Impact of Therapeutic Inertia on Long-Term Blood Pressure Control

Antihypertensive drug treatment is based on stepped titration in response to elevated blood pressure (BP) measurements. However, measurements do not necessarily represent an individual’s true BP (due to random error and biological variability), and medications are not always increased when measurements are above target (therapeutic inertia). We developed a Monte Carlo model with a 10-year horizon to investigate how measurement error impacted systolic BP (SBP) control in the presence of therapeutic inertia. When SBP measurements were in the range 140 to 159 mm Hg, the probability of escalating treatment was determined by a Bernoulli probability mass function parameterized by weighting functions exploring distinct inertia profiles. Simulating inertia with the weighting function that approximated to clinical practice resulted in ≈50% of individuals failing to achieve their SBP target within the 10-year time horizon. An inverse relationship was observed between measurement error and SBP control. This suggests that the value of accurate SBP measurement is only realized if it changes the underlying probability of inertia—that is, patients/clinicians believe a measurement to be accurate and so are more likely to act upon it. Removal of inertia during treatment initiation (ie, stepped titration until SBP measurement was below target) improved true SBP control for all simulations. Our simulations show that the impact of therapeutic inertia during treatment initiation persists during long-term follow-up. Strategies to remove therapeutic inertia during treatment initiation (ie, dual antihypertensive therapy) are likely to improve long-term BP control irrespective of BP measurement technique.