Trends in Hypertension Prevalence, Treatment, and Control In a Well-Defined Older Population
To assess medical attention focused on hypertension (HBP) in the elderly, this study examines trends in HBP prevalence, treatment, and control status in a defined population of persons ≥65 years of age enrolled in a large HMO. Random samples of approximately 400 persons were drawn for the years 1967, 1974, 1981, and 1988. First recorded ambulatory pressures, available on over 90% of subjects in each period, were obtained from medical records. Prevalence of HBP (SBP ≥ 160 and/or DBP ≥95, and/or taking anti-HBP drugs) ranged between 44% to 53%. Proportion with HBP on treatment increased from 25% in 1967 to 60% in 1988 (P<.001); proportion on treatment and controlled (SBP<160, DBP<95) increased from 8% to 34% (P<.001). Mean population SBP declined from 155.2 in 1967 to 144.0 in 1988 (P<.001); mean DBP declined from 85.2 to 81.2 (P<.001). Proportion with isolated systolic hypertension (ISH) (SBP≥160, DBP<90) remained unchanged at 12% to 14%. Use of diuretics and adrenergic antagonist agents declined while use of beta blockers and newer classes of anti-HBP drugs increased significantly among treated hypertensives in the 1980s. These findings parallel HBP trends in younger adults from National Health Survey data though we find evidence of a substantial gap in addressing the problem in the elderly, who constitute the population at greatest risk of cardiovascular complications of HBP.
- HBP = hypertension
- anti-HBP = antihypertensive
- SBP = systolic blood pressure
- DBP = diastolic blood pressure
- ISH = isolated systolic hypertension
- ACE = angiotensin converting enzyme
- CAs = calcium antagonsts
HBP is the major modifiable risk factor for stroke and one of the major risk factors for coronary heart disease, congestive heart failure, and renal disease.1,2⇓ The rates of these costly HBP-related cardiovascular conditions are substantially higher in persons over age 65 than among those under 65.3,4⇓ Furthermore, elevated systolic blood pressure is associated with greater risk than elevated diastolic blood pressure in older persons.5,6⇓
The benefits of treating HBP were well established in randomized trials during the 1970s and early 1980s; however, because persons over age 65 were underrepresented in these studies, and because most studies focused on benefit of lowering diastolic blood pressure, there was a prevailing skepticism regarding the value and safety of lowering elevated blood pressure, in particular systolic pressure in older patients.7–9⇓⇓ This skepticism has been largely refuted by randomized trials during the 1980s, which document significant reduction in strokes and heart attacks among persons up to age 84 with HBP10–12⇓⇓ and specifically among older persons with ISH.13 Given this evolving state of knowledge, it is important to track and interpret secular trends in HBP control in the elderly as has been done so thoroughly for middle-aged adults.14–16⇓⇓ To address this need, the present study assesses changes in prevalence, treatment, and control status of HBP in a well-defined elderly population between the late 1960s and late 1980s.
Materials and Methods
The study was based at the Kaiser Permanente Center for Health Research (CHR), which has conducted a wide range of population-based studies in conjunction with the Kaiser Permanente Northwest (KPNW) Region health plan, a large group model HMO based in Portland, Oregon, with an enrollment of over 400,000 persons. Health plan members, who enroll through work site programs or open enrollment, are representative of the Portland metropolitan population in terms of age, sex, family income, and occupation and education of head of household. The members constituted 15% to 20% of that population between 1965 and 1990.17 During the period of our study the plan, drawing consistently on the same metropolitan market, showed steady annual growth, with 8% to 10% of members over age 65. Over 90% of members on reaching age 65 continue to receive their health care through the health plan, converting to Medicare as payer. The CHR has maintained access to comprehensive medical records for all KPNW members for research purposes since 1966.
Design and Data
For purposes of analyzing HBP trends, we conducted a retrospective medical record study, comparing prevalence estimates among samples of the health plan population ≥65 years of age at four points in time: 1967, 1974, 1981, and 1988. Simple random samples of 400 to 500 persons ≥65 years of age were drawn from the membership files of persons enrolled in the health plan at the beginning of each of the study years. Members who joined the plan as part of Medicare HMO demonstrations in the 1980s (TEFRA risk HMO and Social Health Maintenance Organization projects) were excluded from eligibility to avoid possible selection bias.
