Incidence of hypertension in a prospective cohort study of adults from Porto, Portugal

Background During the past 30 years, Portugal has been described as one of the countries with highest median blood pressure levels in Europe, but the incidence of hypertension is unknown. The aim of this study was to estimate the incidence of hypertension, according to socio-demographic characteristics and lifestyles. Methods A population-based cohort of randomly selected dwellers from Porto, Portugal, aged ≥18 years, was assembled in 1999–2003 (EPIPorto study) and 796 hypertension-free individuals (62.6% women) were reassessed after a median of 3.8 years. Hypertension was defined as blood pressure ≥140/90 mmHg and/or antihypertensive drug therapy. Incidence rate ratios (IRR) were estimated using Poisson regression. Results The overall incidence rate was 47.3 [95% confidence interval (95% CI): 40.5-55.5] per 1000 person-years. Among women, the incidence was 43.4 (35.6-53.1) and among men 52.7 (41.3-68.0) per 1000 person-years. The incidence was lower in women up to 60 years and much higher among women above 60 (110.0 vs. 64.4 per 1000 person-years among men, p for age-sex interaction=0.032). Participants with higher education had a lower risk of becoming hypertensive (≥13 years vs. ≤4 years: RR=0.70, 95% CI, 0.46-1.08, p for linear trend <0.001), independently of age and sex. Overweight and obesity were associated with a 1.67-fold and 2.44-fold increased risk of hypertension, respectively, independently of age, sex and education. Conclusions In this urban Portuguese population the incidence rate of hypertension was high, with new cases occurring predominantly among older subjects, the less educated and those with overweight-obesity. Despite recent progresses in blood pressure related outcomes, the risk of hypertension remains higher in Portugal than in other developed countries.