Stroke is the third leading cause of death and the main cause of long-term disability in Western societies.1 About 15 million people worldwide suffer from stroke annually.2 The increasing longevity of the populations in developed countries will cause far-reaching socioeconomic and social problems and seriously affect their health-care systems. This will result in the burden of diseases with an age-dependent incidence increasing markedly over the next few decades worldwide. In the 27 European Union (EU) countries, the total annual cost of stroke was estimated to be €27 billion as at 2009,3 with €18.5 billion (68.5%) for direct costs and €8.5 billion (31.5%) for indirect costs.4 An additional €11.1 billion was estimated as the cost of informal care.4 Including informal care in the total amount changes the percentage contributions of direct, indirect, and informal care costs to 48.6%, 22.3%, and 29.1%, respectively.3 However, the cost per stroke patient in Austria is difficult to estimate. The following estimates are given in EURO purchasing power parity (PPP) which is an international measure to be able to compare economic data between countries by adjusting for the relative purchasing power in the respective countries. These estimates range from EUR PPP 9,634 in 20105 to EUR PPP 20,784 in 2004.6

Population projections predict a considerable increase in the older population throughout Europe. From 2012 to 2075 the number of residents older than 75 years will increase by 70%, 75%, 91%, 104%, 153%, 161%, and 162% in Germany, Spain, Italy, France, the UK, Denmark, and Austria, respectively.7 The estimated population pyramids in Austria in 2012, 2050, and 2075 stratified by sex are illustrated in Fig. 1.

The elderly population throughout the EU is predicted to increase by 103% overall.7 This huge ageing of the population will have various consequences for the EU's health and social systems that must be addressed, especially for diseases with age-dependent incidence rates such as stroke.

Several studies have clearly demonstrated that the incidence of ischemic stroke increases with age: about 50% of strokes occur in people older than 70 years and nearly 25% of them are in people older than 85 years.8910 Combining the age dependency of stroke with the expected demographic developments stimulated us to formulate the following research question: "How will the numbers of registered patients with ischemic stroke change within the next few decades, especially with respect to their sex and age?" Hence, it is the aim of this study was to project the number of ischemic strokes recorded in the Austrian Stroke-Unit Registry from 2012 to 2075.

Two different data sources and one assumption were used to project the total numbers of patients with registered ischemic stroke into the next few decades. The information in these data sources is freely available in the public domain, and hence no informed consent, trial registration, or ethics committee approval was necessary.

The population of Austria was 8.4 million in 2012, and this is estimated to increase to 8.0 million, 9.4 million, and 11.6 million in 2075 according to the ageing, main, and growth scenarios, respectively. The total number of registered ischemic strokes was 8,690 in 2012, and is expected to increase to 15,826, 15,626, or 18,134 in 2075 according to the three scenarios. Fig. 2 provides a detailed overview of the projected numbers of patients with ischemic stroke between 2012 and 2075.

Within different age strata, the corresponding number of patients are projected to increase or decrease as follows (100%=number of patients in 2012): 0–40 years, 100%/99% (males/females); 40–50 years, 83%/83%; 50–60 years, 98%/97%; 60–70 years, 126%/119%; 70–80 years, 159%/139%; 80–90 years, 307%/199%; and 90+ years: 894%/413%. A detailed overview of these changes is presented in Table 1.

The total number of patients registered with ischemic stroke in Austria will increase to 180%, 208%, or 182% from 2012 to 2075 (100%=number of patients in 2012) according to the ageing, main, and growth scenarios, respectively; the corresponding value is 240%, 278%, or 250% in patients aged 80–90 years, and 537%, 683%, or 637% in patients aged 90+ years. These findings indicate that the perioperative costs associated with ischemic stroke due to co-morbidity, perioperative complications, and prolonged postoperative rehabilitation will increase markedly during the forthcoming decades.

The ageing population means that the patient capacity of hospitals and rehabilitation institutions will have to expand markedly or their admission strategies for patients will have to change over the coming decades. Since stroke is usually accompanied by long-term disability, the need for long life care will also increase along with the demand for places in care homes. Furthermore, evidence-based acute and postdischarge procedures are needed that aim at reducing the number of severely disabled stroke patients and eventually to further reduce costs. Such measures have already been studied in randomized controlled trials; for example, intravenous thrombolysis is highly efficacious as a treatment for acute ischemic stroke within the first 3 hours.12 Furthermore, recently reported thrombectomy studies have confirmed the efficacy of neurointervention for recanalization in strokes caused by occlusion of the large cerebral arteries.1314 A broad availability of specialized stroke centers in Austria with full ("24/7") availability of neurointerventions will lessen the burden of ischemic stroke in Austria and help to reduce health-care expenditure.

The increasing number of patients with ischemic stroke will have a major economic burden and effects on health policies in Austria. The results of this study can be used to guide discussions aimed at estimating future costs in the Austrian health system for health-care professionals.