Abstract MP049: Evaluating Hypertension Risk Prediction Models in Young Adults: The Coronary Artery Risk Development in Young Adults (CARDIA) Study
Authors: Carson April P , Lewis Cora E , Jacobs David R , Peralta Carmen A , Steffen Lyn M , Bower Julie K , Person Sharina D , Muntner Paul 
Published: July 2021

Background:
A hypertension risk prediction model was developed in the Framingham Heart Study (FHS), but its use among young adults has not been validated. The purpose of this study was to determine the predictive ability of the FHS hypertension model in a cohort of young adults and compare its performance with a model with pre-hypertension as the only predictor.

Methods:
This study included 4453 participants, aged 18–30 years at enrollment, from the Coronary Artery Risk Development in Young Adults (CARDIA) Study who attended 2 consecutive exams between the baseline (1985-86) and seventh examinations (2005–06). Data were pooled such that the interval between any 2 consecutive exams was 1 time period (median=2.9 years); participants contributed up to 6 time periods at risk for hypertension. Participants with prevalent hypertension or diabetes at the start of each risk period were excluded from that and subsequent risk periods. The FHS hypertension model includes the following variables: age, sex, systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index, parental hypertension, current smoking, and an age-DBP interaction term at the baseline for each risk period. Incident hypertension was defined as SBP≥140 mmHg, DBP≥ 90 mmHg, or new use of antihypertensive medications. Pre-hypertension was defined as 120≤SBP≤139 mmHg or 80≤SBP≤89 among those not meeting hypertension criteria. The c-statistic was used to assess model discrimination and the Hosmer-Lemeshow chi-square statistic was used to assess model calibration based on quintiles of risk for hypertension.

Results:
The crude hypertension incidence rate was 13.2 per 1,000 person-years. The FHS hypertension model performed well in identifying those who did and did not develop hypertension (c-statistic=0.87, 95% CI=0.86, 0.88) and was better than a model with pre-hypertension as the only predictor (c-statistic=0.73, 95% CI=0.71, 0.75). The predicted risk from the FHS hypertension model was systematically lower than the observed hypertension incidence in each quintile (Hosmer-Lemeshow χ2= 2649.35; p<0.001). Using CARDIA’s hypertension incidence rate and mean levels of its risk factors to recalibrate the model, the differences between predicted risk and observed hypertension incidence improved but the predicted risk overestimated observed risk in the bottom 4 quintiles and underestimated observed risk in the top quintile (Hosmer-Lemeshow χ2= 47.31; p<0.001).

Conclusions:
The FHS model performed well in identifying those who developed hypertension in this cohort study of young adults. This model performed better than a pre-hypertension only model, but calibration was poor. The FHS hypertension model may be a useful tool for discriminating individuals with and without a high risk for hypertension and could lead to improvements in targeted prevention strategies for young adults.