Low blood pressure is not an independent determinant of survival in an elderly population

The object of the study was to determine whether the increased mortality associated with low blood pressure in elderly people arises because of the adverse effects of hypotension or because of confounding variables. A community sample of 782 people aged 70 years and older was followed for 3 years. Blood pressure measurements were taken on initial assessment and hypotension was defined separately for systolic and diastolic pressures as a pressure less than the tenth percentile for the sample (systolic less than or equal to 122 mmHg, diastolic less than or equal to 68 mmHg). After 3 years 135 participants had died and of these 31 had low systolic or diastolic blood pressure at baseline. Low diastolic pressure was associated with an increased mortality over the 3 years (hazard ratio 1.85, 95% Confidence Interval 1.18-2.91). This increase in risk was explained by confounding variables. Low systolic pressure was not associated with increased mortality. The increased mortality of those with low blood pressure is explained by concurrent illness.