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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
Circ Cardiovasc Qual Outcomes. Author manuscript; available in PMC 2013 May 1.
Published in final edited form as:
PMCID: PMC3407684
NIHMSID: NIHMS375504

NATIONAL SURVEILLANCE DEFINITIONS FOR HYPERTENSION PREVALENCE AND CONTROL AMONG ADULTS

Matthew Tyler Crim, MD, MSc, MA,1 Sung Sug (Sarah) Yoon, RN, PhD,2 Eduardo Ortiz, MD, MPH,3 Hilary K. Wall, MPH,1 Susan Schober, PhD,2 Cathleen Gillespie, MS,1 Paul Sorlie, PhD,3 Nora Keenan, PhD,1 Darwin Labarthe, MD, MPH, PhD,1 and Yuling Hong, MD, MSc, PhD1

Abstract

Background

Clear and consistent definitions of hypertension and hypertension control are crucial to guide diagnosis, treatment, and surveillance. A variety of surveillance definitions are in frequent use, resulting in variation of reported hypertension prevalence and control, even when based on the same data set.

Methods and Results

To assess the variety of published surveillance definitions and rates, we performed a literature search for studies and reports that utilized NHANES data from at least as recent as the 2003-2004 survey cycle. We identified 19 studies that used various criteria for defining hypertension and hypertension control, as well as different parameters for age-adjustment and inclusion of subpopulations. This resulted in variation of reported age-standardized hypertension prevalence from 28.9% to 32.1% and hypertension control from 35.1% to 64%. We then assessed the effects of varying the definitions of hypertension and hypertension control, parameters for age-adjustment, and inclusion of subpopulations, on NHANES data both from 2007-2008 (n=5,645) and 2005-2008 (n=10,365). We propose standard surveillance definitions and age-adjustment parameters for hypertension and hypertension control. Utilizing our recommended approach with NHANES 2007-2008 data, the age-standardized prevalence of hypertension in the US was 29.8% (standard error 0.62%) and the rate of hypertension control was 45.8% (standard error 4.03%).

Conclusions

Surveillance definitions of hypertension and hypertension control vary in the literature. We present standard definitions of hypertension prevalence and control among adults and standard parameters for age-adjustment and population composition that will enable meaningful population comparisons and monitoring of trends.

Keywords: hypertension, epidemiology, surveillance, health policy, prevention

Hypertension (HTN) is a prevalent condition worldwide and a major risk factor for cardiovascular disease (CVD).1 Mortality from stroke and ischemic heart disease doubles with each 20 mmHg increase in systolic blood pressure (SBP) from levels as low as 115 mmHg, and with each 10 mmHg increase in diastolic blood pressure (DBP) from levels as low as 75 mmHg.2 In 2010, the estimated cost of HTN was $76.6 billion in the United States (US) alone.1 Improvement in the awareness, treatment and control of HTN is essential to reduce associated morbidity and mortality.

Healthy People (HP) is a decennial national plan for disease prevention and health promotion coordinated primarily by the US Department of Health and Human Services and developed with input from federal, state, and local governments, professional societies, businesses, and other groups.3 Utilizing baseline surveillance data, HP 2010 established objectives related to blood pressure (BP) including a reduced proportion of adults with HTN and increased proportion of adults whose HTN is controlled. HP 2020 was launched in late 2010.4

Clear definitions of HTN and HTN control are crucial to guide diagnosis, treatment, and surveillance to monitor progress towards HP objectives. HTN is defined clinically as SBP 140 mmHg or greater or DBP 90 mmHg or greater averaged over two or more readings on two or more visits following an initial screening.5 In cross-sectional surveys, BP measurements are generally limited to a single point in time, and alternate definitions of HTN are thus applied in surveillance studies. Investigators have employed a variety of surveillance definitions resulting in variation of reported HTN prevalence and control, even when based on the same data set.1,6-23

Surveillance cannot rely solely on self-reported history of HTN that can be obtained from interview surveys, but must also include measurement of BP to account for undiagnosed HTN and status regarding control. Surveillance definitions of HTN typically apply the same BP cutoffs as the clinical definition (SBP ≥ 140 mmHg or DBP ≥ 90 mmHg) to measurements obtained in a single visit. Individuals currently taking antihypertensive medication are also usually classified as having HTN. In order to capture individuals with a history of HTN, investigators variably include self-report of ever being told of having HTN or being told on two or more occasions of having HTN, reflecting the measurement on two subsequent visits in the clinical definition. Exclusion of pregnant women also varies across studies, as well as the age range over which prevalence is calculated.

