Rethinking the association of high blood pressure with mortality in elderly adults: the impact of frailty

Abstract

Background: The association of hypertension and mortality is attenuated in elderly adults. Walking speed, as a measure of frailty, may identify which elderly adults are most at risk for the adverse effects of hypertension. We hypothesized that elevated blood pressure (BP) would be associated with a greater risk of mortality in faster-, but not slower-, walking older adults.

Methods: Participants included 2340 persons 65 years and older in the National Health and Nutrition Examination Survey, 1999-2000 and 2001-2002. Mortality data were linked to death certificates in the National Death Index. Walking speed was measured over a 20-ft (6 m) walk and classified as faster (≥ 0.8 m/s [n = 1307]), slower (n = 790), or incomplete (n = 243). Potential confounders included age, sex, race, survey year, lifestyle and physiologic variables, health conditions, and antihypertensive medication use.

Results: Among the participants, there were 589 deaths through December 31, 2006. The association between BP and mortality varied by walking speed. Among faster walkers, those with elevated systolic BP (≥ 140 mm Hg) had a greater adjusted risk of mortality compared with those without (hazard ratio [HR], 1.35; 95% CI, 1.03-1.77). Among slower walkers, neither elevated systolic nor diastolic BP (≥ 90 mm Hg) was associated with mortality. In participants who did not complete the walk test, elevated BP was strongly and independently associated with a lower risk of death: HR, 0.38; 95% CI, 0.23-0.62 (systolic); and HR, 0.10; 95% CI, 0.01-0.81 (diastolic).

Conclusions: Walking speed could be a simple measure to identify elderly adults who are most at risk for adverse outcomes related to high BP.

Figure 1

Kaplan-Meier survival plots of persons with elevated 1) systolic > 140 mmHg (top) and b) diastolic >90 mmHg (bottom) blood pressure, stratified by walking speed, in NHANES participants aged 65 and older (1999–2002) followed until December 31^st, 2006

Figure 2

Sensitivity analyses of the association of elevated systolic BP (>140 mmHg) and mortality, stratified by walking speed, in NHANES participants aged 65 and older (1999–2002) followed until December 31^st, 2006.