Trained medical record technicians reviewed each study subject’s medical record, beginning January 1 of the respective study years and abstracted data related to HBP and its current treatment according to explicit recording instructions. Blood pressures recorded during emergency room visits or acute hospital admissions were not eligible for inclusion. For each of up to five consecutive encounters at which blood pressure was recorded, the medical record technicians abstracted systolic and diastolic pressures and the names of any antihypertensive (anti-HBP) medications that were being prescribed for treatment of HBP. When more than one blood pressure was recorded at an encounter, the second reading was abstracted. To assure completeness of ascertainment of medications, technicians were provided with reference lists containing, in alphabetical order, the names of all generic and proprietary anti-HBP drugs in use during the respective study periods.
At least one medical encounter that included blood pressure readings occurred within 2 years of the beginning of each study period for 92%, 96%, 94%, and 97% of subjects sampled within the 4 respective periods. Table 1 shows distribution of the study populations by age group and gender. Trend analyses were based on the data abstracted from each subject’s first encounter in the study period that included a blood pressure recording. Systolic and diastolic blood pressures (SBP and DBP) and anti-HBP medication data were used to compute population mean blood pressures and HBP prevalence, treatment, and control status for the respective study periods. A subject was classified as having HBP if SBP was ≥160 mm mercury and/or DBP was ≥95 mm mercury and/or he/she was taking medication for treating HBP. A subject was classified as having ISH if SBP was ≥160 and diastolic pressure <90. HBP treatment and control status was classified as follows:
Untreated, uncontrolled = SBP≥160 and/or DBP≥95 and not receiving any anti-HBP medication.
Treated, uncontrolled = SBP≥160 and/or DBP≥95 and receiving one or more anti-HBP medications.
Treated, controlled = SBP<160 and DBP<95 and receiving one or more anti-HBP medications.
While the above definitions of HBP and ISH, which were widely recommended in practice through much of the time covered by this study, were used for our primary trend analyses, we also include summary trend data using more recently recommended definitions for HBP (SBP≥140 and/or DBP≥90) and ISH (SBP≥140, DBP<90).
For trend analysis, anti-HBP medications were assigned to one of the following classifications, based on pharmacologic mechanism for controlling HBP: diuretics, peripheral adrenergic antagonists, central alpha antagonists, beta blockers, angiotensin converting enzyme (ACE) inhibitors, calcium antagonists (CAs), other.18
We used logistic and ordinary linear regression to simultaneously control for the effects of age and gender while testing for the effect of study period on outcomes. For the dichotomous outcomes, which include prevalence of HBP, prevalence of ISH, proportion of subjects with DBPs or SBPs exceeding specified cutpoints, and proportion with controlled versus uncontrolled HBP, logistic regressions were used. For the continuous outcomes, mean SBP and mean DBP, linear regression analysis was used. The Mantel-Haenszel chi-square statistic was used to test for trends in class of anti-HBP medication used across study periods. Period trend tests for each age/sex group controlled for difference in age within groups. All analyses were performed using the SAS statistical software package (SAS Institute Inc). Unless otherwise stated, all P-values are 2-sided and the term significant implies a P<.05.
Overall prevalence of HBP among persons≥65 years of age showed a gradual but statistically significant decline, from 51% to 44% between 1967 and 1988 (Table 2). Analysis by subgroups shows HBP prevalence essentially unchanged over time for men while declining significantly among women. This decline in prevalence among women from Period 1 (1967) first became apparent in Period 3 (1981). Overall prevalence of ISH was unchanged over time; however, there was a significant decline in ISH among the subgroup of women 75+ years of age (Table 3).
Using SBP≥140 and/or DBP≥90 or receiving anti-HBP medications to define HBP and SBP≥140, DBP<90 to define ISH, prevalence rates were substantially higher than those in Table 2 and 3⇑, ranging 71%–77% and 34%–41%, respectively.
Means and Cutpoints
Population mean SBPs and DBPs both showed significant declines between 1967 and 1988; age and sex adjusted mean SBP declined from 155.2 mm Hg to 144.0 mm Hg and mean DBP declined from 85.2 mm Hg to 81.2 mm Hg (Tables 4 and 5⇓). The declining trends in mean SBP and DBP were significant for women 65 to 74 and 75+ years of age and for men 65 to 74 but were not observed among men 75+ years of age. Among women significant decline in mean SBP and DBP compared with Period 1 (1967) again was first observed in Period 3 (1981), while the significant declines among men 65 to 74 were first observed in Period 4 (1988). In all 4 study periods mean SBPs and DBPs were generally higher among women.
Improving trends in severity of blood pressure elevations between 1967 and 1988 were reflected in steady and significant declines in proportion with SBP of ≥180 mm Hg from 20% to 6% (P<.001), and in proportion with DBP ≥100 mm Hg from 16% to 6% (P<.001). These declining trends were observed consistently among subgroups of men and women 65 to 74 and 75+ years of age, though the decline in proportion with SBP ≥180 among males 75+ and with DBP ≥100 among females 75+ did not attain statistical significance at the P<.05 level.
