Routinely recorded blood pressures and prognosis in older adults

Problem

RCTs have provided evidence that aiming to lower Systolic Blood Pressure (SBP) to <120mmHg in selected older adults free from frailty is associated with improved cardiovascular and mortality outcomes. However, outcomes in routine care are less clear, especially on prognosis in older adults with frailty or with co-existing Chronic Kidney Disease (CKD). To work towards a more personalised approach to BP management in older adults, we must understand the implications of frailty status or co-existing conditions on prognosis.

We aimed to estimate the association of BP with cardiovascular and mortality outcomes in older adults with treated hypertension, those with CKD and by frailty status.

Approach

The 3 prospective observational studies presented used primary care clinical records from the Clinical Practice Research Datalink, linked to hospital and death certification data. Median SBP recorded in primary care during 3 years before study entry represented baseline SBP. The studies investigated: adults over 80 with diagnosed hypertension, adults over 60 with CKD 3 or 4 and adults over 75, stratified by baseline electronic frailty index (eFI) frailty status. Outcomes were incident cardiovascular events (myocardial infarction, heart failure, stroke) and all-cause mortality during follow-up. We used Cox proportional hazards models to estimate associations between baseline SBP and mortality and Fine and Gray competing risk models for cardiovascular outcomes, with all-cause mortality as the competing risk.

Findings

Results:

The studies included 79,376 with diagnosed hypertension, 158,713 with CKD and 415 980 for frailty stratification respectively. We showed increased incident cardiovascular outcomes with baseline hypertension in all studies as expected.

However, all-cause mortality did not follow the same pattern. Consistently across all 3 studies there was worse prognosis with lower baseline SBP: eg. all-cause mortality HR 1.25 SBP <135 mmHg, 95% confidence interval 1.19-1.31 for 80+ hypertension compared to 135 to 145mmHg reference, in CKD 3 and 4 higher HR mortality in 60+ years with SBP <120 compared to 130-140mmHg reference and across frailty groups higher HR mortality in 75+ with SBP <120 or 120 to 129mmHg compared to 130-140 mmHg reference.

In the frailty stratification study individuals with SBPs between 140 and 160mmHg had lower all-cause mortality during follow-up across baseline frailty status (eg. SBP 140 to 149 mmHg compared to 130 to 139 mmHg reference mild frailty Hazard Ratio (HR)=0.88, 0.86 to 0.91; severe frailty HR=0.77, 0.61 to 0.98). In those with moderate or severe frailty at baseline mortality remained lower even with SBP 160-169 mmHg at baseline.

Conclusions:

SBP >140 mmHg were associated with worse cardiovascular prognoses. However, this did not result in increased mortality during up to 10 years follow-up, including in severely frail groups and those with CKD.

Consequences

We must be cautious extrapolating results of studies in less representative participants to older adults.

Further work is required to explore optimum BP management in older adults, this may have important safety implications.