Systolic Blood Pressure Trajectory, Frailty and All-Cause Mortality Over 80 Years of Age. Cohort Study Using Electronic Health Records
Background—Clinical trials show benefit from lowering systolic blood pressure in people aged ≥80 years but non-randomised epidemiological studies suggest lower systolic blood pressure may be associated with higher mortality. This study aimed to evaluate associations of SBP with all-cause mortality by frailty category over 80 years of age and to evaluate SBP trajectories before death.
Methods—A population-based cohort study was conducted using electronic health records of 144,403 participants aged 80 and older registered with family practices in the United Kingdom from 2001 to 2014. Participants were followed for up to five years. Clinical records of systolic blood pressure (SBP) were analysed. Frailty status was classified, using the e-Frailty Index, into the categories of 'fit', 'mild', 'moderate' and 'severe' frailty. All-cause mortality was evaluated by frailty status and mean SBP in Cox proportional hazards models. SBP trajectories were evaluated using person months as observations, with mean SBP and antihypertensive treatment status estimated for each person month. Fractional polynomial models were used to estimate SBP trajectories over five years before death.
Results—There were 51,808 deaths during follow-up. Mortality rates increased with frailty level and were greatest at SBP <110 mm Hg. In 'fit' women, mortality was 7.7 per 100 person years at SBP 120-139 mm Hg, 15.2 at SBP 110-119 mm Hg and 22.7 at SBP <110 mm Hg; for women with 'severe' frailty, rates were 16.8, 25.2 and 39.6 respectively. SBP trajectories showed an accelerated decline in the last two years of life. The relative odds of SBP<120 mm Hg were higher in the last three months of life than five years previously both in treated (odds ratio 6.06, 95% confidence interval 5.40 to 6.81) and untreated patients (6.31, 5.30 to 7.52). There was no evidence of intensification of antihypertensive therapy in the final two years of life.
Conclusions—A terminal decline of SBP in the final two years of life suggests that non-randomized epidemiological associations of low SBP with higher mortality may be accounted for by reverse causation, if participants with lower blood pressure values are closer, on average, to the end of life.
- Received December 1, 2016.
- Revision received March 13, 2017.
- Accepted March 29, 2017.
Circulation is published on behalf of the American Heart Association, Inc., by Wolters Kluwer. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/), which permits use, distribution, and reproduction in any medium, provided that the original work is properly cited.