Which BP measurements best predict mortality? – New Data
The authors at CRL have published and blogged on the association of BP measured for an insurance exam and long-term mortality. Results showed the importance of systolic BP even as low as 120 mm Hg on mortality and the lack of association with diastolic BP, finding at odds with clinical practice at the time and most underwriting guides but confirmed by more recent non-insurance studies.
However, we lacked information on other sources of BP measurements and a recent study in Lancet has helped remedy this. It utilized the Spanish Ambulatory Blood Pressure Registry including information on age, sex, BMI, multiple BP measurements in clinic and 24-hour BP monitoring and was linked to the very complete Spanish death registry.
After adjustment for confounders, there was a high association with night-time and slightly lower association with 24 hr systolic BP measurements and mortality, but far less association for clinic BP measurements which on average ran 10 to 20 mm Hg higher. Mortality hazard ratio per each SD increase in BP was highest for night-time (1.46), then 24 hour (1.41), followed by daytime (1.35) and trailed badly by clinic BP (1.11). The poor showing of clinic measurements is likely related to both white coat hypertension and sometimes missing hypertension picked up on 24-hour monitoring. The data also confirmed that increasing diastolic BP did not predict risk. In fact, risk increased as diastolic BP fell (or maybe a “u” shaped curve) which resulted in higher pulse pressure (see CRL paper linked above for further information on pulse pressure and mortality).
Accurate assessment of BP risk is dependent on the averaged BP over time and use of measurements outside those done in the clinic (is the insurance exam BP better?) is most helpful. Given the time and cost of lifetime BP Rx and the health cost associated with missing even modest but sustained elevations of BP, getting it right may require BP measurements at different times and places.
About the Author
Michael Fulks, MD, Consulting Medical Director, is board-certified in internal and insurance medicine. After leaving practice, he served as a medical director, creating or editing several underwriting manuals and preferred programs. More recently, Mike has consulted for CRL participating in its mortality research on laboratory test results, BP and build, and in the development of risk-scoring tools for laboratory and non-laboratory data.