Encounter frequency and blood pressure in hypertensive patients with diabetes mellitus

Abstract

The relationship between encounter frequency (average number of provider-patient encounters over a period of time) and blood pressure for hypertensive patients is unknown. We tested the hypothesis that shorter encounter intervals are associated with faster blood pressure normalization. We performed a retrospective cohort study of 5042 hypertensive patients with diabetes mellitus treated at primary care practices affiliated with 2 academic hospitals between 2000 and 2005. Distinct periods of continuously elevated blood pressure (>or=130/85 mm Hg) were studied. We evaluated the association of the average encounter interval with time to blood pressure normalization and rate of blood pressure decrease. Blood pressure of the patients with the average interval between encounters <or=1 month normalized after a median of 1.5 months at the rate of 28.7 mm Hg/month compared with 12.2 months at 2.6 mm Hg/month for the encounter interval >1 month (P<0.0001 for all). Median time to blood pressure normalization was 0.7 versus 1.9 months for the average encounter interval <or=2 weeks versus between 2 weeks and 1 month, respectively (P<0.0001). In proportional hazards analysis adjusted for patient demographics, initial blood pressure, and treatment intensification rate, a 1 month increase in the average encounter interval was associated with a hazard ratio of 0.764 for blood pressure normalization (P<0.0001). Shorter encounter intervals are associated with faster decrease in blood pressure and earlier blood pressure normalization. Greatest benefits were observed at encounter intervals (<or=2 weeks) shorter than what is currently recommended.

Figure 1. Encounter Interval and Time to Blood Pressure Normalization

Kaplan-Meier curves for time to normalization of blood pressure during a period of continuously elevated blood pressure were plotted for different average encounter intervals. Distinct periods of elevated blood pressure (from the first elevated to the first normal blood pressure) for the same patient were analyzed separately.

Figure 2

Figure 2A. Encounter Interval and Rate of Change of Systolic Blood Pressure The average monthly change in systolic (A) and diastolic (B) blood pressure, respectively, was plotted against the average encounter interval. Distinct periods of elevated blood pressure (from the first elevated to the first normal blood pressure) for the same patient were analyzed separately. Dotted lines indicate 95% confidence interval. Figure 2B. Encounter Interval and Rate of Change of Diastolic Blood Pressure

Figure 2

Figure 2A. Encounter Interval and Rate of Change of Systolic Blood Pressure The average monthly change in systolic (A) and diastolic (B) blood pressure, respectively, was plotted against the average encounter interval. Distinct periods of elevated blood pressure (from the first elevated to the first normal blood pressure) for the same patient were analyzed separately. Dotted lines indicate 95% confidence interval. Figure 2B. Encounter Interval and Rate of Change of Diastolic Blood Pressure

Figure 3. Effect of Patient and Encounter Characteristics on Encounter Interval

Circles indicate effect estimates from a multivariable model that included all variables displayed in the figure. Whiskers indicate 95% confidence intervals. “PCP” variable indicates that the encounter was with the patient’s primary care provider (as opposed to a covering physician). “Acute conditions” variable indicates the number of billing codes linked to the encounter that represented an acute complaint (most commonly acute pain or infection). “Commercial insurance” variable indicates that the patient’s health insurance was provided by a private company, as opposed to Medicare and/or Medicaid. “Rx Intensification” indicates whether anti-hypertensive treatment was intensified (a new medication started or the dose of an existing medication increased) during the encounter. *For every 10 mm Hg **for every 10 years