Blood pressure categories and mortality during a thirty-six-year follow-up

The aim of this study was to assess the mortality rate and risk of death in relation to the blood pressure (BP) categories during 36 years of follow-up period. 265 healthy middle-aged participants were included in the follow up for 36 years; 136 deaths occurred during this time. Causes of death (myocardial infarction (MI), stroke and other causes) were obtained from the death certificates. Participants were divided into four groups according to their blood pressure measurements (normal blood pressure, prehypertension, stage I and stage II hypertension). Hazard ratios (HR) for mortality from all investigated causes of death were calculated using measurements of normal BP as a reference. Kaplan-Meier method was used to calculate probability of survival for each BP category. Participants with prehypertension and stage I hypertension have shared similar all-cause mortality rates (15 deaths per 1000 person-years), and MI mortality rates (7 per 1000 person-years). Participants with stage II hypertension had the highest risk of all-cause mortality (HR 2.78, 95% confidence interval 1.16 to 6.66). Prehypertension and stage I hypertension induced similar rates of mortality due to myocardial infarction or all-causes. The survival probabilities were lower for participants with hypertension and prehypertension in comparison with those who had normal blood pressure. Participants with stage II hypertension had the highest mortality rates and the lowest probability of survival during a 36-year follow-up period.