Research paper Blacks managing high blood pressure while maintaining a quality lifestyle

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Racial Disparity in Hypertension Control:

Tallying the Death Toll

ABSTRACT PURPOSE Black Americans with hypertension have poorer blood pressure control than their white counterparts, but the impact of this disparity on mortality among black adults is not known. We assessed differences in systolic blood pressure (SBP) control among white and black adults with a diagnosis of hypertension, and mea- sured the impact of that difference on cardiovascular and cerebrovascular mortality among blacks.

METHODS Using SBP measurements from white and black adults participating in the National Health and Nutrition Examination Survey, 1999-2002, we modeled changes in mortality rates resulting from a reduction of mean SBP among blacks to that of whites. Our data source for mortality estimates of blacks with hyper- tension was a meta-analysis of observational studies of SBP; our data source for reduction in mortality rates was a meta-analysis of SBP treatment trials.

RESULTS The fi nal sample of participants for whom SBP measurements were available included 1,545 black adults and 1,335 white adults. The mean SBP among blacks with hypertension was approximately 6 mm Hg higher than that for the total adult black population and 7 mm Hg higher than that for whites with hypertension. Within the hypertensive population, a reduction in mean SBP among blacks to that of whites would reduce the annual number of deaths among blacks from heart disease by 5,480 and from stroke by 2,190.

CONCLUSIONS Eliminating racial disparity in blood pressure control among adults with hypertension would substantially reduce the number of deaths among blacks from both heart disease and stroke. Primary care clinicians should be particularly diligent when managing hypertension in black patients.

Ann Fam Med 2008;6:497-502. DOI: 10.1370/afm.873.

INTRODUCTION

C ardiovascular disease, the leading cause of death in the United

States, occurs at the highest rate among black Americans.1 As a

precursor to cardiovascular disease, hypertension is one of the

most important contributors to racial disparities in mortality rate.2 The

age-adjusted prevalence of hypertension is signifi cantly higher among

blacks (39%) than among whites (29%).3 Uncontrolled hypertension has

an enormous impact on the health of minorities,1,4 accounting for up to

one-quarter of all deaths among black adults, primarily from cardiovascu-

lar and cerebrovascular causes.5

Recent data suggest that among persons under treatment for hyperten-

sion, blacks have poorer blood pressure control.3 Only a few studies have

quantifi ed the effects of racial disparities in health care interventions on

the number of deaths among.6,7 To our knowledge, none have quantifi ed

the impact of disparity in hypertension control on black mortality.

To model the impact of this disparity in hypertension control, we

used national data on systolic blood pressure (SBP), mortality data, and

published estimates of the relative risk associated with decreases in SBP.

Specifi cally, we calculated the annual numbers of heart and stroke deaths

Kevin Fiscella, MD, MPH1,2

Kathleen Holt, PhD1

1Department of Family Medicine, Univer-

sity of Rochester School of Medicine and

Dentistry, Rochester, New York

2Department of Community and Preven-

tive Medicine, University of Rochester

School of Medicine and Dentistry, Roch-

ester, New York

Confl icts of interest: none reported

CORRESPONDING AUTHOR

Kevin Fiscella, MD, MPH

Departments of Family Medicine,

and Community and Preventive Medicine

University of Rochester School

of Medicine and Dentistry

1381 South Ave

Rochester, NY 14620

[email protected]

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that would be avoided or postponed assuming blacks

with hypertension had their blood pressure controlled

to the same level as whites.

METHODS Data Sources We used SBP data from the National Health and

Nutrition Examination Survey (NHANES) for the

years 1999-2002. NHANES is a periodic national

survey of the health status of the United States and is

designed to yield nationally representative estimates.