HTN control is defined clinically as SBP < 140 mmHg and DBP < 90 mmHg as a result of treatment by lifestyle modification or pharmacologic therapy.5 Some guidelines recommend the treatment goals for individuals with diabetes mellitus (DM) and chronic kidney disease (CKD) as SBP < 130 mmHg and DBP < 80 mmHg.5, 24, 25 The proportion of individuals with controlled HTN may be calculated relative to all individuals with HTN, or only those being treated. Adjustment for the lower HTN control threshold among individuals with DM or CKD also varies in the literature. HTN control can be captured in cross-sectional surveys that include BP measurement data and can identify individuals with a history of HTN or currently on antihypertensive medications, whose BP level is below the HTN threshold. Individuals with a history of HTN that are not currently on medication may have achieved HTN control through lifestyle modification or other nonpharmacologic methods.26 They may also simply exhibit variation in BP levels between occasions of measurement.

Differences in data analysis and BP measurement methodology further contribute to variability in published data. Age-adjustment of crude rates to a standard population allows comparison of proportions over time despite changing age distributions. Because HTN prevalence increases with age, the age groupings and standard population used for adjustment alter the calculated rate.27 The number of BP measurements averaged for each individual also varies in published data.

This paper recommends a standard surveillance definition for HTN prevalence and control reached by consensus between the Centers for Disease Control and Prevention (CDC) and the National Heart, Lung, and Blood Institute of the National Institutes of Health (NIH). This definition will enable tracking of HP 2010 and HP 2020 objectives and facilitate consistent comparisons. We first review the literature to examine the variation in reported HTN prevalence and control proportions in published analyses of NHANES data. We then present HTN prevalence and control data from NHANES 2007-2008 and 2005-2008, and we examine the changes in these results caused by varying several aspects of the definitions and data analysis parameters discussed above.

Methods

Literature Review

We performed a literature search for studies and reports that assessed HTN prevalence and control utilizing NHANES data from the 2003-2004 cycle and more recent survey cycles with inclusion of data no further back than 1999. We searched MEDLINE for scholarly articles using the terms HTN, BP, NHANES, prevalence, control, trends, and epidemiology together and in several combinations. We also identified published results from government reports and bibliography searches. Relevant data and analysis methods were abstracted and tabulated by HW, CG, and MC. Each abstraction was reviewed for accuracy by at least two authors and disagreements were reconciled by consensus.

NHANES

HTN prevalence and control were measured using data from the National Health and Nutrition Examination Surveys (NHANES). Survey design and protocol for BP measurement are described in the supplemental methods. The 2005-2008 surveys from which the data presented in this paper are derived were approved by the NCHS Ethics Review Board, and all participants provided written informed consent. See online supplemental methods section for details about the NHANES survey.

Data Analysis

Adults were defined as having HTN if they meet any of the following criteria: (1) SBP 140 mmHg or greater, (2) DBP 90 mmHg or greater, or (3) current use of antihypertensive medication. HTN prevalence was calculated with all individuals aged 18 years and older in the denominator, excluding pregnant women. HTN control was defined as SBP less than 140 mmHg and DBP less than 90 mmHg in an individual that has been prescribed antihypertensive medication and is currently taking that medication. The HTN control proportion was calculated with all individuals with HTN in the denominator (18 years and older excluding pregnant women).

