Twenty-year dynamics of hypertension in Iranian adults: age, period, and cohort analysis.

Hypertension is a well-known health problem all over the world. Many studies have assessed its prevalence and associated risk factors, but all were cross-sectional and did not evaluate the trend of hypertension through all three different temporal dimensions including age, period, and cohort. So, we aimed to assess the 20-year dynamics of hypertension via the age-period-cohort model. Data from 74,155 subjects aged 25-60 years gathered through five national health surveys (1990-91, 1999, 2003, 2007, and 2011) were used in this study. The age-period-cohort effect on hypertension was analyzed using the intrinsic estimator model. The prevalence of hypertension increased with age for both genders except for males in 2003 and 2011 periods with drops of 3.5% for ages 55-60 and 8.1% for ages 50-60, respectively. As for the period effect, the prevalence of hypertension was almost constant in all age groups for both genders from 1990-1999. The cohort-based prevalence of hypertension showed a declining trend in all cohorts for females except for 2011 in birth cohort of 1950-1955 which remains stationary. The trend of prevalence for males also follows a decreasing trend except for periods of 2003, 2007, and 2011; birth cohorts of 1945-1949, 1975-1980, and 1950-1960 increase by 3.5%, 1.9%, and 8.1%, respectively. The age effect on the prevalence of hypertension showed an almost monotonic increasing trend. The period effect increased the total prevalence of hypertension from 1992 to 1997. The cohort effect also showed a monotonic decrease in hypertension prevalence except for a few discrepancies.