It includes data from questionnaires, physical examina-

tions, and medical tests. Eligibility criteria for our sam-

ple included (1) self-identifi cation as white or black, (2)

age of 25 years or older, and (3) diagnosis of hyperten-

sion (regardless if treated or not). We also used 2002

US black mortality data for heart disease and stroke,

stratifi ed by sex and age.8

We estimated the additional risk associated with

an elevated SBP based on a meta-analysis of epidemio-

logic studies of SBP and mortality. This meta-analysis,

based on approximately 1 million individuals, estimated

the risks, stratifi ed by age and sex, of heart disease

and stroke associated with elevated blood pressure.9

We estimated the effect of reductions in SBP based

on relative risks for heart disease and stroke mortality

from a meta-analysis of randomized treatment trials of

hypertension.10

Estimating Black Mortality Risk From Hypertension National mortality rates are known for all black adults

(ie, those with and without hypertension), but not for

black adults with hypertension. To estimate sex- and

age- specifi c mortality rates for this group, we used

NHANES data to derive the mean difference in SBP

between blacks with hypertension and all blacks by sex

and age. Next, we calculated the relative risk associ-

ated with a given difference in SBP between blacks

with hypertension and all blacks using the following

sex- and age-specifi c exponential function, derived

from a meta-analysis of observational studies of blood

pressure and mortality9:

RR = RRs (ΔSBP/20)

where ΔSBP equals the difference in mean SBP

between blacks with a hypertension diagnosis and

all blacks aged 25 years or older, and RRs equals the

relative risk for heart disease or stroke by age and sex

for a standardized ΔSBP of 20 mm Hg. The relative

risk was then applied to each sex and age category for

heart disease and stroke mortality to produce mortality

rates adjusted for hypertension. For example, the dif-

ference in mean SBP among black men aged 55 to 64

years with hypertension relative to all black men in this

age category was 5 mm Hg (142 vs 137 mm Hg). This

difference represents a relative risk for heart disease

mortality of 1.17 (1/0.53 (5/20)). The overall mortality

rate for black men in this age-group is 605 deaths per

100,000. Among black men of this age with hyperten-

sion, the overall mortality is thus estimated at 708 per

100,000 (605 × 1.17). This estimate is conservative because it does not adjust for comorbidity (such as

diabetes, hyperlipidemia, or obesity) associated with

hypertension.11

Estimating Relative Risk From Disparity in SBP We estimated the relative risk associated with racial dis-

parity in SBP based on a reduction in the mean SBP for

blacks to that of whites in the same sex and age group.

We calculated the mean difference in SBP between

blacks and whites for each group using NHANES

data and used a relative risk for reduction in SBP from

a meta-analysis of randomized trials of hypertension

treatment.10 In that meta-analysis, an 8.3-mm Hg reduc-

tion in SBP was associated with a relative risk of 0.80

(95% confi dence interval [CI], 0.77-0.84) for heart

disease mortality and a relative risk of 0.67 (95% CI,

0.61-0.74) for stroke mortality. We then estimated the

relative risk in heart disease mortality for various reduc-

tions in SBP using the following formula:

RR = RRs Δ SBP/8.3

where ΔSBP equals the difference in SBP between

blacks and whites matched for sex and age based on

NHANES data, and RRs is the relative risk for heart

disease or stroke standardized to an 8.3-mm Hg

decrease in SBP. We then converted relative risks to

relative risk reductions (RRR = 1 – RR).

Estimating Deaths From Disparity in SBP To estimate the number of deaths among blacks that

would be postponed or avoided if parity in SBP control

were achieved, we multiplied the relative risk reduc-

tion by the sex- and age-specifi c mortality rates (AMR)

for blacks adjusted for SBP to obtain the absolute risk

reduction. We then multiplied this by the estimated

number of blacks (N) in each sex and age group,

derived from NHANES data. Our estimate for deaths

was thus equal to RRR × AMR × N.

Statistical Analyses The number of persons in each sex and age group and

mean SBPs for blacks and whites were derived from

NHANES data, weighted to yield national estimates

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using SAS (SAS Institute Inc, Cary, North Carolina).

