The Incidence and Prevalence of Congestive Heart Failure in Rochester, Minnesota

DECEMBER 1993

VOLUME 68

The Incidence and Prevalence of Congestive Heart Failure in Rochester, Minnesota RICHARD J. RODEHEFFER, M.D., STEVEN J. JACOBSEN, M.D., PH.D., BERNARD J. GERSH, M.B.,CH.B., D.PmL.,* THOMAS E. KOTTKE, M.D., M.S.P.H., HUGH A. MCCANN, M.D., KENT R. BAILEY, PH.D., AND DAVID J. BALLARD, M.D., PH.D. Although congestive heart failure is a fairly common clinical syndrome and the societal costs associated with its care are high, relatively little is known about the incidence or prevalence of the condition in the community. Using the resources of the Rochester Epidemiology Project, we identified all 46 persons through 74 years of age who had a new diagnosis of congestive heart failure during 1981 and all 113 persons with a prevalent diagnosis on Jan. 1, 1982, in the city of Rochester, Minnesota. After confirming the diagnosis in the medical record by using criteria similar to those in the Framingham study, we found the annual incidence of congestive heart failure to be 110 per 100,000 after adjusting for age. Incidence rates were higher among male than among female study subjects (157 versus 71 per 100,000). In both male and female subjects, the incidence generally increased with advancing age, reaching 1,618 per 100,000 and 981 per 100,000, respectively. Prevalence rates on Jan. 1, 1982, demonstrated similar patterns. Overall, the prevalence of congestive heart failure was higher among male than among female subjects (327 versus 214 per 100,000) and increased exponentially with advancing age, reaching almost 3% in both sexes. Survival after a diagnosis of congestive heart failure was extremely poor, with only 80% alive at 3 months and 66% at 1 year. These data underscore the effect of congestive heart failure in the community and provide estimates of the number of persons who might benefit from early intervention.

°

From the Division of Cardiovascular Diseases and Internal Medicine (RJ.R., BJ.G., T.E.K.), Section of Clinical Epidemiology (S.J.J., T.E.K.), and Section of Biostatistics (K.R.B.), Mayo Clinic Rochester, Rochester, Minnesota; Division of Cardiology (H.A.M.), University of California, San Diego, California; and Thomas Jefferson Health Policy Institute (DJ.B.), Charlottesville, Virginia. *Current address: DC.

Georgetown University Medical Center, Washington,

This study was supported in part by Research Grants AR 30582 and HL 24326 from the National Institutes of Health, Public Health Service, and by a clinical epidemiology student research training grant from Merck, Sharp & Dohme. Dr. Ballard is supported in part by a Career Development Award from the Merck, Sharp & Dohme/Society for Epidemiologic Research Clinical Epidemiology Fellowship Program. Address reprint requests to Dr. R. J. Rodeheffer, Division of Cardiovascular Diseases, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905.

Mayo Clin Proc 1993; 68:1143-1150

Congestive heart failure is a common clinical syndrome that often represents the end stage of any of several cardiac disease entities. In the United States, more than 2,000,000 persons are thought to be affected by congestive heart failure.l-' and the incidence of congestive heart failure is thought to exceed 400,000 cases per year.' The National Hospital Discharge Survey listed congestive heart failure as the primary diagnosis on 643,000 hospital dismissal records in 1989. These dismissals accounted for more than 5,000,000 person-days of hospitalization' and represent a near-doubling in hospitalization rates for congestive heart failure since 1973.4 These numbers may be expected to increase in the future because of the aging of the US population,' which may be compounded by an increasing incidence of conges-

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© 1993 Mayo Foundation for Medical Education and Research

