Blood pressure and mortality in an older population. A 5-year follow-up of the Helsinki Ageing Study.

Abstract

Hypertension is an established risk factor of cardiovascular diseases, and in clinical studies its treatment has reduced cardiovascular complications in subjects up to 80 years of age. In the older age groups, prognostic data on blood pressure is sparse. We evaluated the prognostic significance of different blood pressure levels and the history of elevated blood pressure in an older population. In the Helsinki Ageing Study random individuals 75, 80, and 85 years of age (n = 521) were evaluated at baseline using postal questionnaires, structured interviews, clinical examinations, laboratory investigations, and blood pressure measurements (supine, seated, standing). Date of death during a 5-year follow-up was verified using computerized registers, and thus the follow-up was 100% complete. The data were analysed using life-table analyses and Cox proportional hazards models. At 5 years, 240 subjects (40%) had died, 50% of them of cardiovascular disease. In crude analyses, an inverse relationship between both systolic and diastolic blood pressure and mortality was observed in all groups combined (P < 0.01), and separately in the 80 and 85-year-old groups. However, a J-shaped link between diastolic blood pressure and mortality was found in the 75-year-old group. After controlling for age, gender and the presence of clinically significant diseases (in 72% of subjects) baseline blood pressure was associated with favourable 5-year survival. The risk ratios of systolic (per 10 mmHg) and diastolic blood pressure (per 5 mmHg) were 0.90 (95% CI 0.85-0.96) and 0.92 (95% CI 0.86-0.99), respectively. Neither isolated systolic hypertension nor a history of hypertension treatment were associated with 5-year survival. At the population level, among subjects aged 75 years and over, favourable 5-year survival is indicated by a high, but not a low, blood pressure.