All other calculations were performed using Microsoft

Excel (Microsoft Corp, Redmond, Washington).

Sensitivity Analyses We conducted a series of sensitivity analyses around

key estimates in the model. First, we assessed the effect

of assuming a ±30% black-white difference in SBP.

We also assumed a constant difference in SBP across

all age-groups using the mean SBP by sex to assess

the effect of age distributions on our fi ndings. Next,

we used the 95% CIs surrounding the estimated rela-

tives risks associated with decreases in SBP.10 Last, we

assumed comparable risk per change in SBP regardless

of the source of the estimate, for example, observa-

tional data vs treatment data.10

RESULTS There were 661 black adults and 1,335 white adults

with hypertension in the sample and an additional

884 blacks without hypertension. Table 1 shows the

number of black men and women in the sample with

hypertension in each age-group along with their mean

SBP and corresponding 95% CIs. For men, the mean

SBP was 22 mm Hg higher in the oldest as compared

with the youngest cohort. For women, that difference

was 26 mm Hg.

The differences in mean SBP by age and sex among

blacks with hypertension, the entire black adult popu-

lation, and non-Hispanic whites with hypertension are

shown in Table 2. The mean SBP among black men

with hypertension was 6 mm Hg higher than that for

all black men and 6.5 mm Hg higher than that for

white men with hypertension. For women, the differ-

ences were 6.5 and 8.2 mm Hg, respectively.

Table 3 shows the annual mortality rates by age

and sex for heart disease and stroke for the entire black

population, estimates of annual mortality rates for

those with hypertension, and estimates for blacks with

hypertension assuming racial parity in blood pressure

control. Parity in SBP control would reduce annual

mortality rates from heart disease and stroke among

men by 17% and 16%, respectively. For women, the

reductions would be smaller, 9% and 14%, respectively.

Racial parity in hypertension control would reduce

the annual number of deaths from heart disease and

stroke by an estimated 5,480 and 2,190 (Table 4). Sen-

sitivity analyses are shown in the Supplemental Appen-

dix (available online at http://www.annfammed.

org/cgi/content/full/6/6/497/DC1). Use of 30%

lower or higher estimates for racial differences in

SBP yielded a 23% to 28% variation in death estimates.

Use of a constant (mean SBP difference by race) across

age-groups yielded slightly lower estimates for men,

but substantially higher estimates for women relative to

the base case. In general, use of a constant difference

Table 1. Mean Systolic Blood Pressures of Blacks With Hypertension by Age and Sex, United States, NHANES 1999-2002

Age-Group, Years

US Population 2002

Mean Systolic Blood Pressure (95% CI),

mm Hg

Men 25-34 2,537,000 128 (121-135) 35-44 2,681,000 135 (130-141) 45-54 2,116,000 138 (133-143) 55-64 1,116,000 142 (136-148) 65-74 693,000 139 (138-144) ≥75 436,000 150 (141-159)

Women

25-34 2,792,000 126 (121-130) 35-44 3,024,000 135 (130-141) 45-54 2,460,000 142 (136-147) 55-64 1,438,000 141 (136-146) 65-74 977,000 148 (142-153) ≥75 849,000 152 (145-159)

NHANES = National Health and Nutrition Examination Survey; CI = confi dence interval.

Table 2. Differences in Mean Systolic Blood Pressures by Age and Sex Between Blacks With Hypertension vs the Black Population and vs Non-Hispanic Whites With Hypertension

Group

Difference in Systolic Blood Pressure, mm Hg

Blacks With Hypertension vs Entire Black

Population

Blacks With Hypertension

vs Whites With Hypertension

Men Age-group, years

25-34 8 1 35-44 9 7 45-54 7 9 55-64 5 10 65-74 1 3 ≥75 6 9

Unweighted mean Δ 6.0 6.5

Women Age-group, years

25-34 12 14 35-44 13 13 45-54 12 10 55-64 3 4 65-74 1 4 ≥75 2 1

Unweighted mean Δ 6.5 8.2

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in SBP increased the number of deaths

from heart disease by 43% and that

from stroke by 49%. Use of the 95%

upper and lower CIs yielded roughly

8% to 15% variations in estimates for

heart disease deaths and 18% to 22%

variations in those for stroke deaths.