1144 INCIDENCE AND PREVALENCE OF CONGESTIVE HEART FAILURE

tive heart failure." Morbidity and mortality after the onset of congestive heart failure are extremely high. Of the patients diagnosed with congestive heart failure, half succumb to their disease within 2 years and up to 60 to 70% within 3 years.v' New data, however, suggest that interventions are available that can decrease this high mortality somewhat.t" Despite the burden this syndrome places on society and the potential for intervention, population-based data about the incidence and prevalence of this condition are relatively scarce. A Swedish study of men born in 1913 found the incidence of congestive heart failure to increase with advancing age, from 150 per 100,000 among those 50 to 54 years of age to more than 1,000 per 100,000 among men 61 to 67 years 0Id,13,14 These rates were somewhat higher than the estimates obtained by the Framingham study, which found the incidence of congestive heart failure to increase from 200 per 100,000 among 45- to 54-year-old men to 800 per 100,000 among men 65 to 74 years of age.15.16 In the Framingham cohort, incidence rates for men were higher than those for women until after age 84 years. Comparisons between these two studies are limited, however, because of differences in the definition of cases of congestive heart failure, age groupings, and population samples: Furthermore, how well these samples generalize to the US population is unknown. Because of the public health importance of this clinical syndrome and the limitations in the existing epidemiologic literature, this study was undertaken to document the incidence and prevalence of congestive heart failure in the population of Rochester, Minnesota. By retrospective application of the criteria used in the Framingham heart study to the Rochester population, estimates of the incidence of congestive heart failure during the calendar year 1981 and the prevalence of congestive heart failure on Jan. 1, 1982, were calculated. In addition, with the availability of follow-up data, population-based survival estimates were derived. METHODS Case Ascertainment.-Population-based epidemiologic research is possible in Rochester, Minnesota, because health care in the community is delivered by a small number of providers. Most care is provided through the Mayo Clinic, which has maintained a unified medical record system with its two affiliated hospitals for the past 80 years. The dossiertype medical record contains readily accessible information about both inpatient and outpatient visits.'? Diagnoses and surgical procedures in a record are listed on a face sheet, which, in turn, is coded and indexed. A diagnostic index is maintained that includes all diagnoses made during outpatient office visits, clinic consultations, emergency department visits, nursing home care, hospital admission, autopsy

Mayo Clin Proc, December 1993, Vol 68

examination, and death certification. In addition, the medical records of other health-care providers within the area are indexed and can be retrieved through the Rochester Epidemiology Project. Medical records are available from the Olmsted Medical Group, Olmsted Community Hospital, Rochester State Hospital, University of Minnesota Hospitals in Minneapolis, and Department of Veterans Affairs Hospital in Minneapolis. Data from several small community hospitals in surrounding counties, from several local family practitioners in Rochester, and from local nursing homes are also indexed and added to the central data bank at the Mayo Clinic. Consequently, detailed information about the medical care provided to all residents of the community is available for study. This system ensures nearly complete case ascertainment for almost all major illnesses diagnosed among residents of the city of Rochester. The potential value of these data for population-based epidemiologic studies has been described previously.P:" Using the data available through the diagnostic index, we identified all records of persons 0 through 74 years of age who had been newly diagnosed with congestive heart failure during the period ofJan. 1, 1981, through Dec. 31,1981 (that is, the incidence cohort), This process identified all persons with an initial diagnosis of congestive heart failure regardless of the setting in which a diagnosis was made-inpatient, outpatient, or other. In addition, we identified all persons 0 through 74 years-of age who had a diagnosis of congestive heart failure on or before Jan. 1, 1982 (that is, the prevalence cohort). To ensure complete case ascertainment, we retrieved and reviewed all medical records of persons categorized under the diagnostic rubric for congestive heart failure from the hospital adaptation of the International Classification of Diseases, eighth revision (code 427)-a total of 366 potential cases of congestive heart failure. The diagnosis of congestive heart failure was confirmed through a thorough review of the medical record. Physicians' notes were examined for mention of several major and minor criteria for congestive heart failure. 15 The major diagnostic criteria were as follows: paroxysmal nocturnal dyspnea, orthopnea, abnormal jugular venous distention, pulmonary rales, cardiomegaly, pulmonary edema, presence of a third heart sound, and central venous pressure of more than 16 em of water. The minor criteria included edema, night cough, dyspnea on exertion, hepatomegaly, pleural effusion, tachycardia (more than 120 beats/min) and weight loss of 4.5 kg or more in 5 days (this finding was considered a major criterion if it occurred during therapeutic interventions for congestive heart failure). Persons were assigned a diagnosis of congestive heart failure if two major criteria were present or, alternatively, one major and two minor criteria were present concurrently. Furthermore, all medical records were reviewed by one of us (RJ.R.) to ensure that diagnostic

