Effect of blood pressure on the mortality of the elderly population with (pre)frailty: Results from NHANES 1999-2004

BackgroundsThe optimal blood pressure of elderly people with frailty or prefrailty is still unclear. We aimed to explore the relationship between blood pressure and mortality in the elderly with (pre)frailty. MethodsA total of 528 participants aged 60 years and older were exacted for analyses of the association between blood pressure and mortality from the database of the National Health and Nutrition Examination Survey (NHANES) (1999-2004). Kaplan-Meier curves and log-rank tests were used to investigate the differences in survival between groups. Multivariable Cox regression and restricted cubic spline (RCS) analyses were applied to explore the relationship between blood pressure and mortality. ResultsDuring the median follow-up time of 116.5 [interquartile range (IQR) of 60-186] months, 363 all-cause deaths and 122 cardiac deaths were documented. For all-cause mortality, more participants died with systolic blood pressure (SBP) < 110 mmHg and SBP >= 170 mmHg (log-rank p = 0.004). After adjusting for confounders, SBP < 110 mmHg [hazard ratio (HR) 1.52, 95% CI: 0.96-2.41] and SBP >= 170 mmHg (HR 1.53, 95% CI: 1.09-2.15) had higher risks of all-cause mortality compared with SBP within 130-150 mmHg. There were no significant differences in all-cause mortality among DBP categories. A J-curve association was identified between the SBP and hazard ratio for all-cause mortality (p for non-linear = 0.028), with 138.6 mmHg as the lowest hazard ratio of all-cause mortality; each 10 mmHg of SBP rise was associated with a 9% increased risk in all-cause mortality (HR 1.09, 95% CI 1.00-1.18). Additionally, a non-linear relationship was determined between SBP and the hazard ratio for cardiac deaths (p for non-linear = 0.030), with 140.1 mmHg as the lowest hazard ratio of cardiac deaths. When SBP was higher than 140.1 mmHg, each 10 mmHg rise in SBP was associated with a 17% increased risk of cardiac deaths (HR 1.17, 95% CI: 1.02-1.34). ConclusionBoth lower and higher SBP levels are associated with higher risks of all-cause mortality in older individuals with (pre)frailty. There are J-shaped associations between SBP and mortality, with the optimal SBP being approximately 140 mmHg for this population specifically.