The high prevalence of hypertension among the US black population is a major contributor to disparities in life expectancy; however, the causes for higher incidence of hypertension among black adults are unknown. A team of researchers from UAB’s School of Public Health collaborated with other organizations to evaluate potential factors associated with higher risk of incident hypertension among black adults. These UAB researchers included Drs. George Howard, Suzanne Judd, and Leann Long from the department of Biostatistics, along with Drs. Paul Muntner and Virginia Howard, from the department of Epidemiology.
Prospective cohort study of black and white adults selected from a longitudinal cohort study of 30 239 participants as not having hypertension at baseline (2003-2007) and participating in a follow-up visit 9.4 years (median) later.
There were 12 clinical and social factors, including score for the Southern diet (range, −4.5 to 8.2; higher values reflect higher level of adherence to the dietary pattern), including higher fried and related food intake. Incident hypertension (systolic blood pressure ≥140 mm Hg, diastolic blood pressure ≥90 mm Hg, or use of antihypertensive medications) at the follow-up visit.
The researchers found that of 6897 participants (mean [SD] age, 62  years; 26 percent were black adults; and 55 percent were women), 46 percent of black participants and 33 percent of white participants developed hypertension. Black men had an adjusted mean Southern diet score of 0.81 (95 percent CI, 0.72 to 0.90); white men, −0.26 (95 percent CI, −0.31 to −0.21); black women, 0.27 (95 percent CI, 0.20 to 0.33); and white women, −0.57 (95 percent CI, −0.61 to −0.54). The Southern diet score was significantly associated with incident hypertension for men (odds ratio [OR], 1.16 per 1 SD [95 percent CI, 1.06 to 1.27]; incidence of 32.4 percent at the 25th percentile and 36.1 percent at the 75th percentile; difference, 3.7 percent [95 v CI, 1.4 percent to 6.2 percent]) and women (OR, 1.17 per 1 SD [95 percent CI, 1.08 to 1.28]; incidence of 31.0 percent at the 25th percentile and 34.8 percent at the 75th percentile; difference, 3.8 percent [95 percent CI, 1.5 percent to 5.8 percent]). The Southern dietary pattern was the largest mediating factor for differences in the incidence of hypertension, accounting for 51.6 percent (95 percent CI, 18.8 percent to 84.4 percent) of the excess risk among black men and 29.2 percent (95 percent CI, 13.4 percent to 44.9 percent ) of the excess risk among black women. Among black men, a higher dietary ratio of sodium to potassium and an education level of high school graduate or less each mediated 12.3 percent of the excess risk of incident hypertension. Among black women, higher body mass index mediated 18.3 percent of the excess risk; a larger waist, 15.2 percent; less adherence to the Dietary Approaches to Stop Hypertension diet, 11.2 percent ; income level of $35 000 or less, 9.3 percent ; higher dietary ratio of sodium to potassium, 6.8 percent; and an education level of high school graduate or less, 4.1 percent.
The researchers concluded that in a mediation analysis comparing incident hypertension among black adults vs white adults in the United States, key factors statistically mediating the racial difference for both men and women included Southern diet score, dietary ratio of sodium to potassium, and education level. Among women, waist circumference and body mass index also were key factors.
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