M
authors.initials: RM
authors.lastname: Carrillo-Larco
authors.affiliation: CRONICAS Center of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, USA.|Área de Investigación y Desarrollo, Asociación Benéfica PRISMA, Lima, Peru.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Gilman
authors.affiliation: CRONICAS Center of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|Division of Pulmonary and Critical Care, School of Medicine, Johns Hopkins University, Baltimore, USA.
authors.forename: William
authors.initials: W
authors.lastname: Checkley
authors.affiliation: Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Liam
authors.initials: L
authors.lastname: Smeeth
authors.affiliation: CRONICAS Center of Excellence in Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.|Department of Medicine, School of Medicine, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: J Jaime
authors.initials: JJ
authors.lastname: Miranda
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006973:Hypertension / Q000453:epidemiology*; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010568:Peru / Q000453:epidemiology; D015995:Prevalence; D011446:Prospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012424:Rural Population; D057566:Self Report; D014507:Urbanization / Q000639:trends