Factor IX and incident hypertension in Black and White adults: the REasons for Geographic and Racial Differences in Stroke cohort.

Background: Hypertension is a cardiovascular disease risk factor disproportionately affecting Black adults. Certain biomarkers of thrombosis and inflammation are associated with a greater risk of hypertension. Factor IX is a marker of thrombosis; Black adults have higher levels than others. Whether factor IX correlates with incident hypertension risk or explains some of the disproportionate burden faced by Black adults, is not known.

Methods: REasons for Geographic and Racial Differences in Stroke (REGARDS) recruited 30 239 Black and White adults from the contiguous US in 2003-2007 (Visit 1) and had repeat assessment in 2013-2016 (Visit 2). Factor IX was measured in Visit 1 samples in a sex-race stratified sample of 4400 participants that attended both visits. Modified Poisson regression estimated adjusted risk ratios (RR) for incident hypertension at Visit 2 by factor IX tertiles. Inverse odds ratio weighting estimated the proportion of the excess burden of incident hypertension in Black adults due to factor IX levels.

Results: Among 1824 participants (55% female and 24% Black race), 36% developed hypertension. The fully adjusted RR for the third vs. first tertile was 1.21; 95% confidence interval (CI) 1.03-1.43, and there was a significant linear trend across tertiles (P < 0.001). Factor IX did not mediate excess hypertension risk among Black adults in adjusted models.

Conclusions: In this prospective study of Black and White adults without prevalent hypertension, higher factor IX was associated with a greater risk of incident hypertension. This risk may relate to adverse thromboinflammation among persons in the 2nd and 3rd tertiles of factor IX.