Research Article
Prevalence of hypertension by duration and age at exposure to the stroke belt

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Abstract

Geographic variation in hypertension is hypothesized as contributing to the stroke belt, an area in the southeastern United States with high stroke mortality. No study has examined hypertension by lifetime exposure to the stroke belt. This association was studied in 19,385 participants in the REasons for Geographic And Racial Differences in Stroke (REGARDS) study, a national population-based cohort. Prevalent hypertension was defined as systolic blood pressure ≥140, diastolic blood pressure ≥90, or use of antihypertensive medications. Stroke belt exposure was assessed by residence at birth, currently, early childhood, adolescence, early adulthood, mid-adulthood, and recently. After adjustment for age, race, sex, physical activity level, body mass index, smoking, alcohol, education, and income, the prevalence of hypertension was significantly more strongly related (P < .0001) with lifetime exposure, adolescence, or early adulthood exposure than exposures at other times. Birthplace and current residence were independently associated with hypertension; however, lifetime, adolescence, or early adulthood exposures were more predictive than joint model with both birthplace and current residence. That adolescence and early adulthood periods are more predictive than residence in the stroke belt for most recent 20-year period suggests community and environmental strategies to prevent hypertension need to start earlier in life.

Introduction

The US stroke belt, usually defined as including the eight southern states of North Carolina, South Carolina, Georgia, Tennessee, Mississippi, Alabama, Louisiana, and Arkansas, was first identified in 1965 with approximately a 50% higher stroke mortality then the rest of the country, and it still persists today.1, 2, 3, 4, 5, 6 Within the stroke belt, a “buckle” region along the coastal plain of North Carolina, South Carolina, and Georgia has been identified with even a higher stroke mortality rate than the remainder of the stroke belt.7 Higher prevalence of hypertension has been hypothesized as one of the causes of the higher stroke mortality rates in the southeastern US stroke belt.6, 8, 9 In studies of regional comparisons of hypertension prevalence, a slightly higher prevalence of hypertension in the southeast was found for some race-sex groups (white men, white women, and black men) with a more substantial difference for black women.10, 11 In further analysis assessing age groups, in seven of eight age-race-sex strata, hypertension was more prevalent in the southeast, but the regional differences were only statistically significant among black men ages 40 to 59 and white men ages 40 to 59.9 Cross-sectional analysis of the Framingham Stroke Risk Score from the REasons for Geographic And Racial Differences in Stroke (REGARDS) national cohort study found that use of antihypertensive medications was more common in the stroke belt than the rest of the nation for both blacks and whites, but the pattern of systolic blood pressures (SBP) was not consistent: whites in the stroke belt (but not the buckle) had higher SBP than the rest of the nation and blacks in the stroke buckle (but not the belt) had lower SBP than rest of nation.12

Previous studies have shown that nativity or birthplace is associated with cardiovascular mortality, with individuals born in the Southeast having higher rates than those born in other regions of the United States.13, 14 These studies, however, did not assess the relationship of birthplace or extent of lifetime exposure in the stroke belt to blood pressure or hypertension. Studies in other countries have examined blood pressure measurements and other cardiovascular risk factors by birthplace and region of residence in childhood and adulthood and conclude that current residence is more influential than region of birth.15, 16 These studies, however, have focused on only a few residency periods. We use lifetime residential history data from a US adult cohort to examine the prevalence of hypertension by exposure to the stroke belt at birth, current residence, and six other measures of lifetime exposure to the stroke belt.

Section snippets

Methods

This report uses cross-sectional data from REGARDS, a longitudinal population-based cohort study designed to investigate factors associated with the excess stroke mortality observed among African Americans and residents of the southeastern United States.17 REGARDS was designed to be a national cohort of community-dwelling individuals age 45 years and older, randomly selected with approximately equal representation of whites and blacks, men and women, with oversampling from the stroke belt.

Results

Table 1 shows the baseline characteristics by region and by race-sex group within region. Thirty-eight percent (7,224) of the participants were African American, 54.3% (10,239) were women, and 53% (10,006) resided in the stroke belt at the time of the home examination. The mean (SD) age was 66.1 (9.0) with a range of 45 to 96 years. There were 11,247 participants (58.0%) with prevalent hypertension. Overall, blacks had higher prevalence of hypertension than whites did: 73.0% of black females,

Discussion

Our study shows that exposure to the stroke belt is associated with higher prevalence of hypertension among a national sample of adults age 45 and older. After adjustment for age, race, sex, physical activity level, BMI, smoking, alcohol use, education, and income, the prevalence of hypertension was significantly most strongly related (P < .0001) to lifetime as well as adolescence or early adulthood exposure to the stroke belt than exposures at other times. Birthplace and current residence in

Acknowledgments

The authors acknowledge the participating investigators and institutions for their valuable contributions: The University of Alabama at Birmingham, Birmingham, AL (Study PI, Statistical and Data Coordinating Center, Survey Research Unit): George Howard, DrPH, Leslie McClure, PhD, Virginia Howard, PhD, Libby Wagner, MA, Virginia Wadley, PhD, Rodney Go, PhD, Monika Safford, MD, Ella Temple, PhD, Margaret Stewart, MSPH; University of Vermont (Central Laboratory): Mary Cushman, MD; Wake Forest

References (35)

  • G. Howard et al.

    Evaluation of social status as a contributing factor to the stroke belt region of the United States

    Stroke

    (1997)
  • T.O. Obisesan et al.

    Geographic variation in stroke risk in the United States. Region, urbanization, and hypertension in the Third National Health and Nutrition Examination Survey

    Stroke

    (2000)
  • W.D. Hall et al.

    Hypertension-related morbidity and mortality in the southeastern United States

    Am J Med Sci.

    (1997)
  • D. Jones et al.

    Managing hypertension in the southeastern United States: applying the guidelines from the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI)

    Am J Med Sci.

    (1999)
  • M. Cushman et al.

    Estimated 10-year stroke risk by region and race in the United States: geographic and racial differences in stroke risk

    Ann Neurol

    (2008)
  • D.T. Lackland et al.

    Impact of nativity and race on "Stroke Belt" mortality

    Hypertension

    (1999)
  • J. Fang et al.

    The association between birthplace and mortality from cardiovascular causes among black and white residents of New York City

    N Engl J Med

    (1996)
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    The REGARDS research project is supported by a cooperative agreement U01 NS041588 from the United States National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services. This work was also supported in part by the Black Pooling Project funded by the United States National Heart Lung and Blood Institute grant 1R01HL072377.

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