Racial and Geographic Differences in Awareness, Treatment, and Control of Hypertension
The REasons for Geographic And Racial Differences in Stroke Study
Background and Purpose— Stroke mortality is higher in the “Stroke Belt” and among blacks in the United States. Because hypertension is the leading risk factor for stroke, hypertension management (raising awareness, increasing treatment, and improving control) may reduce these disparities.
Methods— Hypertension awareness, treatment, and control were measured in the REasons for Geographic And Racial Differences in Stroke study, a national population-based cohort of black and white participants >45 years of age. At the time of this report, 11 701 had been enrolled. Racial differences and geographic differences (between the Stroke Belt and other regions of the United States) were described.
Results— Black participants were more aware than whites of their hypertension (odds ratio [OR], 1.31; 95% CI, 1.07 to 1.59) and more likely to be on treatment if aware of their diagnosis (OR, 1.69; 95% CI, 1.40 to 2.05), but among those treated for hypertension, they were less likely than whites to have their blood pressure controlled (OR, 0.73; 95% CI, 0.64 to 0.83). There was no evidence of a difference between the Stroke Belt and other regions in awareness of hypertension (OR, 0.95; 95% CI, 0.79 to 1.14), but there was a trend for better treatment (OR, 1.15; 95% CI, 0.97 to 1.37) and control (OR, 1.11; 95% CI, 0.98 to 1.30) in the Stroke Belt region.
Conclusions— These findings suggest that interventions to improve blood pressure control among blacks are promising to reduce the racial disparity in stroke mortality. The lack of substantial geographic differences in hypertension awareness and the trend toward better treatment and control in the Stroke Belt suggest that differences in hypertension management may not be a major contributor to the geographic disparity in stroke mortality.
There is a higher stroke mortality rate among blacks compared with whites and in the southeastern Stroke Belt region of the United States compared with other regions (regardless of race).1 At 45 years of age, the risk of death from stroke is ≈4× greater for blacks than for whites.1–4 With increasing age, the magnitude of this disparity decreases so that by age 80, blacks and whites have a similar risk of dying of stroke.2–5 Also, residents of the southeastern United States have a 50% higher risk of dying of stroke than in other regions.6 The reasons for these racial and geographic disparities in stroke mortality are not clear.
Hypertension is the major risk factor for stroke and a major risk factor for most other cardiovascular diseases.1 The prevalence of hypertension is substantially higher in blacks,1,7,8 and there is some indication that hypertension may also be more prevalent in certain age and race groups in the southeastern United States.7,9–11 Hypertension, including inadequate control of hypertension, has been suggested as 1 of the 3 most likely causes of stroke.12 Because of the preeminence of hypertension as a stroke risk factor, we hypothesized that geographic and racial differences in awareness, treatment, and control of hypertension are major underlying contributing factors to the reported disparities in stroke mortality.
Findings from the most recent National Health and Nutrition Examination Survey (NHANES) suggested that blacks were more aware than whites of the presence of hypertension and more likely to be treated for hypertension, but among treated hypertensive participants, they were less likely to have their blood pressure adequately controlled in certain age range and ethnic/racial groups.8,13 This lower level of hypertension control may provide a promising area for intervention. The reasons for the reported racial difference in control of blood pressure are not clear.
Although the prevalence of hypertension may be higher in select age ranges for select ethnic/racial groups,1,7 to our knowledge, there are only a few reports, and nearly all use the same NHANES data that describe geographic variations in awareness, treatment, or control of hypertension.9–11 As a result, it is unclear whether hypertension management may explain the geographic disparity in stroke mortality.
In this report, we describe racial (black and white) and geographic differences in hypertension awareness, treatment, and control and attempt to determine whether observed differences could be related to racial or regional differences in demographic, socioeconomic, or other risk factor variables.