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INCIDENCE AND PREVALENCE OF CONGESTIVE HEART FAILURE

criteria could not be attributable to conditions other than congestive heart failure. In addition to fulfilling diagnostic criteria, persons must have established residence in Rochester, Minnesota, at least I year before diagnosis for inclusion in the incidence study. This guideline was intended to exclude persons who might have moved into the city for the diagnosis or treatment of their congestive heart failure. For the prevalence study, persons were required to be living in the city on Jan. 1, 1982, and to have established residence at least I year before that date. Persons were excluded because of failure to meet diagnostic criteria (N = 111), residency requirements (N = 33), or age criteria (N = 58) or because of death before the study period (N = 27) or before the prevalence date (N = 13). After exclusions, 46 incident cases of congestive heart failure forthe period ofJan. 1, 1981, through Dec. 31,1981, and a total of 113 prevalent cases on Jan. I, 1982, remained for study. Follow-up for analysis of survival was obtained through the comprehensive medical records. At 7 years, 1 of the 46 members of the incidence cohort (2%) and 5 of the 113 members of the prevalence cohort (4%) had been lost to follow-up. Data Analysis.-The population of the city of Rochester, Minnesota, 0 through 74 years of age was considered at risk for development of congestive heart failure. Incidence rates were calculated as the observed number of cases divided by the age- and sex-specific person-years of observation. Estimates of the population at risk were derived from decennial census data for 1980 and 1990. 19 Rates were directly ageand sex-adjusted to the population structure of US whites in 1980. Prevalence rates were calculated by dividing the observed number of cases on Jan. 1, 1982, by the estimated city population on that date. Ninety-five percent confidence intervals were constructed about the point estimates of incidence and prevalence. by assuming a Poisson distribution. Survival function estimates were derived by using the method described by Kaplan and Meier.i" and differences were tested with use of the log-rank test." Expected survival was calculated on the basis of decennial life tables for whites in the West North Central census division."

1145

Table I.-Characteristics ofIncident Cases of Congestive Heart Failure, Rochester, Minnesota, Jan. 1, 1981, Through Dec. 31, 1981 Characteristic Total Sex Female Male NYHAclass* I II III

IV

Unknown Etiologic factor Ischemicheart disease Other Unknown Age (yr)

Subjects No. %

46

100

19

41 59

4 8

9 17 24 48 2

27

II

22 I

23 5 18

50 II

2 2

4 4 24 67

<1

1-54 55-64 65-74

II

31

39

*NYHA= New YorkHeart Association.

