Incidence of hypertension and its risk factors in rural Kerala, India: a community-based cohort study

Objectives: To investigate the incidence of hypertension and its risk factors in Kerala, India where the epidemiological transition is more advanced than elsewhere in India.

Study design: Prospective cohort study.

Methods: A sample of 297 individuals (aged 15-64 years) in rural Kerala, India, who were free of hypertension at study enrolment, were followed-up from 2003 to 2010. At enrolment, demographic characteristics and behavioural risk factors were determined by interview, and the participants underwent physical (blood pressure, height, weight and waist circumference) and biochemical examinations (fasting plasma glucose and serum lipids). At follow-up, blood pressure readings were repeated using the original tool following the same protocol.

Results: Nearly one-quarter (23.6%) of the sample developed hypertension over a mean follow-up period of 7.1 (standard deviation 0.2) years. Age ≥35 years [relative risk (RR) 4.00, 95% confidence interval (CI) 2.37-6.03], current smoking [RR 1.99, 95% CI 1.14-2.97, population-attributable risk percent (PAR%) 13.3%], high-normal blood pressure (RR 3.53 vs optimal blood pressure, 95% CI 2.17-5.28, PAR% 44.0%) and central obesity (RR 2.45, 95% CI 1.45-3.70, PAR% 40.4%) were significantly associated with incident hypertension. Collectively, current smoking, high-normal blood pressure and central obesity accounted for 70.1% of all new cases of hypertension. Awareness, treatment and control rates of incident hypertension were 42.9%, 22.9% and 11.4%, respectively.

Conclusions: This rural sample showed a high incidence of hypertension. This underscores the need for primary prevention of hypertension through lifestyle modification strategies targeting individuals with high-normal blood pressure, central obesity and current smoking. The healthcare system needs to improve the level of awareness, treatment and control of hypertension in this population.