Abstract 049: The Effect Of Temperate Seasonality On Systolic Blood Pressure Is Amplified In Population Control Rates

Abstract

Background: Temperate seasonal effects have a significant influence on blood pressure (BP). Changes in average systolic (S)BP have an exaggerated effect on population BP control (BP <140/90) rates, in part due to patients bordering the control target. We assessed the influence of seasonal effects on average SBP, as well as the corresponding effect on control rates across a patient cohort. Methods: A prospective patient cohort was selected from six diverse healthcare organizations engaged in a quality improvement program. Patients with a diagnosis of hypertension (HTN), no medication changes, and at least one visit in each temperate season during the assessment period were included. The seasonal effect on average SBP and control was determined from multivariable mixed effects linear and logistic regression models, respectively. Results: A cohort of 60,676 patients, mean age 62.3±12.0 years, meeting all inclusion criteria was selected. The population had 453,787 qualifying visits, where SBP during winter months averaged 0.47 mmHg higher (95% CI [0.364-0.573]) than the yearly mean, with a significantly lower odds ratio for BP control (OR 0.92, 95% CI [0.91-0.94]). In contrast, average SBP was 0.92 mmHg lower during the summer - with a higher likelihood of BP control (OR 1.10, 95% CI [1.07-1.12]). Conclusion: The seasonal effect on SBP was confirmed in a diverse group of adults with hypertension. The novel observation is the nearly 5% variation in BP control related to seasonal SBP variation of 1.4 mmHg. From a practical perspective, BP control is typically defined by values at the last visit of the calendar year, which occur disproportionately in months with higher SBP and lower control.