Is HF Underrepresented in National Mortality Statistics?
Aims Mortality attributed to a disease is an important public health measure of the 'burden' of that disease. A discrepancy has been noted between the high mortality rates associated with heart failure (HF) and the share of deaths ascribed to HF in official mortality statistics. It was our main aim to estimate excess mortality associated with HF and use the estimates to better understand the burden of HF.
Methods and results Excess mortality was defined as the difference in mortality rates between individuals with and those without HF. An epidemiological model was formulated that allowed deriving age-specific excess mortality rates in HF patients from HF incidence and prevalence. Incidence and prevalence were estimated from yearly collected cross-sectional data from four nationally representative General Practice registries in the Netherlands. The year 2007 was chosen as a reference. Next, excess mortality rates were used to calculate numbers of deaths among HF patients and compare the figures with national cause-of-death statistics. The latter were found to be more than three times smaller than the former (roughly 6000 vs. 21 000). Further, by applying HF prevalence and mortality rates to a life table of the Dutch population, average numbers of life years lost due to HF were calculated to be 6.9 years.
Conclusion National mortality statistics strongly underestimate the number of deaths associated with HF. Moreover, the high mortality rate in HF patients amounts to a remarkably large number of life years lost given the advanced age of disease onset.
National mortality and cause-of-death statistics are important tools in monitoring public health and in planning health policy. Also in the case of heart failure (HF), cause-of-death data have been used by several researchers, amongst others to answer the question whether or not mortality rates have been improving. However, selecting an underlying cause of death only reveals the tip of the iceberg of the underlying pathology. Singling out one of, maybe, several potentially mortal processes present at the time of death, can result in distortions of perspective regarding their relative importance.
As is well-known to all devoted to the care of those with HF, these patients suffer from a severe disease with high mortality rates and poor prognosis. Moreover, the prevalence is high; it has been estimated that in the 51 countries represented in the European Society of Cardiology, with a total population of 900million, at any moment there are at least 15million patients with HF. In the USA there are some 5 million patients. Also the costs in terms of resources spent are considerable, being responsible for a share of about 2% of national expenditures on health care. Thus, in terms of public health, HF represents a heavy burden.
However, there is a discrepancy between the severity and high prevalence of HF and the 'share' of deaths attributed to HF in cause-of-death statistics. This raises the question of whether HF might be underreported in mortality statistics. For example, in a study of death certificates in Scotland over the years 1979 through 1992, Murdoch et al. found that HF 'is rarely officially coded as the underlying cause of death'. They concluded that 'death from HF is substantially underestimated by official statistics'.
The primary aim of this study was to estimate the 'excess' mortality in patients with HF, and to compare it with mortality figures attributed to HF in national vital statistics. A secondary aim was to use the estimated age-specific mortality rates in HF patients to derive a few other measures often used as yardsticks for assessing the burden of a disease, in particular numbers of life years lost. Excess mortality rates were derived by using readily available data on prevalence and incidence in combination with mathematical modelling of the epidemiological dynamics of HF.
Abstract and Introduction
Abstract
Aims Mortality attributed to a disease is an important public health measure of the 'burden' of that disease. A discrepancy has been noted between the high mortality rates associated with heart failure (HF) and the share of deaths ascribed to HF in official mortality statistics. It was our main aim to estimate excess mortality associated with HF and use the estimates to better understand the burden of HF.
Methods and results Excess mortality was defined as the difference in mortality rates between individuals with and those without HF. An epidemiological model was formulated that allowed deriving age-specific excess mortality rates in HF patients from HF incidence and prevalence. Incidence and prevalence were estimated from yearly collected cross-sectional data from four nationally representative General Practice registries in the Netherlands. The year 2007 was chosen as a reference. Next, excess mortality rates were used to calculate numbers of deaths among HF patients and compare the figures with national cause-of-death statistics. The latter were found to be more than three times smaller than the former (roughly 6000 vs. 21 000). Further, by applying HF prevalence and mortality rates to a life table of the Dutch population, average numbers of life years lost due to HF were calculated to be 6.9 years.
Conclusion National mortality statistics strongly underestimate the number of deaths associated with HF. Moreover, the high mortality rate in HF patients amounts to a remarkably large number of life years lost given the advanced age of disease onset.
Introduction
National mortality and cause-of-death statistics are important tools in monitoring public health and in planning health policy. Also in the case of heart failure (HF), cause-of-death data have been used by several researchers, amongst others to answer the question whether or not mortality rates have been improving. However, selecting an underlying cause of death only reveals the tip of the iceberg of the underlying pathology. Singling out one of, maybe, several potentially mortal processes present at the time of death, can result in distortions of perspective regarding their relative importance.
As is well-known to all devoted to the care of those with HF, these patients suffer from a severe disease with high mortality rates and poor prognosis. Moreover, the prevalence is high; it has been estimated that in the 51 countries represented in the European Society of Cardiology, with a total population of 900million, at any moment there are at least 15million patients with HF. In the USA there are some 5 million patients. Also the costs in terms of resources spent are considerable, being responsible for a share of about 2% of national expenditures on health care. Thus, in terms of public health, HF represents a heavy burden.
However, there is a discrepancy between the severity and high prevalence of HF and the 'share' of deaths attributed to HF in cause-of-death statistics. This raises the question of whether HF might be underreported in mortality statistics. For example, in a study of death certificates in Scotland over the years 1979 through 1992, Murdoch et al. found that HF 'is rarely officially coded as the underlying cause of death'. They concluded that 'death from HF is substantially underestimated by official statistics'.
The primary aim of this study was to estimate the 'excess' mortality in patients with HF, and to compare it with mortality figures attributed to HF in national vital statistics. A secondary aim was to use the estimated age-specific mortality rates in HF patients to derive a few other measures often used as yardsticks for assessing the burden of a disease, in particular numbers of life years lost. Excess mortality rates were derived by using readily available data on prevalence and incidence in combination with mathematical modelling of the epidemiological dynamics of HF.
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