LOW BLOOD-PRESSURE AND MORTALITY IN THE ELDERLY - A 6-YEAR FOLLOW-UP OF 18,022 NORWEGIAN MEN AND WOMEN AGE 65 YEARS AND OLDER

Several studies have shown that low blood pressure in individuals age 65 years and older is related to increased overall mortality. We hypot hesize that this association is secondary to serious underlying illnes s, which has caused blood pressure reduction and, subsequently, has in creased the risk of dying. Our study population was comprised of indiv iduals age 20 years and older in the county of Nord Trondelag in Norwa y, who were studied in a general health survey between 1984 and 1986. We had measurements of blood pressure, blood glucose, weight, height, and other information for 9,732 women and 8,290 men age 65 years or ol der. During approximately 6 years of follow up, 2,122 women and 2,578 men died. For both genders, low systolic pressure was not associated w ith increased mortality, and the mortality curve did not display a J-s haped relation, after adjustment for age, marital status, body mass in dex, blood glucose, self-assessed health, use of antihypertensive medi cation, and history of diabetes and cardiovascular diseases. For diast olic pressure, however, women in the lowest category (<75 mmHg) had an adjusted mortality rate ratio of 1.21 (95% confidence limits 1.05, 1. 39), compared with reference women (80-87 mmHg). Among men, the analog ous mortality rate ratio was 1.16 (95% confidence limits = 1.02, 1.31) . To reduce further the potential confounding between diastolic pressu re and underlying illness, we excluded users of antihypertensive medic ation as well as the 2 first years of follow up. After these procedure s, the J-shaped mortality curve was not present among women, and it wa s substantially reduced among men. Thus, the results for both men and women indicated that the age-adjusted J-shaped relation between diasto lic blood pressure and mortality was confounded with indicators of ill health, and that the often found association between low diastolic bl ood pressure and increased mortality is indirect, possibly caused by s erious underlying disease.