Data from the REasons for Geographic And Racial Differences in Stroke (REGARDS) were used to estimate the rates of hypertension awareness, treatment, and control in the US population of blacks and whites. REGARDS is a national population-based longitudinal cohort study. Beginning in February 2003, 30 000 individuals >45 years of age are being enrolled with equal representation of whites and blacks and men and women.14 Twenty percent of the sample is selected from the “buckle” of the Stroke Belt (coastal plain region of North Carolina, South Carolina, and Georgia), 30% from the Stroke Belt states (remainder of North Carolina, South Carolina, and Georgia, plus Alabama, Mississippi, Tennessee, Arkansas, and Louisiana), and the remaining 50% from the other 40 contiguous states. Within each region, individuals are recruited from commercially available lists of residents using a combination of mail and telephone contact. For those agreeing to participate, demographic information, medical history including previous diagnosis of high blood pressure and family history, and indices of cognitive function and quality of life are obtained by computer-assisted telephone interview. After the telephone interview, physical measures are collected at an in-home examination including blood pressure, blood and urine samples, ECG, and an inventory of current medications. Diet information (Block Food Frequency15), a residential history, and additional information is collected by self-administered questionnaires. Participants are followed by telephone at 6-month intervals for surveillance of medical events including potential stroke. The study methods were reviewed and approved by the institutional review boards at the collaborating institutions. Additional methodological details were provided previously.14
Although the recruitment goal of REGARDS is 30 000 participants, at the time of this analysis, baseline examinations were complete for the first 11 701 participants. Of these participants, 95 (0.8%) were excluded because of missing data for either blood pressure or self-reported hypertension status, resulting in an analysis cohort of 11 606 participants.
Blood pressure was taken as an average of 2 measurements taken after the participant was seated for 5 minutes measured by a trained technician using a standard protocol and regularly tested aneroid sphygmomanometer. Hypertension was defined as systolic blood pressure ≥140 mm Hg, diastolic blood pressure ≥90 mm Hg, or self-report of high blood pressure (a positive response to “Has a doctor or other health professional ever told you that you have high blood pressure?” excluding those told of hypertension only during pregnancy defined as a positive response to “Was this only when you were pregnant?” which was asked only of women). Blood pressures were obtained as part of the in-home assessment that was generally conducted within 1 month of the collection of interview data. Participants with uncontrolled hypertension were encouraged to pursue treatment following the recommendations of the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.16
Participants self-reporting hypertension were considered “aware” of the condition. Because the focus of this article was to identify opportunities to intervene to reduce the burden of stroke, we used slightly different definitions of “treatment” and “control” than previous authors (referred herein as “intervention” definitions). Participants were considered “treated” for hypertension if they responded positively to the question “Are you now taking any medicine for high blood pressure?” Participants were considered “under control” if their measured average systolic blood pressure was <140 mm Hg and diastolic blood pressure was <90 mm Hg. We define the proportion treated relative to the population that is aware of their hypertension, and likewise, we define the proportion with controlled hypertension relative to the population that is treated. We note that these “intervention” definitions differ from the “standard” definitions in which the proportion treated and the proportion controlled have been defined as a proportion of those hypertensive.
“Region” was dichotomized as residence in the Stroke Belt (including the buckle region) or the remaining 40 contiguous states.
Variables that could potentially confound the relationships between race or region with awareness, treatment, and control were categorized into 3 broad classes. Demographic variables included age, sex, and current marital status (married or not married). Socioeconomic status variables were years of education (categorized as less than high school, high school graduate, some college, or college graduate), family income (<$25 000, $25 000 to $50 000, and $50 000+), and whether the participant reported having health insurance (answering positively to “Do you have any kind of healthcare coverage such as health insurance, an HMO, or a government plan like Medicare or Medicaid?”). Risk factors considered were history of cardiovascular disease (having been told by a physician or health professional that you have had a myocardial infarction or stroke), diabetes (being told by a physician or health professional that you have diabetes), cigarette smoking (categorized as never, past, or current), or current alcohol consumption even occasionally (no/yes), body mass index (categorized as normal <24.9 kg/m2, overweight 25 to 29.9 kg/m2, or obese ≥30 kg/m2), and frequency of exercise (categorized by the question “How many times per week do you engage in intense physical activity, enough to work up a sweat?” into never, <5 times per week, and ≥5 times per week).
