Incidence and risk factors of isolated systolic and diastolic hypertension: a 10 year follow-up of the Tehran Lipids and Glucose Study.

The objective of this study is to examine the incidence and risk factors of isolated systolic hypertension (ISH) and isolated diastolic hypertension (IDH) in a Middle Eastern population, during a median follow-up of 9.6 years. In total, 8573 subjects without hypertension, cardiovascular disease and known diabetes were recruited into the study. To calculate the incidence of ISH, those with diastolic blood pressure (DBP) ≥ 90 mmHg during follow-up, and for calculating IDH those with systolic blood pressure (SBP) ≥ 140 mmHg during follow-up, were excluded. During follow-up, 235 new cases of ISH were identified, with a crude incidence rate of 5.7/1000 person-years; the corresponding values for IDH were 470 and 10.9/1000 person-years. Using backward stepwise Cox regression analysis, older age, baseline SBP and body mass index were related to incident ISH. Regarding IDH, younger age, baseline DBP and waist circumference were associated with higher risk, whereas female gender and being married were associated with lower risk (all p < 0.05). The C-statistics for the prediction model were 0.91 for ISH and 0.76 for IDH. In conclusion, after a decade of follow-up of this Iranian population, we found an incidence of about 0.5% and 1% per year for ISH and IDH, respectively.