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Keywords:

  • ethnic disparities;
  • prevention;
  • risk factors;
  • stroke

Abstract

  1. Top of page
  2. Abstract
  3. References

There are approximately 45 000 stroke survivors in New Zealand and this number is projected to increase to 50 000 survivors, with annual costs to the health system exceeding $700 million by 2015 if no effective primary stroke prevention strategies are introduced. However, development of evidence-based stroke prevention strategies requires answering several research questions. In this article, we summarize some key research questions that are particularly pertinent to stroke prevention in New Zealand.

The most recent Global Burden of Diseases, Injuries, and Risk Factors Study (the GBD 2010 Study) estimates ranked stroke as the number 2 cause of death [1] and the number 3 cause of disability-adjusted life years [2] (DALYs) in the world. Stroke incidence is increasing in low- and middle-income countries in contrast to high income countries where a 42% decline in incidence has been seen over the last four decades [3]. Of particular concern to New Zealand (NZ) is that the age-adjusted stroke incidence rate in NZ is second highest amongst developed countries [3]. Moreover the rate of decline is almost four times slower than in other developed countries. The incidence rates of stroke in Māori and Pacific people in NZ over the last two decades have increased [4]. Stroke burden on families and society is projected to rise from ≈38 million DALYs lost globally in 1990 to 61 million DALYs in 2020 [5] due to population ageing. There are approximately 45 000 stroke survivors in NZ [6] and this number is projected to increase [6] to 50 000 survivors [7] with annual costs to the health system exceeding $700 million by 2015 if no effective primary stroke prevention strategies are introduced. However, development of evidence-based stroke prevention strategies requires answering several research questions. Below we summarize some key research questions that are particularly pertinent to stroke prevention in NZ.

Health inequalities between socioeconomic and ethnic groups are a key public health concern [8, 9]. There are notable ethnic disparities in stroke incidence and outcomes in NZ [4, 6, 9] and elsewhere [10], with Māori and Pacific people having consistently higher stroke incidence rates and worse functional outcomes compared with NZ Europeans [4, 11, 12]. Also, while age-adjusted stroke incidence rates declined in NZ Europeans/Pakeha between 1981–2003 by 19%, in Māori and Pacific people these increased by 19% and 66% for the same period, respectively [4, 11]. Reasons for this disparity remain unclear. The observed ethnic/racial difference in the risk of stroke cannot be explained by only socioeconomic differences, suggesting underlying ethnic/racial differences in the relative significance and prevalence of stroke risk factors, and possibly their particular interactions (including gene-environment interactions). The only large (n = 3489) stroke case-control study in NZ [13] was based on the 1991–1992 Auckland stroke cohort but it analyzed all stroke subtypes combined, and did not examine any novel biological/psychological risk factors. Moreover the study was not designed to examine the causes of ethnic disparities in the risk of IS and PICH in NZ. The independent contribution of each risk factor to the burden of stroke in NZ – the population-attributable risk (PAR) – is also unknown. Yet, an understanding of the risk factors for stroke and stroke sub-types (including their population attributable-risks) in different ethnic populations is crucial to determine priorities and strategies for targeted stroke prevention in these populations [14, 15] and reversing the increasing rates of IS and PICH incidence rates in Māori and Pacific people of NZ [4]. There is also lack of understanding of causes of two to three times greater risk of ischemic stroke and primary intracerebral hemorrhage in Māori and Pacific people compared with European New Zealanders [4]. Is it possible that the prevalence and/or strength of association of risk factors for these strokes in Māori and Pacific people are significantly different from that in European New Zealanders? Are some genetic or particular gene–environment interactions playing a role in these differences? Answering these questions will inform developing more specific, culturally adequate primary stroke prevention interventions in our country to reduce the risk of stroke in our country. Accurate population-based data on determinants of the risk of stroke in Māori, Pacific Islanders and NZ Europeans will also facilitate implementation of evidence-based recommendations to bridge gaps in health services and increase uptake of lifestyle changes and primary stroke prevention in our country [16].

Primary stroke prevention is undoubtedly a mainstream strategy to reduce stroke burden in a population [17]. Although stroke and coronary heart disease (CHD) share many common risk factors and an integrative approach is required for primary prevention of these and other major non-communicable disorders, etiologically stroke is far more diverse [18, 19] than CHD. Various stroke subtypes have varying etiologies and require different prevention strategies [18-21]. There is evidence that, compared to CHD, traditional risk factors (e.g. elevated blood pressure, elevated cholesterol level) appear to exert different magnitudes of risk for stroke and within stroke subtypes [14]. The lack of robust evidence on relative significance of various determinants of stroke occurrence in our population may be one of the contributing factors of the observed almost four times lower reduction of stroke incidence in NZ compared to other developed countries over the last three decades [4, 11].

Another important but yet under-researched issue of stroke prevention in NZ is public education. Effective community-based educational and preventive programs require an accurate assessment of the baseline knowledge of cardiovascular disease (CVD) risk factors and symptoms in a population. While there are numerous CVD and stroke prevention programs in NZ and several reports on the relationship between CVD and a range of other relevant variables, such as socio-economic inequalities [22, 23] there appears to have been little research in NZ on public awareness of and knowledge about CVD and stroke. A recent survey of NZ' Health-covered personal experiences of ischemic heart disease and stroke [24], but did not include public awareness or knowledge of relevant risk factors or signs and symptoms. However, there is accumulating evidence that increased public health awareness about stroke and other CVD warning symptoms and risk factors facilitates primary stroke prevention and is associated with positive trends in stroke occurrence and outcomes [25-31]. Therefore, identifying gaps in knowledge about stroke and CVD warning symptoms and risk factors in major ethnic groups would inform future culturally appropriate interventions for community-based educational preventative programs in our country. Existing evidence suggests that for a stroke education program to be effective in minority ethnic groups it should be based on a prolonged engagement with local communities, include self-management component and be cultural sensitive [32].

Finally, new effective and affordable primary stroke prevention strategies that would take into account the multi-cultural nature of the NZ population are urgently required. An important recommendation of the current NZ Guideline The Assessment and Management of Cardiovascular Risk is that people at more than 10% 5-year CV risk should receive individualized advice on healthy lifestyle modifications (including a cardioprotective diet, regular physical activity and smoking cessation if relevant) using motivational interviewing techniques relating to smoking cessation. For people at greater than 15% 5-year CV risk, in addition to lifestyle interventions, these guidelines recommend aspirin, blood pressure lowering medication and lipid modifying therapy (statins). However, the large majority of such New Zealanders are not benefiting from these therapies and no motivational interviewing technique has been proven to be effective for these interventions. For example, in 2005, of the 2·09 million people aged over 35 years in NZ, over 30% of people (632 000) were at moderate (CVD risk 10–15% in 5 years) to high (CVD risk 15%+ in 5 years) risk of CVD development or suffer from CVD (heart attack, stroke or angina) [33]. However, only 10% of those with 5-year CVD risk between 10% and 14%, and only 16% of those with 5-year CVD risk 15%+ had received blood pressure lowering and lipid-lowering therapy according to the NZ Guidelines for CVD prevention [34]. Low adherence to recommended medications and healthy lifestyle modifications has been identified as the main obstacle for effective primary cardiovascular disease prevention [35-37].

In summary, we identified the most critical research questions that need to be answered to advance stroke prevention and reduce stroke burden in NZ and internationally. To address all these issues, a coherent and long-standing program research on stroke prevention in NZ is warranted.

References

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  2. Abstract
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