The same analytic approach was taken to assess racial and regional difference for each of the 3 management outcomes (aware, treated, and controlled). First, univariate analysis was conducted to show the likelihood of being aware, treated, or controlled within strata defined by race, region, demographic factors, measures of socioeconomic status, and risk factors. Logistic regression analysis was then used to estimate the odds ratio (OR) for each of the 3 outcomes in an incremental series of models that progressed from considering race and region alone to adding demographic factors, then adding socioeconomic factors, and finally adding risk factors. Because of the sampling design of REGARDS, the regional differences are reported after adjustment for race, and the racial differences are reported after adjustment for region.
Baseline demographic and risk factor characteristics are shown in Table 1. The general distribution of systolic and diastolic blood pressure is shown in Figure 1 by race and region. Systolic hypertension was common because there is a much larger proportion of patients exceeding the 160 mm Hg threshold (≈40% of blacks and 25% of whites) than the 90 mm Hg threshold (slightly >10% for blacks and slightly <10% for whites). For both the distribution of systolic and diastolic blood pressure, differences were more apparent between race groups than between regions.
Awareness of Hypertension
Of the 6023 hypertensive participants, 5477 (90.9%) were aware of the condition (Table 1; Figure 2). Although awareness of hypertension was significantly (P<0.0001) higher among blacks (92.8%) than whites (89.2%), there was no observed difference in awareness between the Stroke Belt and other regions of the United States (P=0.49). Women were more aware of hypertension than men (92.9% versus 89.6%; P<0.0001). Awareness was higher among those with lower socioeconomic status and appeared lower in association with higher levels of education and income (P=0.011 and P=0.0017, respectively). Awareness was also higher among individuals with a more adverse risk factor profile, specifically among those with diabetes (P<0.0001), history of cardiovascular disease (P<0.0001), higher body mass index (P<0.0001), nondrinkers (P<0.0001), and at lower levels of exercise (P=0.031). Awareness of hypertension was not significantly associated with age (P=0.50), cigarette smoking (P=0.17), or access to health care (P=0.068).
In multivariable modeling (Table 2), after adjustment for region, the odds were 1.45 (95% CI, 1.24 to 1.71) times greater that black participants were aware of their hypertension than whites. This increased likelihood of awareness was only slightly reduced after control for other demographic factors, measures of socioeconomic status, and other risk factors, reducing the odds to 1.31 (95% CI, 1.07 to 1.59). There was little evidence of a difference in race-adjusted awareness of hypertension between Stroke Belt and the rest of the United States (OR, 1.00; 95% CI, 0.85 to 1.18), regardless of adjustment for demographic, socioeconomic status, and risk factor variables (OR, 0.95; 95% CI, 0.79 to 1.14).
Treatment of Hypertension
Among the 6023 hypertensive individuals, 81% reported receiving treatment (“standard” coding); of the 5477 study participants aware of their hypertension, the proportion reporting receiving treatment was 88.8% (“intervention” coding; Table 1; Figure 2). Under the assumption that one must be aware of the condition to report treatment, our analyses focused on “intervention” coding for which the percentage of those treated was calculated among those who were aware of their diagnosis. In univariate analysis, this rate was higher (P<0.0001) among blacks (91.0%) compared with whites (86.7%); however, there was not a significant difference between the Stroke Belt and rest of the United States (P=0.57). The likelihood of being treated was higher with age and among those with a history of cardiovascular disease, diabetes, obesity, and was lower with cigarette smoking and alcohol drinking.
In multivariable modeling (Table 2), after adjustment for geographic region, the odds of receiving treatment among blacks with hypertension was 1.56 (95% CI, 1.34 to 1.83) times greater than among whites, a difference that was slightly accentuated by adjustment for demographic, socioeconomic, and risk factor variables, increasing to 1.69 (95% CI, 1.40 to 2.04). After adjustment for race, the odds of being treated for hypertension was ≈10% greater in the Stroke Belt compared with the rest of the United States, a difference that did not reach statistical significance (0.05<P<0.10 across 4 models considered).
