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

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.