criteria, 33 (72%) had two or three, and 1 had only one major criterion and at least two of the minor criteria. The distribution of the diagnostic criteria for the incidence cases is shown in Figure 1. The presence of pulmonary rales was the most commonly found major criterion, 74% of the cases having this trait. Among the minor criteria, the presence of dyspnea on exertion was the most common, 76% of the incidence cohort reporting this symptom. The incidence rate (and 95% confidence limits) for congestive heart failure after adjustment for age and sex was 110.4 per 100,000 (78.1,142.7). Overall, male subjects had a higher age-adjusted incidence rate of congestive heart failure at 157.3 per 100,000 (97.3, 217.3) in comparison with female subjects at 70.7 per 100,000 (38.6, 102.8). Analysis of the incidence rates by age (Table 2) showed a general ageassociated increase. After infancy (younger than 1 year old), rates tended to increase exponentially with advancing age. RESULTS Incidence.-During 1981,46 new cases of congestive heart Among male subjects, rates increased from 76 per 100,000 failure were diagnosed in the city of Rochester, Minnesota, among those 45 to 49 years old to more than 1,600 per in 27 male and 19 female subjects (Table 1). Among the 100,000 among those 65 to 69 years old and thereafter incidence cohort, 33 (72%) were in New York Heart Asso- declined to 938 per 100,000 in the 70- to 74-year-old ageciation functional class III or IV. In 23 of the cohort (50%), group. Among female subjects, however, the age-associated ischemic heart disease was determined to be the cause of increase was less dramatic and possibly delayed; rates inheart failure; the cause was indeterminate in 18 (39%). Of creased from 81 per 100,000 among those 55 to 59 years old the other five cases, valvular heart disease was the etiologic to 981 per 100,000 among those 70 to 74 years old. factor in four and cardiomyopathy in one. Overall, 12 of the Prevalence.-On Jan. 1, 1982, 113 persons (57 male and 46 cases (26%) had four or more of the major diagnostic 56 female subjects) living in the city of Rochester had a

1146 INCIDENCE AND PREVALENCE OF CONGESTIVE HEARTFAILURE

Mayo Clin Proc, December 1993, Vol 68

Major

80

60 40 20 ~ 0

0> > ;:l '0 0

a.

0

Crne

JVD

PND

PEd

Ral

5-3

Ven

Minor

80

•

~ Incidence cohort

60 40

Prevalence cohort

20

0

DOE

Ede

Hrne

NCo

PEt

Tae

WtL

Fig. 1. Percentage of major and minor diagnostic criteria present for incident and prevalent cases of congestive heart failure in Rochester, Minnesota. Major criteria: Cme == cardiomegaly; JVD == jugular venous distention; PND == paroxysmal nocturnal dyspnea or orthopnea (two pillows or more); PEd == pulmonary edema; Ral == rales; S-3 == third heart sound; Yen == venous pressure of more than 16 cm of water. Minor criteria: DOE == dyspnea on exertion; Ede == peripheral edema; Hme == hepatomegaly; NCo == night cough; PE!== pleural effusion; Tac == tachycardia; WtL == weight loss of 4.5 kg or more in 5 days.

diagnosis of congestive heart failure. Among the 105 of these subjects who were first diagnosed with congestive heart failure in Rochester, the distribution of diagnostic criteria was strikingly similar to that of the incident cases (Fig. Table 2.-Incidence of Congestive Heart Failure, Rochester, Minnesota, Jan. 1, 1981, Through Dec. 31, 1981 Female subjects Age (yr) <1 1-44 45-49 50-54 55-59 60-64 65-69 70-74 0-74t 0-74t

No. 1

o o o

1 2 5 10 19

Rate*

Male subjects No.

Rate*

210.1 I 0 0 0 1 0 1 81.2 3 180.5 5 475.3 11 981.4 5 70.7 (16.4) 27 110.4 (16.5)

191.6

o

75.6 85.7 276.8 550.7 1,617.6 938.1 157.3 (30.6)

*Rate per 100,000 person-years. [Rates per 100,000 person-years, adjusted to age distribution ofDS whites, 1980 (standard error). [Rate per 100,000 person-years, adjusted to age and sex distribution of US whites, 1980 (standard error).

