Health risk factors and the incidence of hypertension: 4-year prospective findings from a national cohort of 60 569 Thai Open University students

OBJECTIVE This study evaluates the impact of a number of demographic, biological, behavioural and lifestyle health risk factors on the incidence of hypertension in Thailand over a 4-year period. DESIGN A 4-year prospective study of health risk factors and their effects on the incidence of hypertension in a national Thai Cohort Study from 2005 to 2009. SETTING As Thailand is transitioning from a developing to a middle-income developed country, chronic diseases (particularly cardiovascular disease) have emerged as major health issues. Hypertension is a major risk factor for heart attack and stroke and cross-sectional studies have indicated that the prevalence is increasing. STUDY PARTICIPANTS A total of 57 558 Sukhothai Thammathirat Open University students who participated in both the 2005 and 2009 questionnaire surveys and who were normotensive in 2005 were included in the analysis. MEASURES Adjusted relative risks associating each risk factor and incidence of hypertension by sex, after controlling for confounders such as age, socioeconomic status, body mass index (BMI) and underlying diseases. RESULTS The overall 4-year incidence of hypertension was 3.5%, with the rate in men being remarkably higher than that in women (5.2% vs 2.1%). In both sexes, hypertension was associated with age, higher BMI and comorbidities but not with income and education. In men, hypertension was associated with physical inactivity, smoking, alcohol and fast food intake. In women, hypertension was related to having a partner. CONCLUSIONS In both men and women, hypertension was strongly associated with age, obesity and comorbidities while it had no association with socioeconomic factors. The cohort patterns of socioeconomy and hypertension reflect that the health risk transition in Thais is likely to be at the middle stage. Diet and lifestyle factors associate with incidence of hypertension in Thais and may be amenable targets for hypertension control programmes.