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Are there factors that may mediate the higher incidence of hypertension among black adults compared with white adults?
In this mediation analysis that included 6897 adults who participated in a follow-up visit 9.4 years (median) later, the largest statistical mediator of the difference in hypertension incidence between black and white participants was the Southern dietary pattern, accounting for 51.6% of the excess risk among black men and 29.2% of the excess risk among black women.
These findings may provide insights into the sources of racial disparities in hypertension incidence.
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.
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.
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.
Of 6897 participants (mean [SD] age, 62  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.
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Corresponding Author: George Howard, DrPH, Department of Biostatistics, University of Alabama at Birmingham, 1665 University Blvd, Birmingham, AL 35294 (firstname.lastname@example.org).
Accepted for Publication: August 21, 2018.
Correction: This article was corrected on October 8, 2018, to remove the comma after “Alabama” and add the word “at” so that it appears as “University of Alabama at Birmingham.”
Author Contributions: Dr G. Howard had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: G. Howard, Cushman, Moy, Oparil, Lackland, Judd, Long, V. Howard.
Acquisition, analysis, or interpretation of data: G. Howard, Cushman, Muntner, Lackland, Manly, Flaherty, Judd, Wadley, Long, V. Howard.
Drafting of the manuscript: G. Howard, Long.
Critical revision of the manuscript for important intellectual content: Cushman, Moy, Oparil, Muntner, Lackland, Manly, Flaherty, Judd, Wadley, Long, V. Howard.
Statistical analysis: G. Howard, Lackland, Long.
Obtained funding: G. Howard, Cushman, Manly, V. Howard.
Administrative, technical, or material support: G. Howard, Cushman, Muntner, Manly, Judd, V. Howard.
Supervision: G. Howard, Oparil, V. Howard.
Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Oparil reported receiving grant support from Actelion, Novartis, and Bayer Healthcare Pharmaceuticals; receiving personal fees from Boehringer-Ingelheim, Lilly, George Clinical Pty Ltd/Actelion Clinical Research Inc, Lundbeck, Novo Nordisk, ROX Medical, and 98point6; and serving as editor in chief for Current Hypertension Reports. Dr Muntner reported receiving grant support from the National Institutes of Health and the American Heart Association; and receiving grant support and personal fees from Amgen. Dr Manly reported receiving grant support from the National Institutes of Health and the National Institute on Aging. No other disclosures were reported.
Funding/Support: The REGARDS study was funded through cooperative agreement U01-NS041588 from the National Institute of Neurological Disorders and Stroke (NINDS). Dr Moy (an NINDS employee) participated as an equal voting member of the study executive committee since the study’s initiation.
Role of the Funder/Sponsor: Dr Moy (an NINDS employee) had a role in the design and conduct of the study; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication; but did not participate in the collection, management, analysis, and interpretation of the data.
Data Sharing Statement: See Supplement 2.
Additonal Contributions: We thank the investigators, staff, and participants of the REGARDS study for their valuable contributions. A full list of participating REGARDS investigators and institutions can be found at http://www.regardsstudy.org.
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