1). (The enumeration of diagnostic criteria may have been incomplete among eight persons whose condition was diagnosed elsewhere. These persons were eliminated from the tallies of criteria met.) Of the 105, 28 (27%) had four or more major diagnostic criteria, 66 (63%) had two or three major criteria, and 11 (10%) had one major and at least two minor criteria (Fig. 1). Cardiomegaly was the most common major criterion among the prevalence cohort, 82 (78%) having this finding noted in the medical record. Dyspnea on exertion was the most common minor criterion, 78 (74%) having this symptom. Overall, the age- and sex-adjusted prevalence rate (and 95% confidence limits) for congestive heart failure was 265.8 per 100,000 (216.3, 315.2) for the city of Rochester. The prevalence rate was higher among male subjects at 327.3 per 100,000 (241.5, 413.1) than among female subjects at 213.6 per 100,000 (157.2,270.1). The age-associated increase in prevalence rates among male subjects was similar to that in the incidence cohort (Table 3). Rates declined from 86.1 per 100,000 among boys 0 to 4 years of age to 0 for male subjects 10 to 44 years old. Thereafter, rates increased from 74.4 per 100,000 among men 45 to 49 years old to 2,595.5 per 100,000 among those 65 to 69 years

INCIDENCE AND PREVALENCE OF CONGESTIVE HEART FAILURE

Mayo Clin Proc, December 1993, Vol 68

Table 3.-Prevalence of Congestive Heart Failure, Rochester, Minnesota, Jan. 1, 1981, Through Dec. 31, 1981 Age (yr) 0-4 5-9 10-44 45-49 50-54 55-59 60-64 65-69 70-74 0-74t 0-74t

Female subjects No. Rate* 0 0 0 1 3 4 8 12 28 56

Male subjects No. Rate* 86.1 48.7 0 74.4 84.5 730.9 1,203.5 2,595.5 2,765.0 327.3 (43.8)

0 2 1 0 0 0 72.6 1 225.6 1 323.8 8 716.8 11 1,134.8 18 2,743.8 15 213.6 (28.8) 57 265.8 (25.2)

*Rate per 100,000 person-years. tRates per 100,000 person-years, adjusted to age distribution of US whites, 1980 (standard error). tRate per 100,000 person-years, adjusted to age and sex distribution of US whites, 1980 (standard error).

old and 2,765 per 100,000 among those 70 to 74 years old. Among women, rates increased exponentially from 72.6 per 100,000 for those 45 to 49 years of age to 2,743.8 per 100,000 for those 70 to 74 years old. Survival.- The survival among persons in the incidence cohort was particularly poor (Fig. 2). Only 80% remained alive 3 months after diagnosis, and 66% were alive at 1 year. After 8 years, the cumulative survival was only approximately 30%, less than half that expected for the general population. Survival among female subjects was similar to that among male subjects but tended to be poorer among persons in New York Heart Association functional class IV than among those in functional classes I, II, or

cf-

7ii 2:

::::l

DISCUSSION In this study, we report on the incidence and prevalence of congestive heart failure in a well-defined populat~on. These data indicate that congestive heart failure develops in 0.2 to 1% of the population 55 to 74 years of age within a specific year. Furthermore, at a given point in time, approximately 1 to 3% of the population has the diagnosis of congestive heart failure. These data also demonstrate the pronounced effect of initial diagnosis on survival, with an initial hazard being 5 times greater in the incidence than in the prevalence cohort. In a comparison of incidence rates from the current study with those from the Framingham study (Tables 2 and 4), estimates from this study are lower than those from the Framingham study for both male and female subjects younger than 65 years of age. Among those 65 to 74 years old, however, rates for men are almost double those from the Framingham study, and for women, they are nearly half

100

80

80

cf-

7ii

60

.O!:

.O!:

en

III. The numbers were too small, however, for meaningful comparisons. The mortality among the prevalence cohort was less than that among the incidence cohort (Fig. 3). At 3 months, the cumulative survival was 96%; at 1 year, 80% of the prevalence cohort remained alive. At 8 years after the prevalence date, the cumulative survival among the prevalence cohort was 32%. Although formal tests of the differences in survival between the incidence and prevalence cohorts would not be straightforward because 33 of the incident cases (72%) were also in the prevalence cohort (that is, they survived from their 1981 date of diagnosis until Jan. 1, 1982), the mortality was substantially more during the first year among incident cases than among prevalent cases.