Control of Hypertension
Among the 6023 hypertensive individuals, 53% reported receiving treatment (“standard” definition); of the 4858 study participants treated for their hypertension, the proportion under control was 65.8% (“intervention” definition shown in Table 1 and Figure 2). Under the assumption that one must be treated for hypertension to have the condition controlled, our analyses focused on “intervention” coding of percentages for which the percentage of those controlled was calculated as the percentage of those treated for hypertension. Adequate control was more common among whites compared with blacks (70.1% and 61.7%, respectively; P<0.0001). Of those who were treated for hypertension, the proportion whose hypertension was under control was also higher (P<0.01) among residents of the Stroke Belt (67.8%) compared with those from the rest of the United States (64.2%). The proportion with controlled hypertension was also lower at older ages and in lower socioeconomic groups (less education, lower income, or lack of health care). Control was also lower among those with an adverse risk factor profile (with diabetes, obesity, smoking, and a lower level of exercise).
In multivariate analysis (Table 2), blacks reporting treatment for hypertension had ≈30% lower odds of controlled blood pressure relative to whites (OR, 0.67; 95% CI, 0.60 to 0.74). This association was only marginally lessened after control for demographic, socioeconomic, and risk factor variables (OR, 0.73; 95% CI, 0.64 to 0.83). The odds of control among Stroke Belt residents was ≈10% greater compared with residents of other states (OR, 1.10; 95% CI, 0.99 to 1.23), a difference that approached statistical significance. This effect was largely unchanged after adjustment for demographic, socioeconomic, and risk factor variables.
We confirm previous findings of the NHANES series of reports showing a higher awareness and treatment, but poorer control, of hypertension among blacks than whites.8,10,11,13 Compared with previous reports, the adjustment for a more extensive array of factors in this report suggests that racial differences may not be explained by confounding from other identifiable factors. Although other reports from NHANES have provided estimates of geographic differences in awareness, treatment, and control of blood pressure,10–11 we updated these findings with more current data from an independently recruited study and substantially extended these analyses, providing tests of differences the significance between regions (not provided in previous reports) and by assessing the impact of confounding factors. In our data, there was little difference by region in hypertension awareness, and there was a suggestion that treatment and control of hypertension may actually be better in the Stroke Belt than the remainder of the nation. As with racial differences, regional differences were not substantially changed by adjustment for demographic, socioeconomic, or risk factor measures.
In REGARDS, the odds of hypertension awareness were ≈40% higher among blacks than whites, and the odds of receiving treatment were ≈60% higher. The odds of being aware of hypertension persisted despite adjustment for demographic, socioeconomic status, and risk factor variables, suggesting that the black–white difference in awareness and treatment is not a result of confounding from these factors but may reflect overall differences in care patterns or other factors associated with frequency of hypertension measurement or quality of hypertension care. Although improving awareness and treatment of hypertension among all populations is essential, these findings indicate that blacks are already more aware and more likely to receive treatment, but their lower level of control suggests that improving the control of hypertension among blacks is an important public health objective.
Our findings also confirm publications from the Consortium for Southeastern Hypertension Control Group, which used NHANES III data to show that, with few exceptions, there are minimal differences in awareness, treatment, and control between the southeastern United States and the remainder of the nation.10,11 In the NHANES data, hypertension awareness among black women was substantially higher in the southeastern United States (81.2% versus 74.7%), and control was substantially higher for southeastern white women (30.1% versus 26.7%) and black women (32.3% versus 24.1%) than their counterparts from the rest of the nation. These publications did not provide statistical tests for these differences, and it is possible that a relatively small sample size in these strata led to spurious differences.