Treatment and Control
Table 6 compares the distribution of persons with HBP by treatment and control status across the 4 study periods. Overall findings show decline in proportion untreated and uncontrolled (75% to 40%), increase in proportion on treatment but uncontrolled (17% to 26%) and, importantly, increase in proportion on treatment and controlled (8% to 34%). The trend toward increased percent on treatment and controlled, compared with those uncontrolled with or without treatment, was highly significant (P<.001) among all age-sex groups except males 75+ years of age, among whom borderline significant increase was observed (P=.141)
Analyzing the data using SBP ≥ 140 and/or DBP ≥90 to define uncontrolled HBP yields a much less favorable pattern over our period of observations, with decline in untreated and uncontrolled hypertensives from 83% to 63%, an increase in treated but uncontrolled from 14% to 30%, and a very modest attainment of only 7% on treatment and controlled as of 1988.
The distribution of class of anti-HBP medications prescribed for those with HBP who were on treatment changed over time (Table 7). Among the hypertensives who were on treatment in the 1967 sample virtually all were being managed with diuretic medications and 24% were receiving peripheral adrenergic antagonists (reserpine derivatives). By 1988, among hypertensives in the study sample who were on treatment, diuretic use had dropped to 73% and peripheral adrenergic antagonist use to 1%. Beta blockers, introduced in the mid-1970s, and ACE inhibitors and CAs, introduced in the 1980s, showed increasing frequency of use among treated hypertensives in the 1981 and 1988 survey subjects. Proportion of hypertensives being managed with one, two, or three drugs remained quite constant over the several study periods, with ranges of 70% to 78%, 20% to 24%, 2% to 6%, respectively.
This retrospective study of a defined population of persons 65 years of age and above between the late 1960s and late 1980s finds significant declines in prevalence of HBP and mean SBPs and DBPs and increases in percent with HBP who were receiving anti-HBP medication and in whom HBP was controlled. Virtually all of these favorable trends were first observed in the 1980s and were more pronounced among women than men. These findings among a defined older population are similar to trends in HBP control among representative samples of the US community dwelling adult population 18 to 74 years of age, based on data from National Health Examination Surveys (NHES) for the period 1960 to 1991;16 however, there is evidence of delay in time of appearance of favorable trends among the older population and substantial lack of HBP control in this age group.
In interpreting our findings and their implications for the larger population of older persons with HBP, strengths and potential limitations of our study should be recognized. While national health surveys conducted between 1960 to 1991 have tracked HBP status of the US adult population aged 18 to 74 at time intervals both before and following implementation of the National High Blood Pressure Education Program (NHBPEP) in 1972, these studies have provided only limited analysis of trends among persons over age 65 and contain no information on trends for persons over age 75.16 By contrast, the present study, spanning the same time period, focuses exclusively on trends among persons 65 years of age and above, and includes separate analyses for younger (65 to 74 years old) and older (75+ years old) subsets of male and female subjects. The setting from which our study samples were drawn is a well-established prepaid health plan, the membership of which is demographically reflective of the large metropolitan area in which it is located, hence providing an unselected sample of community dwelling older persons, except for the relatively small population of uninsured persons.17
For each of the 4 study periods, over 90% of persons in the respective samples were eligible for inclusion in our analyses by virtue of having at least one documented blood pressure in medical records. This level of eligibility compares favorably with response rates ranging between 70% to 87% among subjects selected for inclusion in the 4 nationwide HBP surveys conducted between 1960 and 199116 and response rates of 64% to 73%19 and 80% to 83%20 in two other community-based studies of HBP trends conducted in the 1970s and early 1980s.
The unit of analysis for our retrospective study was blood pressure recorded by a practicing physician or nurse on a single occasion, as documented in the subject’s medical record. Blood pressure data used for other trend analyses have been ascertained in a variety of ways, both within and across studies, including single and multiple measures using standardized methods in national surveys14,16⇓ and single recorded blood pressures abstracted in retrospective medical chart reviews similar to the present study.19 While such different approaches to documenting blood pressure clearly vary in degree of precision of measurement, nonetheless they describe quite similar population time trends respecting blood pressure levels and HBP treatment and control as discussed below. More importantly, “casual” blood pressures, recorded on a single occasion, while not recommended for diagnosis and monitoring of HBP in individual patients, have been found to be highly predictive of risk of future cardiovascular events in epidemiologic studies.22 In light of these considerations, the findings reported here may be considered both a valid and consequential profile of blood pressure trends in a representative population of older people.