Crude and age-adjusted HTN prevalence estimates are presented with percent and standard errors of percent – an absolute standard error of the estimate and not a relative assessment of the standard error. Data are presented from both one survey cycle (two years, 2007-2008) and two survey cycles (four years, 2005-2008) as each survey cycle provides information regarding trends and enlarging the survey population allows for a greater degree of age-adjustment and subpopulation analysis. Estimates of HTN prevalence were age-adjusted to the 2000 US standard population using either three age groups (18-39, 40-59, 60 years and older) or four age groups (18-39, 40-59, 60-74, 75+) for 2007-2008 data. Based on 2005-2008 data, estimates were age-adjusted using four age groups (18-39, 40-59, 60-74, 75+), five age groups (18-34, 35-44, 45-54, 55-64, 65+) and seven age groups (18-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80+), consistent with HP2020.28

Age-adjusted rates for HTN control were calculated using the 2000 US standard population and the subpopulation of individuals who had HTN in three age groups (18-39, 40-59, 60 years and older) and four age groups (18-39, 40-59, 60-74, 75+) for 2 years of data (2007-2008). HTN control was age-adjusted to four age groups (18-39, 40-59, 60-74, 75+) and five age groups (18-34, 35-44, 45-54, 55-64, 65+ and 18-49, 50-59, 60-69, 70-79, 80+) with four years of data (2005-2008). Age-adjustment weights for the subpopulation of individuals with HTN were calculated from the NHANES 2007-08 survey cycle (Table 1). Weights calculated from NHANES cycles since 2001 yielded similar results, and we thus used the most recent data. Sample weights accounting for the differential selection probabilities and adjusted for non-response and non-coverage were incorporated to produce unbiased estimates. Statistical analyses were conducted using the SAS System for Windows (release 9.1; SAS Institute Inc, Cary NC) and SUDAAN (release 9.0; Research Triangle Institute, Research Triangle Park, NC).

Table 1
Age-adjustment weights for hypertension control based on subpopulation of individuals with hypertension: NHANES 2007-08 (n=2,113)

Results

Literature Review

We identified 984 studies for review in the literature search, and 19 met criteria for inclusion (Supplemental Figure 1). Among the 72 studies we conducted abstract review for at the last stage of literature review, 53 were excluded for the following reasons: 19 reported data from NHANES survey that did not include data from the 2003-2004 or more recent cycles, 19 did not include data on hypertension prevalence or control, 8 did not report data from NHANES surveys, and 7 included data only from limited subpopulations. The study characteristics are presented in Supplemental Table 1, and the results are presented in Supplemental Table 2.1, 6-22 Three studies reported only HTN prevalence, six studies reported only HTN control, and 10 studies reported both HTN prevalence and control. All studies defined HTN by SBP ≥ 140 mmHg or DBP ≥ 90mmHg, and all but one also used current medication to define HTN. Four studies classified individuals as having HTN if they were ever-told that they had HBP, three studies if they were twice-told, and 12 studies did not use any criterion related to having been told that they had HTN. Of the 16 studies that reported HTN control, seven used only treated hypertensive individuals in the denominator, seven used all hypertensive individuals in the denominator, and two studies reported results using each denominator separately.

The age ranges of individuals included in the studies varied: six of the studies included age ≥18 years; two included 18-74 years; seven included ≥20 years; one 25-84 years; one ≥30 years; one ≥60 years; and one ≥65 years. Two studies focused on HTN in individuals with comorbid DM or CKD. Four studies excluded pregnant women, 13 studies included pregnant women, and pregnancy exclusion was not relevant to the two studies focused on the elderly. One study focused on Mexican or Mexican American race/ethnicity. Among studies focused on the general population, six adjusted for the lower HTN control threshold in individuals with DM or CKD, and eight did not.

Nine studies reported only crude rates, six studies reported only age-adjusted rates, and four studies reported both crude and age-adjusted rates. Studies that reported age-adjusted rates used the same standard population and age groupings for age-adjustment of both HTN prevalence and control. Age groupings varied across studies; each investigator employed distinct age groupings with the exception of four studies that used the three groupings (18 or 20-39, 40-59, and 60+ years). The 2000 US standard population was most commonly used for age-adjustment, but individual investigators also used 2000 US Census populations. No study used age-adjustment weights based on the subpopulation of individuals with HTN, though one author did mention this approach in the discussion section.14 Nine studies averaged all available BP measurements for each individual, three studies excluded the first BP measurement and averaged the remaining two or three BP measurements, and seven studies did not specify or were unclear regarding BP averaging.