Last, substitution of age- and sex-spe-

cifi c relative risk values from observa-

tional studies for those from treatment

studies yielded a 9% higher estimate

of deaths from heart disease and a 21%

lower estimate of deaths from stroke

relative to the base case, but very simi-

lar estimates of death from heart disease

and stroke combined (7,670 vs 7,720).

DISCUSSION Our fi ndings show that racial disparity

in SBP control contributes to nearly

8,000 excess deaths annually from

heart disease and stroke among blacks.

These fi ndings are fairly robust to

changes in key model assumptions. Pre-

vious analyses have shown that hyper-

tension is the single largest contributor,

of any medical condition, to racial disparity in adult

mortality.2 This excess mortality results from a com-

bination of a higher age-adjusted prevalence of hyper-

tension and poorer control of blood pressure among

those under treatment.3 Our analysis estimated the

contribution of just the latter factor to deaths among

blacks, but nonetheless, found a substantial impact on

the number of deaths in this racial group.

To our knowledge, this study represents the fi rst

effort to quantify the toll of racial disparities in blood

pressure control. Given the high prevalence of hyper-

tension in blacks, appreciable benefi ts of blood pres-

sure reduction, and signifi cant disparity in control, it is

not surprising that disparity in blood pressure control

results in appreciably more deaths than those estimated

from other health care disparities, including infl uenza

vaccination, mammography screening, use of β-block- ers after myocardial infarction, treatment of childhood

asthma, and diabetes.6,7

The causes of racial disparity in blood pressure

control are not known.12 There are several potential

explanations—differences in access to care, clini-

cian management, hypertension severity, and patient

adherence. Surprisingly, NHANES data show no

racial difference in treatment among all patients with

hypertension, suggesting that rates of diagnosis and

treatment among blacks in this sample are the same

Table 3. Black Mortality Rates by Age, Sex, and Blood Pressure

Group

Entire Black Populationa

Black Adults With

Hypertensionb

With Racial Parity in Blood

Pressure Controlb

Heart Disease Stroke

Heart Disease Stroke

Heart Disease Stroke

Men

Age-group, years 25-34 65 12 85 19 83 19

35-44 107 20 146 33 121 24

45-54 246 47 314 69 246 44

55-64 605 110 709 141 542 87

65-74 1,192 262 1,225 273 1,130 236

≥75 3,556 864 4,047 1,017 3,177 659

Age adjusted 419 90 733 167 603 140

Women

Age-group, years

25-34 24 7 39 11 7 6

35-44 58 17 98 28 89 15

45-54 125 36 186 54 142 33

55-64 312 70 334 75 277 54

65-74 734 181 758 187 680 154

≥75 3,438 975 3,527 1,000 3,433 953

Age adjusted 400 109 589 159 538 136

Note: mortality rates are expressed as number of deaths per 100,000.

a Data from Kochanek and Smith.8 b Derived estimates. See Methods for calculation details.

Table 4. Annual Deaths From Heart Disease and Stroke Avoided or Postponed Among Blacks Through Parity in Blood Pressure Control Between Black and White Adults With Hypertension, by Age and Sex

Group

Annual No. of Deathsa

Heart Disease Stroke

Men Age-group, years

25-34 10 0 35-44 120 50 45-54 480 170 55-64 940 300 65-74 420 160 ≥75 1,450 600

Overall 3,420 1,280

Women

Age-group, years

25-34 50 20 35-44 230 110 45-54 420 200 55-64 560 210 65-74 440 190 ≥75 360 180

Overall 2,060 910 Men and women 5,480 2,190

a Derived estimates. See Methods for calculation details.