Declining prevalence of HBP between the 1960s and late 1980s, as observed in the present study, has been observed among middle-aged and older adults in other trend studies covering all or part of this time interval.16,19–21⇓⇓⇓ Utilizing the 160/95 mm Hg definition of HBP, as in this study, NHES data between 1960 to 1962 and 1988 to 1991 documented a significant decline in prevalence of HBP among women 60 to 74 years of age (from 50% to 37%) but not among men 60 to 74 years of age (33% and 35%). In both data sets this decline became evident during the 1970s and persisted during the 1980s. In a medical record study of HBP trends in Rochester, Minnesota, for the periods 1960 to 1969 and 1970 to 1979, investigators also observed a significant decline in HBP prevalence for women, but not for men over age 65.19
Of interest, prevalence of ISH remained largely unchanged over time, with the exception of a decline among women 75 years of age and above. Trends in ISH prevalence are not reported in the NHES or Minnesota studies.
The observed decline in HBP prevalence in national health surveys is thought to be in part artifactual, attributable to methodological differences in measuring blood pressure among the surveys,16 and in part real, attributable to decline in prevalence of causal factors, in particular dietary salt intake.15 While the present study provides no direct evidence to explain the declining prevalence, the fact that the method for measurement of blood pressure remained essentially the same across all 4 study periods lends support to the conclusion that the decline is real. Why this decline appears to be limited to women remains to be explained.
Mean population SBPs and DBPs declined significantly among 60 to 74 year old men and women in the NHES analyses between 1960 to 1962 and 1988 to 1991. While these declines in mean blood pressure began to appear in survey data in the late 1970s, the major changes occurred between the early and late 1980s. Very similar timing of trends in mean blood pressures were observed among men and women age 65 to 74 as well as those 75 years of age or above in our study. Consistent with other studies of HBP in older persons, mean SBPs and DBPs were higher among women than men at all time intervals observed in the NHES studies and the present study.16
The lower population mean blood pressures as well as declining proportions of persons with relatively high SBPs (≥180 mm Hg) and DBPs (≥100 mm Hg) observed between the early and later 1980s are compatible with increased national emphasis on identification and treatment of HBP in older persons during this time period.4,23⇓
In assessing extent to which HBP was treated and controlled among older persons, we use as our criterion for control SBP of <160 mm Hg and DBP of <95 mm Hg among persons on treatment, which is the criterion generally in use in clinical practice and among other HBP trend studies conducted from the 1960s through the early 1980s.14–16,25⇓⇓⇓ (As with national trend data for persons 18 to 74 years of age, we find relatively low percentage of our population of persons ≥65 years of age with HBP who were on treatment (25%) and who were controlled (8%) in the 1960s with substantial increases in proportion on treatment to 60%, and more modest increases in proportion controlled to 34%, by the late 1980s (Table 6). By contrast, national surveys for approximately similar time periods showed a dramatic increase in proportion of hypertensives treated and controlled in the younger overall adult population from 29% in the 1976 to 1980 survey to 64% in the 1988 to 1991 survey.16
These differences in degree of HBP control among younger versus older persons are likely to be attributable to the fact that during the 1970s and 1980s major emphasis was focused on controlling elevated DBP, which is predominant among younger hypertensives, while relatively little emphasis was focused on controlling elevated SBP, which is predominant among older hypertensives.4,9,23⇓⇓ Given the strong evidence of benefits of controlling systolic HBP in older persons emerging from the Systolic Hypertension in the Elderly Program13 and other clinical trials reported in the early 1990s10,12⇓ and national attention to these important findings,11,24⇓ a substantial increase in proportion of older persons with controlled HBP may be anticipated when surveys are conducted in the 1990s.
Applying currently recommended definitions for uncontrolled HBP (SBP≥140 and/or DBP ≥90) and ISH (SBP≥140, DBP<90), the findings among our samples of older persons indicate particularly large gaps in HBP in need of greater medical attention.
Among the older hypertensives on treatment in the present study, proportional use of various classes of anti-HBP medication changed significantly over time. As reported in other trend studies of anti-HBP prescribed among both younger and older patients,26,27⇓ we observed a significant decline in diuretic use from virtually all treated hypertensives in 1967 to 73% in 1988. Beta blocker use emerged in the early 1980s and persisted at a relatively stable level of 25% to 31% of treated hypertensives throughout the decade, while the newly introduced ACE inhibitors and CAs were prescribed in 10% and 7% of treated cases by the late 1980s. The shift toward the latter newer, more costly anti-HBPs, despite their not having been tested in clinical trials of morbidity or mortality reduction among older hypertensives, and the corresponding decline in use of diuretics, which have been consistently proven to be effective in clinical trials involving older and younger hypertensives, has raised concerns.28,29⇓ It is noteworthy that decline in diuretic use to 73% in the older population in the present study is substantially less than declines in use to below 50%, with concurrent increases in ACE inhibitor and CA use to levels ranging between 15% to 30%, in other population based studies of anti-HBP use in the late 1980s and early 1990s.26,27⇓ Because of retrospective methods used in this and other studies it is not possible to discern the reasoning and appropriateness underlying the observed patterns of use of anti-HBP drugs.