The different definitions, populations, and data analysis parameters described above resulted in variation in reported HTN prevalence and control proportions even with all studies relying on NHANES data. Among studies focused on the adult population, crude HTN prevalence varied from 28.9% to 49.9%,16, 22 and age-adjusted HTN prevalence varied from 28.9% to 32.1%.6, 22 Studies focused on subpopulations reported HTN prevalence from 14% (Mexican and Mexican-American men) to 70.8% (adults 65 years and older).15, 18 Studies that classified individuals as having HTN if they had been told of high BP (HBP) on one or two occasions reported higher prevalence proportions than studies that used only measured BP and current medications. Among studies focused on the adult population, crude HTN control varied from 37% to 52.9%,12, 21 and age-adjusted HTN control varied from 35.1% to 64%.6, 10 Studies focused on subpopulations reported HTN control from 29.6% (adults 30 years and older with HTN and DM) to 63.9% (adults with HTN on medication).9, 13

NHANES

A total of 6,228 individuals aged 18 years and older were sampled in 2007-08, of whom 233 were not interviewed or examined, 295 were missing BP measurements (SBP and DBP), and 55 were pregnant women. Excluding these, there were 5,645 individuals available for analysis. In the 2005-06 survey, there were 5,563 individuals aged 18 years and older, of whom 229 were not interviewed or examined, 277 were missing BP measurements, and 337 were pregnant women (pregnant women were purposefully oversampled in this cycle) yielding 4,720 individuals for analysis. There were thus 10,365 individuals for the two cycles combined, 2005-2008.

The crude HTN prevalence among US adults based on NHANES 2007-2008 was 30.7% (Table 2). Age-adjustment with three age-groups (18-39, 40-59, 60 years and older) to the 2000 US standard population results in a HTN prevalence of 29.6%. Age-adjustment with four age-groups (18-39, 40-59, 60-74, 75 years and older) to the 2000 US standard population yields a HTN prevalence of 29.8% (Table 2). Age-adjustment with the same four age-groups including individuals who have ever been told of HBP increased the HTN prevalence to 35.2% (Table 2). Including only those individuals who have been told on two or more occasions of HBP attenuated this increase in HTN prevalence to 32.9% (Table 2). The additional individuals included with these criteria had a SBP < 140 mmHg or DBP < 90 mmHg and were not on antihypertensive medication.

Table 2
Crude and age-adjusted hypertension prevalence:NHANES 2007-2008 (n=5,645)

Physician-obtained BP measurements may be elevated relative to nurse or ambulatory measurements, but this effect may be attenuated with repeat BP measurement.29 We examined the effect of excluding the first BP measurement from analysis and averaging the second and third BP measurements. Adjusting to four age groups as above, HTN prevalence decreased to 29.4% excluding the first BP measurement (Table 2). Pregnant women are excluded from the calculation of HTN prevalence above. In NHANES 2007-08, there were 55 total pregnant women. Inclusion of this group in the general population resulted in a HTN prevalence of 29.7% (Table 2).

The crude proportion of HTN control among US adults based on NHANES 2007-2008 was 48.4% (Table 3). Age-adjustment with three age-groups as above to the subpopulation of individuals with HTN results in HTN control of 48.4% (Table 3). Age-adjustment with four age-groups as above to the subpopulation of individuals with HTN also yields a HTN control of 48.4% with a standard error of 1.49% (Table 3). Age-adjustment with the same four age-groups to the 2000 US standard population results in HTN control of 45.8% and increases the standard error to 4.03% (Table 3). Returning to age-adjustment with four age-groups to the subpopulation of individuals with HTN, including individuals who have ever been told of HBP increased HTN control to 55.4% (Table 3). Including only those individuals who have been told on two or more occasions of HBP attenuated this increase in HTN control to 50.4% (Table 3). These additional individuals are not on antihypertensive medication and have BP < 140/90 mmHg. Excluding the first BP measurement increased HTN control to 50.0% (Table 3). Inclusion of pregnant women resulted in HTN control of 48.4% (Table 3).