Most national estimates of hypertension awareness, treatment, and control have been provided by NHANES.8–11,13 The report by Hajjar et al13 using NHANES data showed that awareness of hypertension was ≈70% and has remained constant from 1988 to 1991, through 1991 to 1994, and to 1999 to 2000 (Figure 2). Over this same period, treatment for hypertension has increased from ≈52% to 58%, and control of hypertension has increased from 25% to 31%. The recent report by Hertz et al, also based on NHANES data, used slightly different reporting intervals (1988 to 1994 versus 1999 to 2002) and focused on racial differences (Figure 2).8 In that report, the awareness of hypertension during 1988 to 1994 was slightly higher for blacks (74%) than whites (70%), it increased by 1999 to 2002 for blacks to 78%, but it remained fairly constant for whites. Treatment for hypertension was also higher for blacks (58%) than whites (54%) during 1988 to 1994 and increased substantially in both groups to 68% for blacks and 60% for whites during 1999 to 2002. Finally, based on a percentage of hypertensive individuals, Hertz et al reported lower control for blacks (23%) than whites (26%) in 1988 to 1994 and an increase in both groups during 1999 to 2002 to 32% for blacks and 35% for whites (with blacks remaining under poorer control).
Because the focus of this article was on intervention, we analyzed the “intervention” coding of percentages. To make comparisons with NHANES and Cardiovascular Health Study (CHS), which used “standard” coding, Figure 2 shows the “standard” coding of percentages in this cohort. With this “standard” analysis, of the 6023 hypertensive individuals in REGARDS, 90.9% were aware of their condition, 80.7% were treated, and 53.1% were controlled. Thus, the proportions aware, treated, and controlled were similar to CHS but still higher than NHANES (Figure 2).
In addition to the difference in the calculation of the percentages treated and controlled, there are several additional reasons for substantial differences in hypertension awareness, treatment, and control in these 3 studies. Both NHANES reports showed substantial increases in hypertension treatment and control over time,8,13 and the report of Hertz also showed increases in hypertension awareness.8 Our REGARDS cohort was recruited over the period 2003 to 2004 (primarily from 2004), and as such, a continued improvement in awareness, treatment, and control could contribute to our higher rates. In addition, different methods for identifying hypertension may contribute to the higher rates of hypertension awareness in our cohort. NHANES and CHS participants were generally evaluated at central facilities, whereas REGARDS participants were evaluated in their homes. Thus, “white-coat hypertension” may have been more likely in NHANES, leading to misclassification of individuals who did not have hypertension and underestimating the proportion aware. Julius et al reported that 7.1% of those not receiving treatment for hypertension had blood pressures >140/90 mm Hg in a clinic but had normal blood pressures in their home environment.18 Should the same mechanism be active here, ≈7% of participants would be hypertensive in NHANES who would not be hypertensive in REGARDS.
Using the “standard” coding for control as done by NHANES and CHS, 52.0% of blacks and 54.2% of whites in our study had their hypertension under control, suggesting small racial disparities in control of blood pressure. However, the “intervention” coding more clearly shows where the opportunities for intervention exist.
There are many potential reasons for poorer hypertension control in blacks. First, there may be racial differences in the aggressiveness of treatment or the quality of follow-up. For example, fewer or less effective drugs may be offered to black patients, or monitoring of treated patients may be suboptimal, leading to missed opportunities to evaluate efficacy of treatment among blacks. Second, for genetic or other reasons (related to diet, lifestyle or other factors), it is possible that specific medications are less effective in blacks than whites.12 In the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack (ALLHAT), only 60% of blacks achieved blood pressure control after 4 to 5 years of follow-up, whereas 68% of whites did, despite multiple visits, standardized protocols, and a high level of intervention.19 Third, it is possible that blacks find the side effects associated with the treatment of hypertension less acceptable. Finally, additional confounders that we have not yet considered, such as diet and stress, may explain some of the control difference between blacks and whites.
Although regional differences in the prevalence of hypertension remain a potential explanation for the increased stroke mortality in the southeastern United States, this article focuses on the awareness, treatment, and control of hypertension. In that light, in contrast to the patterns of hypertension awareness, treatment, and control among blacks and whites, we found no regional difference in blood pressure awareness and marginally significant trends for better treatment and control in the Stroke Belt that were not substantially mediated by demographic, socioeconomic status, or other risk factor variables. Thus, it is unlikely that these factors are major contributors to the reported regional disparities in stroke mortality.