The ultimate evidence of benefit from increased control of HBP in a population is corresponding decrease in mortality from HBP-related cardiovascular conditions. The dramatic decline in stroke and ischemic heart disease mortality in the United States in the 1970s and 1980s,30 including well-documented stroke mortality decline in the older population in which the present study was conducted,31 is to a substantial extent attributable to parallel increases in treatment and control of HBP.32 However, given the persisting high prevalence of uncontrolled HBP in the elderly at the beginning of the 1990s, as observed in this study, greatly increased efforts are called for to further prevent HBP-related morbidity and mortality in this high-risk and growing segment of the population.
This research was supported by National Institutes of Health grants RO1-AG05188 and RO1-AG12171. We thank Jill Mesa and staff, Teresa Kimes and Lee Randol Barker, MD for data collection, analysis, and manuscript review, respectively.
- Received September 16, 1997.
- Revision received October 15, 1997.
- Accepted October 24, 1997.
Vokonas PS, Kannel WB, Cupples LA. Epidemiology and risk of hypertension in the elderly. J Hypertens. 1988; 6 (suppl 1): S3 –S9.
Garland C, Barret-Connor E, Suarez L, Criqiu MH. Isolated systolic hypertension and mortality after age 60 years. Am J Epidemiol. 1983; 118 : 365 –376.
Frohlich ED. Hypertension in the elderly: Only the end of the beginning. Hypertension. 1994; 23 : 286 –287.
National High Blood Pressure Education Program Working Group. National High Blood Pressure Education Program on Hypertension in the Elderly. Hypertension. 1994; 23 : 275 –285.
SHEP Cooperative Research Group. Prevention of stroke by antihypertensive drug treatment in older persons with isolated systolic hypertension: final results of the Systolic Hypertension in the Elderly Program (SHEP). JAMA 1991; 250 : 2807 –13.
Dannenberg AL, Drizd T, Horan MJ, Haynes SG, Leaverton PE. Progress in the battle against hypertension changes in blood pressure levels in the United States from 1960 to 1980. Hypertension. 1987; 10 : 226 –233.
Burt VL, Cutler JA, Higgins M, Horran MJ, Labarthe D, Whelton P, Brown C, Rocella EJ. Trends in prevalence, awareness, treatment and control of hypertension in the adult US population. Data from the health examination surveys, 1960 to 1991. Hypertension. 1995; 26 : 60 –69.
Greenlick MR, Freeborn DK, Pope CR, eds. Health Care Research in an HMO. Baltimore, MD: John Hopkins University Press,. 1988; pp: 4 –16.
Sprafka JM, Burke GL, Folsom AR, Luepker RV, Blackburn H. Continued decline in cardiovascular risk factors: Results of the Minnesota heart survey 1980-1982 and 1985-1987. Am J Epidemiol. 1990; 132 : 489 –500.
Gordon T, Sorlie P, Kannel WB. Problems in the assessment of blood pressure: the Framingham study. Int J. Epidemiol. 1976; 5 : 327 –334.
Applegate WB, Rutan GH. Advances in management of hypertension in older persons. JAGS. 1992; 40 : 1164 –1174.
Monane M, Glynn RJ, Gurvitz JH, Bohn RL, Levin R, Avon J. Trends in medication choices for hypertension in the elderly. The decline of the thiazides. Hypertension. 1995; 25 : 1045 –1051.
Gifford RW, Kaplan NM. Thiazides and hypertension in the elderly. Hypertension. 1995; 25 : 1052 .
Morbidity, and Mortality Chartbook on Cardiovascular, Lung, and Blood Diseases. National Heart, Lung, and Blood Institute. Bethesda, Md. 1992; 23 –44.
Barker WH, Mullooly JP. Stroke in a defined elderly population, 1967-1985; a less lethal and disabling but no less common disease. Stroke. 1997: 28 : 284 –290.
MacMahon S, Cutler JA, Stamler J. Antihypertensive drug treatment. Potential, expected, and observed effects on stroke and coronary heart disease. Hypertension. 1989; 13 (Suppl I): 145 –150.