Table 3
Crude and Age-Adjusted hypertension control among hypertensives: NHANES 2007-2008 (n=2,113)

The crude HTN prevalence among US adults based on NHANES 2005-2008 was 30.4% (Table 4). Age-adjustment with four groups as above to the 2000 US standard population results in a HTN prevalence of 29.5% (Table 4). Age-adjustment with seven age groups (18-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80 years and older) to the 2000 US standard population, the parameters used in HP 2020, yields a HTN prevalence of 29.2% (Table 4). The crude proportion of HTN control among US adults based on NHANES 2005-2008 was 46.0% (Table 5). Age-adjustment with five age-groups (18-49, 50-59, 60-69, 70-79, 80 years and older) to the subpopulation of individuals with HTN results in HTN control of 45.9% with a standard error of 1.06% (Table 5). Age-adjustment with the same five age-groups to the 2000 US standard population results in HTN control of 43.8% with an increased standard error of 1.48% (Table 5).

Table 4
Crude and age-adjusted hypertension prevalence: NHANES 2005-2008 (n=10,365)
Table 5
Crude and age-adjusted hypertension control among hypertensives: NHANES 2005-2008 (n=5,744)

Discussion

A uniform surveillance definition of HTN prevalence and control is required for monitoring and evaluation, for HP objectives and other purposes. A review of the literature demonstrated variation in the definitions, populations, data analysis parameters, and results based on NHANES data. We thus propose a standard approach to HTN prevalence and control among adults uniquely suited to monitor population trends over time based on NHANES data. We recommend that the definitions of HTN prevalence and control used in the HP 2010 Operational Definition be employed as the standard surveillance definitions (Table 6).30, 31

Table 6
Recommended definitions and age-standardization parameters

In data analysis, we recommend that results of up to three BP measurements obtained by AHA-recommended protocol should be averaged.32 Crude rates for HTN prevalence and control should be reported to allow assessment of current burden along with age-adjusted rates to enable comparisons over time and between population subgroups with different age distributions. HTN prevalence and control should be age-adjusted to the 2000 US standard population using four age groups (18-39, 40-59, 60-74, 75 years and older) with two years of data from a single survey cycle. Age-adjustment of aggregated data from multiple survey cycles may utilize a larger number of age-groupings, such as seven for HTN prevalence (18-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80 years and older) and five for HTN control (18-49, 50-59, 60-69, 70-79, 80 years and older) used in HP 2020 (Table 6).33

Application of the recommended definition to NHANES 2007-2008 data revealed HTN prevalence and control of 29.8% and 45.8%, respectively. HP 2010 established the objective of a reduced HTN prevalence to 14% from a baseline prevalence of 26% based on data from NHANES 1988-94.34 The current HTN prevalence reflects an increase from the baseline and trend in the opposite direction of the objective; however, HTN prevalence has been stable at approximately 30% since 1999.7 The HP 2010 objective for HTN control was an increase to 68% from a baseline of 25% based on data from NHANES 1988-94. The current HTN control rate reflects an encouraging trend, though it remains short of the objective. The HP 2010 objectives were set with age-adjustment using the same seven age-groups (18-29, 30-39, 40-49, 50-59, 60-69, 79-79, 80 years and older) for HTN prevalence and five age-groups (18-49, 50-59, 60-69, 70-79, 80 years and older) for HTN control as above to the 2000 US standard population.

Monitoring HTN prevalence and control in the general population raises several considerations. While clinical definitions of HTN rely on BP measurements repeated on several visits to establish a diagnosis, cross-sectional surveys capture BP at a single visit. The recommended surveillance definitions for HTN prevalence and control are formulated with the methodological and logistical constraints of cross-sectional studies in mind. Surveillance measures are distinct from clinical measures and serve the purpose of following population trends, rather than an individual patient, over time. Individuals classified as having HTN by the clinical and surveillance definitions would be expected to differ.