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as among whites.3 Although there is considerable

evidence for racial disparity in management of car-

diovascular disease,13 there is little evidence of racial

disparity in treatment of hypertension. Specifi cally,

among those with hypertension, there is no signifi cant

difference in rates of drug treatment of hypertension

by race.12 In addition, some data suggest no difference

in clinician adherence to national hypertension treat-

ment guidelines or intensifi cation of antihypertensive

treatment by race.14

It is possible that blacks have more severe hyper-

tension or respond less favorably to antihypertensive

drugs. There is no clear evidence, however, for racial

differences in severity, and meta-analyses of treatment

trials show a similar response to antihypertensive medi-

cation by race, with whites having a slightly greater

response to β-blockers and blacks having a slightly greater response to diuretics.15

There is evidence for racial disparity in patient

adherence to antihypertensive medication, including

studies conducted within the Veterans Administra-

tion Health System, where fewer differences in access

appear to exist.16-18 Differences in adherence by race

may be due to affordability of medicines, personal

beliefs, anticipated adverse effects, and health literacy

that disproportionately affect blacks.18-20

Although multiple causes may contribute to racial

disparity in blood pressure control, this disparity is

not inevitable. Disparity in hypertension control is

signifi cantly smaller in the Veterans Administration

Health System, where access barriers are fewer.21 Little

or no disparity in blood pressure control was noted in

the treatment arms of 2 large community-based hyper-

tension treatment trials, the Hypertension Detection

and Follow-up Program and the Multiple Risk Factor

Intervention Trial.22,23 It is thus probable that elimina-

tion of racial disparity in SBP is an attainable goal, pro-

vided suffi cient resources are available to discover and

address adherence barriers.

The strengths of this study include use of a nation-

ally representative sample to estimate blood pressures

among persons with hypertension; use of race-, sex-,

and age-specifi c national mortality rates for heart

disease and stroke; and estimates of relative risk associ-

ated with SBP derived from meta-analyses.

The limitations of our study merit comment. The

sample of hypertensive blacks, although derived from

a nationally representative sample, was relatively small.

CIs surrounding estimates of blood pressure for spe-

cifi c groups were therefore relatively wide. Because

the number of deaths rises exponentially with age,

even small variation in estimates of racial disparity

in blood pressure among the elderly blacks can yield

appreciable changes in estimates. This phenomenon

is best illustrated by the results for women. Despite

a higher black-white disparity in SBP, our fi ndings

showed that elimination of this disparity would reduce

deaths more among black men than among black

women because the disparity for women is skewed

toward younger ages. It is for this reason that use

of a constant SBP yielded much higher estimates

for women than men. In addition, because of small

subgroup sizes, we used an upper age category of 75

years or older. Mean life expectancy at birth in 2004

was 69.5 years for black men and 75.3 years for black

women.1 Use of this cutoff underestimates the impact

of these disparities on deaths among elderly black

women. For these reasons, fi ndings that racial dispar-

ity in SBP disproportionately affects male mortality

should be viewed with caution pending more precise

estimates of racial disparity in blood pressure control

among men and women of advanced age.

These caveats notwithstanding, our fi ndings sug-

gest that racial disparity in hypertension control con-

tributes appreciably to deaths among blacks from heart

disease and stroke. Our analyses highlight the need

to more fully understand the causes of these dispari-

ties and develop viable strategies to eliminate them,

particularly clinician attention to adherence barriers

among patients.

To read or post commentaries in response to this article, see it online at http://www.annfammed.org/cgi/content/full/6/6/497.

Key words: Race/ethnicity; blacks; mortality; heart disease; stroke; hypertension; blood pressure; control

Submitted October 28, 2007; submitted, revised, January 29, 2008; accepted March 3, 2008.

Funding support: Funding was provided by the Robert Wood Johnson Foundation and by a grant from the National Heart, Lung, and Blood Institute (R01 HL081066-01A2).

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