Estimating the potential contribution of stroke treatments and preventative policies to reduce the stroke and ischemic heart disease mortality in Turkey up to 2032: a modelling study

Ischemic stroke and ischemic heart disease (IHD) continue to cause most cardiovascular and circulatory deaths globally, which mostly contribute to the increasing number of premature deaths, [1]. Stroke accounts for a substantial proportion of these deaths worldwide, with being the main cause of 10 % of the deaths and 4 % of the DALYs (Disability adjusted life years) in 2010, [2]. While some high-income countries show dramatic decreases in stroke incidence in the past four decades, in many low and middle income countries stroke incidence and number of stroke related deaths and DALYs are still increasing, [2, 3].

In common with other middle income countries, stroke is still one of the most common cause of deaths in Turkey. In 2013, IHD and stroke remained to be the top two causes of years of life lost (YLLs) as they were in National Burden of Study in 2000, [4, 5].

Stroke and IHD deaths are eminently preventable and acute and secondary treatments contribute to reduce mortality, however, prevention from stroke could contribute to this reduction more. Consumption of a diet with reduced sodium, increased portions of fruits and vegetables, with smoking cessation and with control of diabetes mellitus in combination with treatment of hypertension shown to prevent stroke incidence and deaths, [6]. These kind of effective interventions may require policy initiatives to support the individuals to change health behaviours or to effectively medicate them, [7]. Thus, a better understanding of the effectiveness of policy or other interventions has been an urgent need to inform ischemic stroke and IHD prevention strategies.

We, therefore, aimed to model and compare the future impact of different policy scenarios targeting to improve ischemic stroke treatment and to improve nutrition at the population level with policy interventions including smoking cessation on both ischemic stroke and IHD deaths for the next two decades.

The Ischemic Stroke Model is a Microsoft Excel cell-based Markov model, for Turkish population of 35 years and over, consisting finite number of health states reflecting the natural history of ischemic stroke. Markov Model provides estimates for future burden of CVD deaths and it can provide information for policy makers by comparing the outcomes from different intervention scenarios targeting specific risk factors and treatments [8, 9]. The model starts in 2012 and runs for 10 and 20 years. We assumed that a close cohort of individuals is free of ischemic stroke at the start of the simulation and every year the individuals can move from one health state to another. The possible pathways between heath states are shown in Fig. 1.

The main model inputs are population data, incidence and case-fatality rates of ischemic stroke. The main outcome is the total number of ischemic stroke and IHD deaths that will occur over a 10 and 20 years time horizon.

Ethical approval was not required for this model based study as we made secondary analysis of previously published, unidentified and publicly available data.

In the baseline scenario, we forecast that approximately 655,180 ischemic stroke and IHD deaths (306,500 in men; 348,600 in women) may occur in the age group of 35–94 between 2012 and 2022 and 1,150,000 ischemic stroke and IHD deaths (544,720 in men; 650,230 in women) between 2012 and 2032 in Turkey.

Figure 2 shows the estimated number of the ischemic stroke and IHD deaths that could be prevented or postponed by achievement of conservative, feasible or optimal scenarios of medical treatment and population level policy improvements in Turkey for year 2022.

This modelling study estimates the future impact of possible population level policy interventions and ischemic stroke treatment scenarios on ischemic stroke and IHD deaths in Turkey. Approximately 655000 ischemic stroke and IHD deaths may occur between 2012 and 2022 in the base scenario. The model estimates suggest that even with conservative changes in food policy approximately 60000 deaths can be prevented or postponed in 10 years time. Primary prevention and food policies especially feasible reductions in transfat and salt made the highest contribution to this health gain whereas acute and chronic care for ischemic stroke with contributing additional benefits will be unsufficient to significantly impact on future burden of stroke in Turkey.

Many of the interventions to prevent deaths from IHD and ischemic stroke constitute medical treatments and the “high-risk approach”. However there could be massive health gains by prevention of IHD and ischemc stroke deaths if population level policies were successfully implemented in Turkey.