The surveillance definitions also include individuals who are currently taking medications as treatment for HTN. These individuals are presumed to have been prescribed medication as a result of satisfying the clinical definition of HTN. Individuals with HTN who are not currently taking antihypertensive medication may thus represent new cases or have some barrier to taking medication (failure to prescribe, lack of understanding, unable to obtain, refusal, etc.). The recommended surveillance definition for HTN control uses current antihypertensive medication use as a marker of HTN in an individual with a BP below the HTN threshold (< 140/90 mmHg).

There are a number of nonpharmacologic therapies for HTN, and lifestyle modification is featured in the current Joint National Committee report (JNC 7).5, 26 The recommended surveillance definition does not include individuals who have met the clinical definition of HTN and achieved BP control by nonpharmacologic means, and may therefore underestimate HTN prevalence and control. The population with HTN controlled by nonpharmacologic means may be captured by expanding the HTN definition to include individuals who have ever been told of HBP, or, more consistent with the clinical definition, who have been told on two or more occasions that they have HBP. Past analysis of NHANES III (1988-1991) data reveals sufficient validity of self-reported HTN relative to JNC 7 guidelines in non-Hispanic whites and non-Hispanic black women with a medical visit in the past year, but similar validation has not been repeated with subsequent iterations of NHANES.35 Self-report of chronic conditions including HTN has also been validated in other population surveys.36

Specific subgroups also pose unique challenges to HTN prevalence and control surveillance. Though HTN in pregnancy is an important problem that can affect maternal and fetal health, the recommended definition excludes pregnant women due to differences in the underlying etiology and natural history of HTN in this subpopulation.37 Some guidelines for HTN control in individuals with comorbid DM or CKD recommend a lower BP threshold (< 130/80 mmHg).5, 24, 25 However, the evidence base for these recommendations is controversial with recent randomized controlled trials (RCTs) demonstrating that achieving lower BP thresholds may not reduce cardiovascular mortality or morbidity.38, 39 An additional RCT is underway to assess the impact of lower HTN control thresholds in a broader population.40

The recommended surveillance definition does not address DM or CKD populations directly, as the ability to reliably detect these comorbidities varies across cross-sectional surveys including NHANES. Indeed, using different formulae for calculating the estimated glomerular filtration rate (eGFR) – either the Modification of Diet in Renal Disease (MDRD) formula or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula – in order to classify CKD status in epidemiological studies yields different results.41 Recent analyses of HTN control below the lower BP threshold of 130/80 mmHg in individuals with DM and CKD based on NHANES data indicate that adjusting for these groups would result in decreased HTN control in the general population (Supplemental Tables 1 and 2).11, 13

Differences in data analysis may also contribute to apparent differences in measures of HTN prevalence and control. HTN varies with age, and crude prevalence rates thus reflect the age distribution of the survey sample.27 To enable meaningful comparisons and assess temporal trends, rates are adjusted to a standard population, but different age groupings and standard populations yield different adjusted rates. HTN control may be age-adjusted to a standard population representative of the overall population or representative of the subpopulation of individuals with HTN. Using a standard representative of the overall population will inflate the younger age groupings relative to the subpopulation of individuals with HTN.

Adjustment to the 2000 US standard population resulted in a decreased estimate of HTN control in our data relative to adjustment to the subpopulation of individuals with HTN, 45.8% vs 48.4%, respectively (Table 3). This is consistent with lower levels of HTN control in younger age groups.6, 42 We presented weights for the hypertensive subpopulation in NHANES 2007-2008 (Table 1) that should, where appropriate, be used as a standard for adjustment in future investigations focused on HTN control alone. Use of these weights resulted in a decreased standard error. Analyses that compare HTN control to control of other diseases or health measures will need to use a common standard population and age groups in order to permit meaningful comparisons of multiple health indicators.

