Functional Status Modifies the Association of Blood Pressure with Death in Elders: Health and Retirement Study

Abstract

Objective: To examine whether grip strength, gait speed, and the combination of the two physical functioning measures modified the association of systolic BP (SBP) and diastolic BP (DBP) with mortality.

Design: Nationally representative cohort study.

Setting: Health and Retirement Study.

Participants: 7,492 U.S. adults aged ≥65 years.

Measurements: Grip strength was measured by a hand dynamometer and classified as normal (≥16 kg for female; ≥26 kg for male) and weak. Gait speed was assessed over a 98.5-inch walk and classified as non-slow (≥0.60 m/s for female; ≥0.52 m/s for male) and slow.

Results: Over an average follow-up time of 6.0 years, 1,870 (25.0%) participants died. After adjustment for socio-demographic, behavioral, and clinical measures, elevated SBP (≥150 mmHg) and DBP (≥90 mmHg) was associated with a 24% (95% CI, 7-43%) and 25% (95% CI, 5-49%) higher mortality among participants with normal grip strength. In contrast, elevated SBP and DBP was associated with a 6% (95% CI, 31 to -27%) and a 16% (95% CI, 46 to -26%) lower mortality among those with weak grip strength (P-values of interactions: both=.07). The inverse relations between BP with death were most pronounced among slow walkers with weak grip strength. The HRs of elevated SBP and DBP for death was 0.85 (95% CI, 0.56-1.29) and 0.53 (95% CI, 0.30-0.96), respectively, and was substantially different from non-slow walkers with normal grip strength (HR = 1.24 and 1.15, respectively; P-values of interactions: both <.001). Therefore, associations of BP with death varied modestly by gait speed.

Conclusion: Grip strength modified the association of BP with death. Combination of grip strength and gait speed has incremental value for modifying the association of BP with death.

Keywords: blood pressure; gait speed; grip strength; mortality.