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Editorial
We are in the midst of a proclaimed epidemic of heart failure, as evidenced by increases in the number of hospitalizations for heart failure, the number of deaths attributed to heart failure, and the costs associated with care.1 In this issue of the Journal, we are provided with good news regarding the heart failure epidemic. Levy et al.2 report data from the Framingham Heart Study indicating that the survival of patients in the community who have a diagnosis of heart failure is (finally) improving and that the incidence of heart failure may be declining. As we consider the implications of these data, the complexity of the epidemic and our incomplete understanding of its genesis deserve comment. Is the Incidence of Heart Failure Changing? Surprisingly, few studies have described changes in the incidence of heart failure over time. Indeed, such studies are difficult. Standardized diagnostic criteria for heart failure must be applied consistently over time. Information on inpatient and outpatient cases, rather than events (hospitalizations), must be captured in a population-based setting. Ideally, these data would be sex- and race-specific. Fifty percent of persons with heart failure have preserved systolic function.3 Because the demographic characteristics, natural history, and response to therapy in persons with "diastolic heart failure" have not been fully defined, the relative incidence of the systolic and diastolic forms of heart failure over time should be ascertained. Finally, if we are to understand why the incidence of heart failure is changing, information about changes in the incidence and outcomes of conditions that cause heart failure should also be assessed. Frequently, studies report increases in the number of hospitalizations assigned a billing code for heart failure as evidence of the increasing incidence of heart failure. However, such data do not distinguish between cases and hospitalizations, rely on billing codes that have not been constant over time, are influenced by economic incentives and practice patterns, are usually not validated against standardized diagnostic criteria, and do not capture data on heart failure in outpatients. Although they provide important information about the economic burden of the diagnosis-related-group code for heart failure applied in our health care system, these studies do not provide a reliable estimate of the incidence of heart failure. However, investigators who used innovative data sets from an integrated health care system serving over 5 million persons with 30,000 cases of heart failure recently reported that the age- and sex-adjusted incidence of heart failure was stable from 1989 to 1999.4 That study included inpatients and outpatients with heart failure, and it identified cases, included persons of all ages and of ethnically diverse backgrounds, and made some attempts to validate diagnoses. Although reliance on billing codes remains an important limitation, this well-powered study suggested that in recent years, the incidence of heart failure has not changed. A small, population-based study that used standardized diagnostic criteria also found no change in incidence between 1981 and 1991.5 The current data from the Framingham Heart Study2 are ideally suited to assess changes in the epidemiologic features of heart failure. Although there may be some concern about sample size with respect to the detection of trends in incidence over time, they are the best data we have. The finding of any decrease in the incidence of heart failure in the midst of a "heart failure epidemic" is good news indeed. Using the period from 1950 to 1969 as a reference (rate ratio, 1.00), the authors found that the age-adjusted incidence of heart failure, in terms of the rate ratio, decreased to 0.87 in the 1970s, 0.87 in the 1980s, and 0.93 in the 1990s in men � a nonsignificant decline. In women, the age-adjusted incidence decreased to 0.63 in the 1970s, 0.60 in the 1980s, and 0.69 in the 1990s � a significant decline. Unfortunately, the analysis could not identify at what point in time the incidence of heart failure declined, and this is a crucial matter. A steady and incremental decline in incidence would have important implications for the current epidemic. However, the data strongly suggest that the decline in incidence occurred in the 1970s and that the incidence has subsequently remained stable. If this is the case, these findings are far less pertinent to the current epidemic than a more recent change would be. Why might the incidence of heart failure be decreasing? The prevalence of hypertension is decreasing, and control of hypertension (though suboptimal) has improved in recent decades.6,7 Because hypertension is an important risk factor for the development of heart failure, these data suggest a possible explanation for decreases in the incidence of heart failure. However, it could also be argued that more people now avoid death due to hypertension-related coronary and cerebrovascular events and thus remain at risk for heart failure � a phenomenon that would balance the reduction in hypertension-related heart failure. The effect that changes in the natural history of coronary disease may have on the incidence of heart failure is equally complex. Deaths from coronary disease have clearly declined, but studies differ as to whether this decline represents a decrease in the incidence of myocardial infarction or an improvement in therapy � factors with strikingly different implications for the incidence of heart failure.8,9,10 Indeed, a recent population-based study showed an increase in the incidence of myocardial infarction in women from 1979 to 1994,11 a finding that is difficult to reconcile with the decrease in the incidence of heart failure in women. Furthermore, obesity is a potent independent risk factor for heart failure.12 The striking recent increases in the prevalence of obesity make it difficult to understand how the incidence of heart failure can be declining, unless the decline was specific to the period from 1950 to 1970. A similar situation exists for diabetes, which is also a risk factor for heart failure. These issues demonstrate the complexity of the epidemic of heart failure and the difficulty in explaining it at a time when the epidemiology of diseases that lead to it is changing. Is Survival after Heart Failure Changing? In contrast to the complex issues related to the incidence of heart failure, changes in the rate of death due to heart failure may be relatively easy to understand. A previous Framingham Heart Study investigation in which survival after heart failure was analyzed for the period from 1948 to 198813 and a small, population-based study in which survival after heart failure was analyzed in 1981 and 19915 showed no improvement in survival after heart failure. These studies were performed before the widespread integration of angiotensin-converting�enzyme inhibitors into community-based practice. With data from the 1990s now incorporated, the Framingham Heart Study indicates that survival among patients with heart failure has improved. Again, the timing of the improvement cannot be determined from the statistical analysis, but examination of the data suggests that the improvement occurred primarily in the 1990s. These data are consistent with the results of a large study from Scotland that found decreases in mortality at one year among patients hospitalized for heart failure between 1986 and 1995.14 As emphasized by the authors of the current report, the reasons for the improvement in survival cannot be definitively ascertained. However, there is evidence that the use of angiotensin-converting�enzyme inhibitors and beta-blockers in patients with heart failure is increasing.15 This is the most appealing explanation and one that promises further improvements if the use of optimal therapy for heart failure in the community continues to increase. However, there are other possible explanations, including changes in the distribution of systolic and diastolic heart failure and changes in the causes of heart failure over time. Paradoxically, this much-needed good news for patients in whom heart failure is diagnosed will translate into further increases in the overall number of persons with heart failure in the community. Will the Epidemic of Heart Failure Continue? Projected population demographics clearly indicate a progressive increase in the segment of the U.S. population that is 65 years of age or older (Figure 1). Given the high incidence of heart failure in persons in this age category, only a dramatic decrease in incidence or a decrease in survival after heart failure, commensurate with the changes in population demographics, could prevent further increases in the number of persons with heart failure in this country. Survival after heart failure appears to be increasing, not decreasing, and the lack of convincing evidence that the incidence of heart failure has decreased since the 1970s in men or in women suggests that there is little hope for an imminent end to the heart failure epidemic. Indeed, these data underscore the complexity of the epidemic and our inability to understand with confidence whether � let alone why � the epidemiology of heart failure is changing.
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