Evidence for a positive linear relation between blood pressure and mortality in elderly people.

Many studies of blood pressure in the elderly have found higher death rates in groups with the lowest blood pressure than in those with intermediate values. In a large community study, we examined whether these findings are real or artifacts of short follow-up, co-morbidity, or low blood pressure in people near death. In 1982-83, we assessed drug use, medical history, disability, physical function, and blood pressure in 3657 residents of East Boston, Massachusetts, aged 65 and older. We identified all deaths (1709) up to 1992 and followed up survivors for an average of 10.5 (range 9.5-11.0) years. After adjustment for confounding variables (including frailty and disorders such as congestive heart failure and myocardial infarction) and exclusion of deaths within the first 3 years of follow-up, higher systolic pressure predicted linear increases in cardiovascular (p < 0.0001) and total (p < 0.0007) mortality. Higher diastolic pressure predicted increases in cardiovascular (p = 0.006) but not total (p = 0.48) mortality. These results differed from those for the first 3 years, during which groups with the lowest systolic and diastolic pressures had the highest death rates. In the long term, lower blood pressure in old age, as in middle age, is associated with better survival. Short-term findings may differ because of associations of co-morbidity and frailty with blood pressure near death. Overall, the findings support recommendations to treat high blood pressure in elderly people.