The strengths and weaknesses of this study deserve mention. Our approach for blood pressure assessment could have involved any of the >6000 “field” employees of Examination Management Services, Inc. Although substantial training and standardization were made,14 these efforts cannot replicate the quality of a smaller clinic-based staff. This shortcoming is at least partially offset by the advantages of a true nationally based sample, in which participants were assessed in their homes (reducing “white-coat hypertension”). As with all epidemiologic studies, participation rates are always a concern. Because it is difficult to establish the eligibility of nonparticipants, the proportion of eligible subjects who participate is difficult to estimate. We conservatively estimated participation in the telephone interview by ≈40% of likely eligible participants contacted, which compares favorably to other epidemiologic studies. Although the previous NHANES series provide valuable historic information and although the REGARDS cohort is still being recruited, the current sample size of 11 606 is more than twice the size of the 5448 available in NHANES III,9 thus yielding more precise estimates of contemporary rates of hypertension awareness, treatment, and control. As is true in the NHANES, our population is limited to noninstitutionalized individuals; participation in REGARDS also required having a telephone, which may have further restricted representativeness of the cohort. Also, the REGARDS cohort was not designed to be representative of the US population because of oversampling of blacks and residents of the stroke belt. Like other articles examining hypertension awareness, treatment, and control, we defined “treatment” as the use of medications. It is possible that nondrug interventions (weight loss, exercise, control of sleep apnea, etc) could have been used to control blood pressure without medication. We applied traditional definitions of “treatment” as medications for several reasons; most notably, it is likely that all people who are aware of hypertension would report that they are making some effort to control the condition, albeit by minor or ineffective approaches not based on evidenced-based medicine. The vast potential for the differential impact of alternative treatments and the interaction between treatment for concomitant diseases (for example, individuals with both diabetes and hypertension therapy treated with angiotensin-converting enzyme or angiotensin receptor blocker, and combination therapy) is beyond the scope of this work. Finally, as in other observational studies, our definition of hypertension was based on measurement during a single examination and therefore may not conform to accepted diagnostic guidelines.
Overall, we report that awareness and treatment of hypertension was higher, but control of hypertension was poorer for blacks reporting hypertension treatment. This suggests that efforts to improve blood pressure control among blacks may successfully reduce racial disparities in stroke mortality. In contrast, it seems unlikely that poor awareness, treatment, and control of hypertension are major contributors to the excess stroke mortality in the Stroke Belt. Although continued emphasis on hypertension prevention, diagnosis, and management are important in all populations, additional measures may be needed to reduce the remarkable burden of the Stroke Belt.
Our findings confirm that public health efforts to educate the public about hypertension and to improve hypertension screening and detection have been largely successful, particularly among blacks. Despite this progress, there is still room for substantial improvement, and we would like to stress that these data do not indicate that the extreme diligence that has led to these improvements can be relaxed. That is, although we could not identify regional differences in hypertension awareness, treatment, and control, this does not imply that efforts should not continue to intervene at each of these stages. Likewise, although blacks are more aware and more likely to be treated than their white counterparts, this does not imply that efforts should not continue to further improve awareness and treatment in the black community, only that the allocation of resources should reflect the stage of control at which blacks are not faring as well. In that light, we hope that REGARDS will supplement and help guide the recently released and funded National Institutes of Health–National Heart, Lung, and Blood Institute initiative, “RFA HL 04-007: Interventions to Improve Hypertension Control Rates in Blacks,” that is currently under way and addressing similar issues.20 Although public health dollars must not be diverted from the goals of prevention of and screening for hypertension, our findings suggest that additional efforts focused on improving hypertension control, especially among blacks, may have a role in reducing excess stroke mortality. This study has been unable to shed any light on the role of hypertension management in explaining regional disparities in stroke mortality. However, it is clear that there is a need to increase efforts to follow through with treatment recommendations in all populations. The REGARDS study is in a unique position to evaluate directly the relationship between hypertension management and stroke incidence and mortality because of its large cohort, national sample, and longitudinal design.
The research reported in this article was supported by cooperative agreement NS 041588 from the National Institute of Neurological Disorders and Stroke.
- Received November 15, 2005.
- Revision received December 30, 2005.
- Accepted January 9, 2006.
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