100

60

1147

2:

40

::::l

en

20

0

20

Male

0

2

3

4

5

6

7

40

8

Yearsfollowing diagnosis

Fig. 2. Survival after diagnosis of congestive heart failure in incidence cohort, Rochester, Minnesota, 1981, stratified by sex.

0

0

2

3

4

5

6

7

8

Yearssince January 1, 1982

Fig. 3. Survival among persons with congestive heart failure in total prevalence cohort, Rochester, Minnesota, Jan. 1, 1982, stratified by sex.

1148

INCIDENCE AND PREVALENCE OF CONGESTIVE HEART FAILURE

Table 4.-Incidence* of Congestive Heart Failure: Comparison of Framingham, Massachusetts, and Swedish Cohorts With Population of Rochester, Minnesota Age (yr)

Framinghamt Men Women

Rochester Men Women

45-54 55-64 65-74

200 400 800

80 402 1,319

SO-54 55-60 61-67

100 300 500

0 128 724

Swedish men born in 1913*

Rochester (men)

ISO 430 1,020

86 402 1,618

*Rates per 100,000 person-years. [Data based on 34 years of follow-up experience." *Data based on 17 years of follow-up experience."

again those from the Framingham study. Unfortunately, the age- and sex-specific number of persons in whom congestive heart failure developed is not available in the published material from the Framingham study; thus, formal statistical analysis is precluded. Because of the sample size and confidence limits of the estimates, the differences between the current study and the Framingham study may be more apparent than real. If these differences do not represent random variation, however, several other potential explanations can be proposed. First, the discrepancies may be due to the differences in study design. In the Framingham study, persons were asked to return every second year for detailed clinical assessments. In the course of these examinations, signs and symptoms of congestive heart failure may have been elicited that would not have otherwise come to clinical attention. In contrast in the current study, data were collected from review of data in the medical record noted during the course of routine medical care. As such, only persons who sought medical care could have been enrolled in this study. Most likely, this limitation would result in an underestimate of the actual incidence and prevalence of congestive heart failure. The lower incidence rate among persons younger than 65 years of age is consistent with this hypothesis. By applying the same logic, however, the actual incidence rates among the Rochester population of persons 65 years old or older would be even higher than those reported herein. Alternatively, perhaps the diagnosis is only delayed for persons in Rochester in comparison with the Framingham cohort. This "Will Rogers phenomenon" (artifactual shift)" would cause incidence rates to be relatively lower among the younger age-groups and relatively higher among the older age-groups. Evidence for this possibility is found in the New York Heart Association functional class at the time of initial diagnosis: 2 of 11 persons (18%) between

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the ages of 55 and 64 years were in class I, whereas only 2 of 31 persons (6%) 65 to 74 years of age were in class I. This explanation, however, seems unlikely to be solely responsible for the differences. A second reason for these differences could be the method of data collection. In our study, we had to rely on notation by physicians of the signs and symptoms that served as our markers for congestive heart failure. In the Framingham study, however, the data were collected as part of a structured examination. Again, this difference would tend to produce a downward bias of the estimates in the current study. The relatively higher-incidenee of congestive heart failure among both men and women 65 years of age or older could not be explained through this mechanism. A third reason for the differing findings between this study and the Framingham study could be the intrinsic differences between the study samples. Although the Framingham study was, in fact, a true cohort study, it was nonetheless a cohort of volunteers with a 31 % nonresponse rate." The Rochester experience, in contrast, represents a true population-based study. The observed differences may be due to the potential for bias imposed by the volunteers who constituted 14% of the Framingham cohort. Furthermore, elimination of the prevalent cases of coronary artery disease may have caused the Framingham cohort to have fewer cases of congestive heart failure than would be expected in the general population. Although this rationale could explain, in part, the lower rates among the older agegroups in the Framingham study, the apparent lack of this difference in the younger age-groups needs explanation. This finding could reflect the different causes of congestive heart failure in young persons in comparison with older persons. Finally, the differences may also reflect underlying variations in the populations. The higher incidence of congestive heart failure among elderly Rochester residents could be due to a net immigration of persons at greater risk for development of congestive heart failure in comparison with the general population. This explanation seems unlikely, however, because only two subjects in the incidence cohort were not residents of Rochester 10 years before their diagnosis. Residents of Rochester, Minnesota, may differ from those in Framingham, Massachusetts, relative to risk for the development of congestive heart failure. Were this the case, differences in risk factors for the development of congestive heart failure in these two communities should be sought. Alternatively, these differences may result from secular changes in incidence in the population. Despite these differences in incidence rates, the survival after diagnosis of congestive heart failure was strikingly similar between this study and the Framingham data. This result might suggest that the patients from the Rochester cohort had no more severe dis-

