Recommended BP Thresholds to Prevent Coronary Artery Disease in Patients With T1D

Normal blood pressure 120/80 on an LCD screen
Researchers aimed to determine the optimal BP threshold to minimize the risk for coronary artery disease events in young patients with childhood-onset T1D.

Having blood pressure (BP) ≥120/80 mm Hg was associated with a two-fold increase in risk for long-term coronary artery disease (CAD) events in patients with type 1 diabetes (T1D), according to study results published in Diabetes Care.

As patients with T1D are at increased risk for CAD compared with the general population, elevated BP may have an impact on cardiovascular outcomes. Current guidelines from the American Diabetes Association recommend BP targets of 130/80 mm Hg in patients with diabetes at high risk for cardiovascular disease and 140/90 mm Hg in patients at low cardiovascular risk.

However, there are limited data regarding the impact of chronically elevated BP on CAD events in patients with T1D. The goal of this study was to determine the optimal BP threshold to minimize risk for CAD events in young patients with childhood-onset T1D.

Of 658 eligible participants from the Pittsburgh Epidemiology of Diabetes Complications Study — a prospective cohort of patients with childhood-onset T1D — 605 participants (mean age, 27 years; 49.8% women) had no history of CAD at study entry and were enrolled in the study. Follow-up continued to first CAD event, death, or the 25th year of the cohort study (2011-2014).

Status of CAD was evaluated biennially during the study period and BP was measured by sphygmomanometer for the first 10 years of the study, after which an aneroid device was used. The cumulative BP (mm Hg-years) was the sum of mean BP from two consecutive follow-up visits multiplied by the time interval (years) between the visits. Time-weighted BP was calculated by dividing cumulative BP by the total follow-up time. Risk stratification analyses were performed on the basis of time-weighted BP (<120/80 mm Hg vs ≥120/80 mm Hg) and glycated hemoglobin (<8% vs ≥8%).

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The results indicated a dose-gradient association between time-weighted BP and incident CAD. Time-weighted systolic and diastolic BP, starting from approximately 120 and 80 mm Hg, respectively, predicted CAD risk in the population. Risk for CAD was almost twice as high in patients with BP ≥120/80 mm Hg compared with patients with a time-weighted BP <120/80 mm Hg (hazard ratio [HR], 1.9; 95% CI, 1.4 to 2.6).

Chronically elevated BP and hemoglobin A1c <8% (HR, 2.0; 95% CI, 1.06-3.9) and increased hemoglobin A1c with BP <120/80 mm Hg (HR, 1.6; 95% CI, 0.97-2.8) showed comparable magnitudes of effect on the long-term risk for CAD, indicating that BP control is similar to glycemic control in cardiovascular risk reduction.

The investigators recognized several study limitations, including its observational nature and limited available data from the time between diabetes diagnosis and study enrollment.

“These findings indicate the need for those setting treatment guidelines to consider lower BP goals [(120/80 mm Hg)] than now exist… especially for young adults with childhood-onset type 1 diabetes,” concluded the researchers.

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Guo J, Brooks MM, Muldoon MF, Naimi AI, Orchard TJ, Costacou T. Optimal blood pressure thresholds for minimal coronary artery disease risk in type 1 diabetes [published online June 27, 2019]. Diabetes Care. doi:10.2337/dc19-0480