The relationship between blood pressure and mortality in the oldest old

OBJECTIVES: To explore the relationship between systolic and diastolic blood pressure and risk of 6-year, all-cause mortality in men and women age 65 to 84 versus those 85 and older. DESIGN: A population-based longitudinal study. SETTING: This study was conducted at four different sites: East Boston, Massachusetts; New Haven, Connecticut; two rural counties in Iowa; and Piedmont, North Carolina. PARTICIPANTS: 12,802 community-dwelling persons age 65 and older. MEASUREMENTS: Baseline measurements collected include demographics, self-reported chronic medical conditions, blood pressure measurements, medications, health habits, and hospitalizations. RESULTS: Unadjusted actuarial survival analyses show that men age 65 to 84 years with systolic blood pressure <130 mmHg have significantly lower mortality compared with those with systolic blood pressure ≥180 mmHg (P < .0001). In contrast, men 85 and older with systolic blood pressure ≥180 mmHg have significantly lower mortality compared with those with systolic blood pressure <130 mmHg (P < .0001). In Cox proportional hazards analyses controlling for other predictors of survival, the hazard of death associated with each 10-mmHg increase in systolic blood pressure is positively associated among men age 65 to 84 years and negatively associated among men age 85 and older (Hazard ratio and 95% confidence interval (CI): 1.04 (1.01, 1.07) for younger men vs 0.92 (0.86, 0.99) for older men). Among women age 65 to 84, the hazard of death significantly increased with increase in systolic blood pressure (P < .0001), while there was no relationship between level of systolic blood pressure and survival in women 85 and older. Both men 65 to 84 years old and those 85 and older showed a negative relationship between diastolic blood pressure and all-cause mortality (Hazard ratio 0.93, 95% CI (0.88-0.97) for men age 65-84 years, and Hazard ratio 0.90, 95% CI 0.80-1.02 for men 85 and older). CONCLUSION: In men age 85 and older, higher systolic blood pressure is associated with better survival.