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INCIDENCE AND PREVALENCE OF CONGESTIVE HEART FAILURE

ease than did those from the Framingham study. If true, this fact would argue against an underascertainment bias in this study. Unfortunately, data on functional status are not available from the Framingham study. Comparisons between this study and the Swedish cohort of men born in 191314 present similar problems (Table 3). Age-specific rates among Rochester men are lower than those reported for the Swedish men in the younger agegroups. This consistency would make any of the aforementioned biases due to underascertainment in the current study more probable. In addition, the Swedish study used an examination specific for eliciting signs and symptoms related to congestive heart failure. With this approach, systematic differences between active searching for signs and symptoms and retrospective review of medical records could be amplified. Alternatively, these differences could reflect actual variations between the Swedish and Rochester study populations in the risk for development of congestive heart failure. In addition to the Framingham and Swedish studies, recently published data from the National Health and Nutrition Examination Survey (NHANES) are of value for comparison." This study reported congestive heart failure prevalence (but not incidence) estimates for all noninstitutionalized men and women in the United States. Symptom information from the cross-sectional study was explicitly obtained by questionnaire, and physical signs were determined by systematic physical examination. These uniformly obtained data were combined into a clinical screening system for heart failure. The prevalence estimates from the NHANES were generally higher than those from the current study, perhaps because the systematic ascertainment of signs and symptoms in the NHANES makes detection of mild cases of congestive heart failure more likely in comparison with abstraction of signs and symptoms from medical records. Consequently, the NHANES prevalence data may provide an estimate of our underascertainment of incidence cases of congestive heart failure. Despite the advantages afforded by our population-based study, several limitations must be considered when the results are interpreted. First, as previously mentioned, these rates were based on persons who sought clinical attention for their congestive heart failure. Undoubtedly, other cases resolved before medical assistance was sought, had not progressed sufficiently to be detected, or resulted in death without detection. These factors would tend to underestimate the incidence and prevalence of congestive heart failure. Second, this study was limited to the data reported in the records of medical-care providers for residents of this community. If specific signs and symptoms were systematically omitted from the notes of physicians because they were considered synonymous with congestive heart failure, some patients

