Association of Clinical and Social Factors With Excess Hypertension Risk in Black Compared With White US Adults

Abstract

Importance: 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.

Objective: To evaluate potential factors associated with higher risk of incident hypertension among black adults.

Design, setting, and participants: 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.

Exposures: 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.

Main outcomes and measures: Incident hypertension (systolic blood pressure ≥140 mm Hg, diastolic blood pressure ≥90 mm Hg, or use of antihypertensive medications) at the follow-up visit.

Results: Of 6897 participants (mean [SD] age, 62 [8] years; 26% were black adults; and 55% were women), 46% of black participants and 33% of white participants developed hypertension. Black men had an adjusted mean Southern diet score of 0.81 (95% CI, 0.72 to 0.90); white men, -0.26 (95% CI, -0.31 to -0.21); black women, 0.27 (95% CI, 0.20 to 0.33); and white women, -0.57 (95% 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% CI, 1.06 to 1.27]; incidence of 32.4% at the 25th percentile and 36.1% at the 75th percentile; difference, 3.7% [95% CI, 1.4% to 6.2%]) and women (OR, 1.17 per 1 SD [95% CI, 1.08 to 1.28]; incidence of 31.0% at the 25th percentile and 34.8% at the 75th percentile; difference, 3.8% [95% CI, 1.5% to 5.8%]). The Southern dietary pattern was the largest mediating factor for differences in the incidence of hypertension, accounting for 51.6% (95% CI, 18.8% to 84.4%) of the excess risk among black men and 29.2% (95% CI, 13.4% to 44.9%) 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% of the excess risk of incident hypertension. Among black women, higher body mass index mediated 18.3% of the excess risk; a larger waist, 15.2%; less adherence to the Dietary Approaches to Stop Hypertension diet, 11.2%; income level of $35 000 or less, 9.3%; higher dietary ratio of sodium to potassium, 6.8%; and an education level of high school graduate or less, 4.1%.

Conclusions and relevance: 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.

Figure 1.. Flow of Participants From Baseline to the Analytic Cohort and Hypertensive Status at the Follow-up Visit

There were 130 participants excluded due to data anomalies. More than half of the study participants had hypertension at baseline and were excluded from the analysis. During the approximate 10-year follow-up, approximately 24% of the participants withdrew from the study (reflecting a 97.1% annual retention rate) and 13% to 14% died. Of those completing the second in-person examination, hypertension status could be assessed in approximately 95% of participants.

Figure 2.. Percentage of Mediation for the Excess Risk of Incident Hypertension in Black Men and Women

A 0% mediation means none of the association between race and incident hypertension is attributable to the factor (eg, the entire association between race and incident hypertension is a direct effect), whereas 100% means that race is fully mediated by the factor (eg, the total association is an indirect association with the mediating factor). There was a negative mediation for some factors (eg, for waist circumference in men). This implies that adjustment for this factor resulted in an exacerbation of the risk difference for incident hypertension with adjustment for this factor. ^aCalculated as weight in kilograms divided by height in meters squared. ^bFor men, higher waist circumference was positively associated with the risk of incident hypertension (odds ratio, 1.18 [95% CI, 1.09-1.27]; incidence proportions at 25th percentile of waist circumference of 32.5% [95% CI, 30.5%-35.0%] and at the 75th percentile of waist circumference of 36.9% [95% CI, 34.9%-39.2%]; and an absolute difference 4.4% [95% CI, 2.3%-9.2%]), but white men had a larger waist than black men; therefore, the estimated difference between black and white adults became larger when adjusted for waist circumference. ^cThe 4-item Center for Epidemiologic Studies Depression scale (CESD-4) was used; higher scores indicate more depressive symptoms. ^dHigher scores reflect more perceived stress. ^eLower scores indicate less adherence to the Dietary Approaches to Stop Hypertension (DASH) diet. ^fLower scores indicate less adherence to the Mediterranean diet. ^gHigher scores indicate more adherence to the Southern diet. ^hHigher scores indicate a greater intake of sodium relative to potassium.