Our study suggests that thousands of deaths could be prevented with transfat reduction at population level. This could be achieved by public campaigns food labelling and legislative policies [25]. There are exampler countries who imposed legislation on food manufacturers to limit their population’s intake of trans-fats. For example in 2003 Denmark set an upper limit for artificial trans fat levels in foods effectively banning partially hydrogenated oils. In the following years New York and Switzerland introduced legislation to limit trans fat, [26, 27]. In both Denmark and New York legislation has effectively eliminated industrial transfats; for example in New York restaurants the prevalence of use of industrial transfats has declined from 50 % to less than 2 % [28, 29]. Similarly in the UK while transfat accounted for 1.1 % of food energy in 2000 this reduced to 0.8 % of food energy in 2010 with implementation of successful legislative strategies [30]. There are also successful examples of policy interventions on industrial food labelling. In 2006 introduction of mandatory trans fat labelling in US prompted reformulation and many products are now labelled as free from transfats [25]. Although there have been discussions on effectiveness of transfat reduction strategies for example suggesting that legislative strategies have been more successful than labelling or education [28, 29] the findings of a review with data from developed countries show that the policies introduced to decrease transfat levels in food supply have been effective regardless of the intervention employed [31]. However there is sparse evidence for low and middle income countries on effectiveness of these policy strategies responses and health outcomes. Furthermore important inequalities exist with high consumption of trans fats in disadvantaged groups thus benefits in deprived communities might be larger [32]. In Turkey Turkish Ministry of Health has recently established strategic plans on transfat labeling and reformulation for the year 2017, [33]. Our findings show that the health gains of these actions will be massive in Turkey as a middle income country if effectively implemented.

Reduction of salt in populations has been a prior concern for prevention of cardiovascular diseases including IHD and ischemic stroke. The WHO Member States agreed on a voluntary global target for a 30 % relative reduction in mean population intake of salt with the aim of achieving a target of less than 5 g per day by 2025. Many countries including Japan UK Finland and Portugal have reduced population-wide salt intake in the recent years through a combination of regulations on the salt content in processed foods labeling of processed and prepared foods public education and engagement with the food industry [34]. In the UK for example salt reduction strategy started in 2004 and the adult daily salt intake decreased from 9.5 g/day to 8.6 g/day by May 2008 [30]. This was a 10 % population-reduction in salt achieved over 4 years without reduction in sales of the products and without consumer complaints about taste [35]. In Finland and Japan 6 g/day reduction was achieved with specific legislation [34]. Likewise in most developed countries a reduction in salt intake could be achieved by reduction in the amount of salt added to food by the industry. However in some countries public health campaigns might be needed to raise awareness of population where most of the salt comes from salt added during cooking [34]. In Turkey for example where 30 % of daily salt consumption comes from bread a 3 gr/day salt reduction (from 18gr/day to 15gr/day) was achieved between 2008 and 2012 both with health campaings and legislation on the amount of salt in bread [23]. Our estimates suggest that with continuation of the achievements in salt reduction at population level even with conservative reductions thousands of IHD and ischemic stroke deaths could be saved in the following two decades.

Our study also suggests that substantial number of IHD and ischemic stroke deaths could be prevented by increasing fruit and vegetable consumption at population level. Although Turkey produces and exports fruit and vegetable the consumption of fruit and vegetable shows a decreasing trend [36] and dietary patterns differ substantially between regions and income groups. Income level and lack of knowledge about healthy nutrition are the main determinants of nutrition patterns in Turkey, [37]. Therefore for low-income groups which suffer the highest burden of IHD and stroke the benefit might even be higher with an increase in daily consumption of fruit and vegetables.

The stroke and cardiovascular disease burden like other low and middle income countries is increasing in Turkey. This public health epidemic requires immediate action. Our analysis suggests that effective and evidence-based food policies at the population level could massively contribute through a 20 % reduction in ischemic stroke and IHD mortality in a decade and deliver bigger gains compared to healthcare based interventions for primary and secondary prevention. Results of previous modelling studies [42, 43] for prevention of cardiovascular diseases have been utilising by the governments and WHO [44, 45]. Turkish Ministry of Health also has policy documents and action plans to reduce the burden of noncommunicable diseases with effective prevention at national level [46, 47]. We particularly used these targets for simulation of scenarios for the next 10 years. Our modelling study can be a useful tool to explore potential benefits of implementing certain strategies for prevention of ischemic stroke and heart diseases in the future. Further studies that include economic analysis of different interventions are needed to compare the cost effectiveness of future scenarios in order to target and implement the best interventions.