1149

may not have been included in the study sample because 0 failure to fulfill diagnostic criteria. For 111 patients a diagnosis of congestive heart failure was recorded by physician, but the record lacked sufficient supporting data to establish that diagnosis. The inclusion of these cases would dramatically increase the incidence rates; hence, rates among the elderly might be even higher. The retrospective application of our strict diagnostic criteria may also have resulted in an underidentification of mild cases of congestive heart failure (New York Heart Association class I or II) and, consequently, the identification of an apparently high proportion of severe cases (class IV). This study was also limited by the small size of the Rochester population. In 1981, fewer than 8,000 Rochester residents were older than 55 years of age and were at risk for development of congestive heart failure. This limitation is reflected in the wide confidence intervals about the point estimates of incidence and prevalence. Finally, this study may also be limited in its generalizability. The population of Rochester is predominantly white; no blacks or Asians were identified among the cases of congestive heart failure. In addition, the socioeconomic profile of the city of Rochester is primarily middle to upper-middle class, and few persons of extremely low socioeconomic class reside in the city. Nonetheless, because of the volunteer nature of the Framingham study, 23 these data provide the first estimates of congestive heart failure incidence for a total community population in the United States. Despite. these possible limitations, our findings underscore the high prevalence of congestive heart failure. Indeed, because our study did not include persons older than 74 years of age, it undoubtedly underestimates the total clinical and societal burden of congestive heart failure. The stringent diagnostic criteria used for this study certainly have underestimated the prevalence of heart failure in the community. Furthermore, analysis of hospitalization data suggests that improved survival among persons who suffer from coronary artery disease has led to an increase in incidence and prevalence of congestive heart failure in the population." Our community-based observations, coupled with the aging of the population, suggest that the burden this clinical syndrome imposes on society may be greater than previously recognized and will, in the future, increase more than was previously expected. These findings emphasize the importance of improved methods of detecting congestive heart failure and of decreasing the morbidity and mortality associated with this condition.

ACKNOWLEDGMENT We gratefully acknowledge Sondra L. Buehler for assistance in the preparation of the submitted manuscript, Sara L. Helgeson for data analysis, and Rita R. Black for data abstraction.

1150 INCIDENCE AND PREVALENCE OF CONGESTIVE HEART FAILURE

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Smith WM. Epidemiology of congestive heart failure. Am J Cardiol 1985; 55:3A-8A 2. Gibson TC, White KL, Klainer LM. The prevalence of congestive heart failure in two rural communities. J Chronic Dis 1966; 19:141-152 3. Graves EJ. 1989 summary: National Hospital Discharge Survey. Adv Data Vital Health Stat 1991; 199:1-11 4. Ghali JK, Cooper R, Ford E. Trends in hospitalization rates for heart failure in the United States, 1973-1986: evidence for increasing population prevalence. Arch Intern Moo 1990; 150:769-773 5. Rice DP, Feldman n. Living longer in the United States: demographic changes and health needs of the elderly. Milbank Q 1983; 61:362-396 6. Massie BM, Conway M. Survival of patients with congestive heart failure: past, present, and future prospects. Circulation 1987; 75(Supp14):IVll-IVI9 7. Wilson JR, Schwartz JS, Sutton MS, Ferraro N, Horowitz LN, Reichek N, et al. Prognosis in severe heart failure: relation to hemodynamic measurements and ventricular ectopic activity. J Am Coli Cardiol 1983; 2:403-410 8. CONSENSUS Trial Study Group. Effects of enalapril on mortality in severe congestive heart failure: results of the Cooperative North Scandinavian Enalapril Survival Study (CONSENSUS). N Engl J Med 1987; 316:1429-1435 9. Cohn IN, Johnson G, Ziesche S, Cobb F, Francis G, Tristani F, et al. A comparison of enalapril with hydralazine-isosorbide dinitrate in the treatment of chronic congestive heart failure. N Engl J Med 1991; 325:303-310 10. The SOLVD Investigators. Effect of enalapril on survival in patients with reduced left ventricular ejection fractions and congestive heart failure. N Engl J Med 1991; 325:293-302 11. Pfeffer MA, Braunwald E, Moye LA, Basta L, Brown EJ Jr, Cuddy TE, et al. Effect of captopril on mortality and morbidity in patients with left ventricular dysfunction after myocardial infarction: results of the Survival and Ventricular Enlargement trial. N Engl J Med 1992; 327:669-677 12. The SOLVD Investigators. Effect of enalapril on mortality and the development of heart failure in asymptomatic patients with reduced left ventricular ejection fractions. N Engl J Med 1992; 327:685-691

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