While each NHANES two-year cycle provides information about recent trends, aggregating data from multiple survey cycles increases the number of study subjects and enables more reliable assessment of subpopulations and age-adjustment using more subgroups. The current NHANES BP measurement protocol and standardization effectively minimizes variability from observer and technical error.43 The use of automated blood pressure measurement devices is increasingly common, and in the NHANES 2007-08 and 2009-10 surveys one such device was tested in parallel with the protocol described above to assess the accuracy and consistency of measurements by the device for potential use in future surveys.44

BP measurements obtained by physicians have been demonstrated to be elevated relative to measurements obtained by nurses.45 NHANES relies on repeated BP measurement by physicians specifically trained to use proper technique. Excluding the first BP measurement and averaging the subsequent measurements in an attempt to adjust for this “white coat effect” resulted in a small decrease in HTN prevalence, but a relatively larger increase in HTN control. This suggests that individuals being treated with antihypertensive medication may experience a greater elevation of the initial BP reading than those not being treated. Egan and colleagues performed a similar analysis with a sample of NHANES 2007-08 data and found a significant decrease in both systolic and diastolic BP values between the first and second BP readings (-2.6/-0.8 mmHg) and the first BP reading and the average of the next two BP readings (-3.6/-1.1 mmHg).7 The degree to which exclusion of the first BP measurement controls for the white coat effect is unclear as the BP of the study subjects in other settings (e.g. ambulatory or home) is unknown and all measurements are obtained by a physician in a single visit.

While this analysis focused on NHANES data, surveillance data related to BP may be derived from several national surveys, each with unique strengths and limitations. The National Ambulatory Medical Care Survey (NAMCS) is an annual sampling of physician office visits with BP measurement and physician coding.46 NAMCS data cannot be used to calculate general population prevalence, but HTN control can be determined among ambulatory care patient visits. Uncontrolled HTN in NAMCS is identified in the setting of a physician visit, and this reflects an important area for quality improvement. The Behavioral Risk Factor Surveillance System (BRFSS) and National Health Interview Survey (NHIS) include state-level self-reported data from the general population but do not include BP measurement.47, 48 Additional state-level data could be obtained by expanding the NHANES sample or conducting state-specific HANES, such as the State Cardiovascular Health Examination Survey.49

The recommended definitions for HTN prevalence and control and their application to NHANES data have several limitations that suggest areas for improvement. The reliance on medication use in the recommended definitions may exclude nonpharmacologic control of HTN. Lifestyle change is an important component of HTN control, and validation of HTN self-report may permit future analyses to include individuals who have been told on two or more occasions of HBP by a health care provider. This paper does not address HTN awareness or treatment; however, these are important measures that also vary in the published literature by the definitions employed and merit future consideration.

This paper recommends a standard surveillance definition of HTN prevalence and control for assessment of temporal trends and progress toward HP objectives based on national cross-sectional survey data. Application of this definition to NHANES 2007-2008 data demonstrates that HTN prevalence has increased relative to the HP 2010 baseline and is tracking in the opposite direction of the objective, although it has remained stable over the past decade. HTN control has increased from the HP 2010 baseline, though it remains short of the objective. Improvements in HTN prevalence and control consistent with HP objectives are important to reduce the burden of associated diseases.

What is Known?

  • Hypertension is highly prevalent in the U.S. and around the World and its control is suboptimal
  • A variety of surveillance definitions for hypertension and hypertension are in frequent use

What this Article Added?

  • We found a wide variation of prevalence of hypertension and hypertension control when different definitions, inclusion/exclusion criteria and age adjustment schemes were used by examining 19 published studies using NHANES 2003-4 or more recent cycles
  • We proposed standard surveillance definitions of hypertension prevalence and control among adults and standard parameters for age-adjustment and population composition to enable meaningful population comparisons and monitoring of trends
  • We reported the age-standardized prevalence of hypertension and hypertension control rate for NHANES 2007-8 using the recommended definitions

Supplementary Material

supplement

Acknowledgments

The recommended surveillance definitions for HTN prevalence and control are the result of collaboration among the CDC’s Division for Heart Disease and Stroke Prevention (DHDSP) and National Center for Health Statistics (NCHS), and the NIH’s National Heart, Lung, and Blood Institute (NHLBI). All authors participated in conference calls and corresponded by e-mail regarding the recommended definitions. Multiple manuscript drafts were circulated to all offices for review and comment. Special thanks to Nancy Sonnenfeld (NCHS), who assisted in early discussions of the manuscript.

Footnotes

DISCLOSURES

None.

Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

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