Sex, adiposity, and hypertension status modify the inverse effect of marine food intake on blood pressure in Alaska Native (Yup'ik) people

Background: Alaska Native people currently have a higher prevalence of hypertension than do nonnative Alaskans, although in the 1950s hypertension was rare among Alaska Native people. A novel biomarker of marine foods, the nitrogen isotope ratio (δ¹⁵N) in RBCs was shown to be negatively associated with systolic and diastolic blood pressure. Few studies have examined how individual characteristics modify the association of marine food intake with blood pressure. Objective: This exploratory analysis examined whether sex, adiposity, and hypertension modify the inverse association between marine food intake and blood pressure. Methods: We used covariate-adjusted linear models to describe the association between δ¹⁵N and blood pressure in 873 adult Alaska Native (Yup'ik) people who resided in 8 communities in southwest Alaska. We separately stratified by sex, body mass index (BMI) group, abdominal obesity, and hypertension status and assessed the interaction between δ¹⁵N and participant characteristics on blood pressure via likelihood ratio tests. Results: The association between δ¹⁵N and systolic blood pressurewas modified by sex, BMI status, and abdominal obesity, with the inverse association observed only in the male (β = 21.5; 95% CI: 22.4, 20.6), nonobese BMI (β = 21.7; 95% CI: 22.5, 21.0), and non-abdominally obese (β = 21.6; 95% CI: 22.4, 20.9) strata (all P-interaction < 0.0001). A reduction in diastolic blood pressure associated with δ¹⁵N was observed in the nonobese BMI ((β = 21.1; 95%CI: 21.7, 20.5) and non- abdominally obese (β = 21.1; 95% CI: 21.7, 20.5) strata, although only the interaction between BMI group and δ¹⁵N with diastolic blood pressure was significant. The inverse association between δ¹⁵N and both systolic and diastolic blood pressure was observed in nonhypertensive individuals, although the comparison had limited power. The results were consistent with those identified by using combined RBC concentrations of eicosapentaenoic acid and docosahexaenoic acid as the biomarker of marine food intake, although the associations identified by using δ¹⁵N were larger. Conclusions: Obesity status modified the inverse association between marine food intake and both systolic and diastolic blood pressure in adult Alaska Native (Yup'ik) people. The inverse association between δ¹⁵N and systolic blood pressure was also modified by sex.