Effects of Age and Functional Status on the Relationship of Systolic Blood Pressure With Mortality in Mid and Late Life: The ARIC Study.

Background: Impaired functional status attenuates the relationship of systolic blood pressure (SBP) with mortality in older adults but has not been studied in middle-aged populations.
Method: Among 10,264 stroke-free Atherosclerosis Risk in Communities participants (mean age 62.8 [5.7] years; 6,349 [62%] younger [<65 years]; 5,148 [50%] men; 2,664 [26%] Black), function was defined as good function (GF) for those self-reporting no difficulty performing functional tasks and basic or instrumental tasks of daily living; all others were defined as impaired function (IF). SBP categories were normal (<120 mmHg), prehypertension (120-139 mmHg), and hypertension (≥140 mmHg). Mortality risk associated with SBP was estimated using adjusted Cox proportional hazard models with a triple interaction between age, functional status, and SBP.
Results: Mean follow-up was 12.9 years with 2,863 (28%) deaths. Among younger participants, 3,017 (48%) had IF; 2,279 of 3,915 (58%) older participants had IF. Prehypertension (hazard ratio [HR] = 1.48 [1.03, 2.15] p = .04) and hypertension (HR = 1.97 [1.29, 3.03] p = .002) were associated with mortality in younger GF and older (≥65 years) GF participants (prehypertension HR = 1.21 [1.06, 1.37] p = .005; hypertension HR = 1.47 [1.36, 1.59] p < .001). Among IF participants, prehypertension was not associated with mortality in younger participants (HR = 0.99 [0.85, 1.15] p = .93) and was protective in older participants (HR = 0.87 [0.85, 0.90] p < .001). Hypertension was associated with mortality in younger IF participants (HR = 1.54 [1.30, 1.82] p < .001) but not in older IF participants (HR = 0.99 [0.87, 1.14] p = .93).
Conclusions: Compared with younger and well-functioning persons, the additional contribution of blood pressure to mortality is much lower with older age and impaired function, particularly if both are present. Functional status and age could potentially inform optimal blood pressure targets.
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