Background
Heart failure (HF) causes a significant burden for patients and healthcare systems in developed countries [
1,
2]. Approximately 50–75 % of patients with HF die within five years of diagnosis [
3,
4]. Evidence shows that HF accounts for 1–3 % of overall healthcare spending, mainly due to repeated hospital admissions and prolonged inpatient length of stay [
1]. In developed countries, prevalence of HF ranges from 1–3 %, rising to 10 % or more in those aged 75 years or older [
1,
2], while estimates in developing countries are not routinely reported.
The relationship between obesity, hypertension, smoking and cholesterol with cardiovascular morbidity is undisputed. Australia has made significant attempts to address risk factors contributing to the onset of chronic diseases [
5]. Public health policy on tobacco control, improvements in surgical treatment and the widespread use of lipid and blood pressure-lowering drugs have resulted in a significant decline in the burden of major cardiovascular diseases [
5‐
8]. Despite these improvements, the burden of diabetes and obesity in the population has steadily increased over time [
7].
Data on the incidence of HF is not reported in the Australian Institute of Health and Welfare (AIHW) periodic statistics [
9], while the Australian National Health Surveys (NHS) report prevalence rates based on self-report [
10]. However, self-reported data may underestimate the true burden of HF because the early stages of HF may be only mildly symptomatic; therefore many people may be unaware that they have the condition [
7]. Similarly, estimation based on mortality data may under-report the actual burden of HF, as the international classification of diseases (ICD) recommends coding underlying causes of death such as ischemic heart diseases rather than HF, which is often the terminal illness of other cardiovascular diseases [
10,
11]. Variation in the definition of HF and process of estimation therefore limit the validity and utility of data from these sources [
9,
10].
Despite the morbidity and economic burden to the community and poor patient outcomes, there is a deficiency in the systematic collection of data pertaining the incidence and prevalence of HF. Therefore, summarizing the data available from individual studies provides an opportunity to estimate the burden of HF. The present study systematically reviewed the literature to estimate the incidence and prevalence rates of heart failure in Australia.
Discussion
Our findings indicate that the prevalence of HF in the Australian population ranges from 1.0–2.0 %, and varies by Indigenous status, gender, age, and geographic location. The burden of HF was higher among Indigenous than non-Indigenous Australians, and in rural and remote than in capital city and metropolitan areas. In most of the studies reviewed, HF was more prevalent in women than in men.
As indicated in the AIHW reports, there are no studies reporting on the incidence of HF. [
7] The only data available was the number of new cases of HF diagnosed each year, estimated based on overseas data, which may not be generalizable to the population due to limitations inherent to the process of extrapolation [
24].
Our findings of the prevalence of HF in Australia (1.0–2.0 %) is congruent with data from Europe and North America where prevalence of HF range between 1.3 % and 2.2 % [
1,
27‐
29]. Consistent with existing knowledge [
30,
31] HF was three or more times higher in the elderly than in the population. In general, the NHS [
14‐
16] reported a lower prevalence of HF compared with the individual studies [
17,
18,
20,
26] which may be related to the use of self-reported diagnosis in the NHS [
7]. The significant proportion of previously undiagnosed HF patients [
19,
21] also reveal a chance of underestimation when HF is defined based on self-reported diagnosis.
In most of the studies [
14‐
16,
22] HF was twice more prevalent in women than men, although men were more affected than women in two other studies [
19,
21]. The inconsistency in the prevalence of HF by gender has been reported in several studies [
3,
32,
33]. In Australia, major risk factors of HF including coronary heart diseases, diabetes, and high blood pressure are higher in men than in women [
7,
34]. However, risk factors of HF such as diabetes, hypertension, and left ventricular dysfunction have stronger risk of progression to HF in women than men, which may explain the higher prevalence of HF among women [
30,
35]. The higher burden of HF among women could be also be attributed to the longer life expectancy and higher incidence of HF in later years of life in women than men [
36].
The higher prevalence of HF among Indigenous Australians is consistent with the existing literature. The latest Australian statistics shows that cardiovascular diseases are 1.3 times more common among Indigenous than their non-Indigenous counterparts [
8]. The excess burden of HF, cardiovascular diseases in general, in Indigenous population is related to the overall disparity in the social and economic status that impact on their health status [
22]. The risk factors of HF are also reported to be more prevalent among Indigenous population than the nationally reported data [
21].
According to previous studies [
22,
25] the disproportionately higher burden of HF in rural and remote towns is related to the concentration of older age inhabitants and higher prevalence of socio-demographic risk factors in these regions. Indigenous Australians, who have higher prevalence of HF also concentrate in rural and remote towns [
25]. The comparatively lower access to healthcare services in rural and remote regions, which may affect early identification and management of the risk factors predisposing to HF, could also contribute to the geographic disparity [
20,
23,
25].
The syndrome of HF has different causes and diverse clinical presentations, and long-term clinical evolution that makes its diagnosis challenging [
1,
37]. Studies based on self-reported diagnosis are likely to underestimate the burden of HF because participants may not know their HF status [
37,
38]. Limitations inherent to use of administrative data such misclassification may also compromise the validity of HF data from such studies. Therefore the overall estimate of the burden of HF is likely to be affected by the use of different definitions and measurement methods for HF.
This systematic review has some limitations. There were limited studies on epidemiology of HF in Australia and therefore studies that used varying HF definition (such as heart failure and oedema) were included in the review. Due to the limited number of studies, further description of the pattern of HF over time was not possible. Moreover, the search was restricted to PubMed indexed journals, and unpublished reports. As a result, articles published non-PubMed indexed journals may have been missed. Despite these limitations, the current review still provides valuable information on the prevalence of HF in the Australian population. Extensive and systematic literature search using pre-defined quality assessment and inclusion criteria were employed.
Conclusions
This review shows that the prevalence heart failure in Australia is similar to other developed countries, however it has a significant burden in specific demographic profiles in the country, namely Indigenous groups, females and those who reside in rural and remote areas. Further population-level studies, with clearly defined method of diagnosis, are needed for a more accurate description of the burden of HF in Australia.
Acknowledgements
We are grateful to DM Emdadul Hoque Department of Epidemiology and Preventive Medicine, Monash University, for his assistance in assessing the quality of the publications included in the review. This work was supported by a NHMRC Program Grant (1092642) awarded to HK and CMR. CMR is supported by a Research Fellowship from the National Health and Medical Research Council of Australia (NHMRC). The funding bodies had no role in the design and conduct of the study, the collection, management, analysis and interpretation of the data, or the preparation, review, or approval of the manuscript.
Competing interests
The authors declare that they have no competing interests.
Authors’ contribution
BWS, AJO, MPM, HK, and CMR contributed to the conception of the study, participated in writing the manuscript. BWS: performed the literature search. BWS and MMP: screened publications and selected eligible studies. All authors read and approved the final manuscript.