Higher incidence among blacks also associated with other social, clinical factors
Several clinical and social factors have contributed to the higher rates of hypertension among black American adults, but key among them is the "Southern diet," a prospective cohort study found.
Such a diet -- calorie-dense with relatively little fresh fruit and vegetables or whole grains -- was the largest statistical mediator of difference in hypertension prevalence between black and whites, accounting for 29.2% of the excess risk among black women and 51.6% of the excess risk among black men, reported George Howard, DrPH, of the University of Alabama at Birmingham, and colleagues in JAMA.
The researchers found a greater number of significant mediating factors among women than men for the racial disparity in hypertension incidence, which "may be partially attributable to an observed stronger association of race with incident hypertension among women than men that would provide greater statistical power to detect mediating factors," they wrote.
This study provided a look into "some of the unique lifestyle choices that individuals make in terms of diet and exercise and other factors that may be contributing to a more likely development of hypertension and as such it is a non-biased assessment of diet and exercise and alcohol and smoking and all the other factors that we presume contribute to hypertension," commented Donald Molony, MD, of University of Texas Health Science Center in Houston, in an interview with MedPage Today.
The researchers evaluated 6,897 participants (mean age 62), among whom 26% were black and 55% were women. Over the course of the study, 46% of black participants and 33% of white participants developed hypertension in a follow-up visit 9.4 years later.
Black participants scored higher on the adjusted mean Southern diet scale, which ranges from -4.5 to 8.2 and where higher values are associated with higher intake of fried foods, organ meats, processed meats, eggs, added fats, high-fat dairy, sugar-sweetened beverages, and bread. The researchers found the following average scores:
- Black men: 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)
- White women: -0.57 (95% CI, -0.61 to -0.54)
Higher Southern diet scores were significantly linked with incident hypertension for women (OR 1.17 per 1 SD; 95% CI, 1.08-1.28) and for men (1.16 per 1 SD; 95% CI, 1.06 to 1.27).
Among black men, two other factors were significant -- a higher dietary ratio of sodium to potassium and an educational level of graduating high school or even less each accounted for 12.3% of the excess hypertension risk compared with white men.
Among black women, the proportion of excess risk mediated by the various risk factors was:
- 18.3% for higher body mass index
- 15.2% for a larger waist
- 11.2% for lower adherence to the Dietary Approaches to Stop Hypertension (DASH) diet
- 9.3% for income level of $35,000 or less
- 6.8% for higher dietary ratio of sodium to potassium
- 4.1% for education level of high school graduate or less
Comment on the study's findings, Molony noted that there was "little evidence from this cohort that alcohol consumption and lifestyle stresses are contributing significantly to hypertension."
Perceived stress levels reported by the participants were similar between black and white groups by gender.
However, Molony questioned that finding. "I'm concerned about the stress issue, because I don't think that the measurements that they used are sensitive enough to look at daily stresses on the development of hypertension. More importantly, if stress is a factor in the development of hypertension in the African American population, then it might be more important in the younger age groups that are excluded from the study," Molony continued.
The researchers acknowledged the limitations of their work: over half of the cohort did not have a follow-up visit, 16% passed away, and 24% did not complete the study because they withdrew or declined follow-up.
The investigators also noted the potential for measurement error and misclassification of mediating factors. "Such misclassification would generally lead to underestimation of the effects of potential mediating factors, so the reported estimates of the mediating effects could be underestimates," the investigators wrote.
The study was funded by the National Institute of Neurological Disorders and Stroke.
Howard and Molony did not disclose any relevant financial relationships with industry.
Source Reference: Howard G, et al “Association of clinical and social factors with excess hypertension risk in black compared with white US adults” JAMA 2018; DOI: 10.1001/jama.2018.13467.
Read the original article on Medpage Today: Southern Diet Called Single Biggest Factor in HTN Racial Disparities