Incidence of stroke

Modifiable risk factors such as hypertension, diabetes, high blood lipids, and smoking are common and offer ample opportunities to alter stroke risk in large populations. -Reuters

From medical literature, there exists significant differences in stroke mortality between developed countries. Geographical variations are evident. While the average stroke mortality adjusted for average age showed a figure of 50 to100 per 100,000 people per year, the Russian Federation had a stroke mortality of more than 180 per 100,000 people per year and Canada has a figure less than 15 per 100,000. These differences may suggest a role for different frequencies of risk factors such as diabetes, hypertension, alcohol use, dyslipidemia, and smoking.

Other possible contributory factors for such differences include genetic factors and differences in the management of stroke.

In developed countries, there is evidence of a constant reduction in stroke mortality in the last 50 years. The rate of decline was 1% per year until the 1960s, when a more steep fall of 5% per year occurred. However, the trend in developing countries has been limited by the lack of data.

In developed countries, the decline of stroke mortality has been due to better control of traditional stroke risk factors such hypertension, smoking and diabetes. In addition, the general improvement in living standards also contributed. The lessons learnt for developing countries is clear.

In a community-based study in Oxford, England, the incidence of cerebrovascular events (strokes or the occurrence of mini-strokes/near-strokes was observed to be higher than heart disease or peripheral arterial disease or arterial disease affecting the lower part of the body. Stroke incidence (the rate of new strokes occurring over a definite period in time compared against the population under consideration) also varies across Europe. The incidence varies from 240 per 100,000 to 600 per 100,000, again implicating environmental and genetic factors.

A possible explanation for the above findings are methodological problems in the studies. But, on the other hand, a study in Australia also saw similar reductions in stroke incidence of 25% from the year 1989 to 1995. These reductions may be the result of improved risk factor management. In contrast, within a similar time frame, ie from 1987 to 1994, the incidence of stroke increased.

The issue of stroke prevalence or the number of patients affected with stroke at a specific point in time within an examined population has not been studied as well. It reflects the burden of disease in the community but is harder to study as it involves individually identifying such patients in a specific community. Prevalence can also be estimated with knowledge from stroke incidence and mortality as it is roughly equivalent to the number of stroke survivors.

What an increasing prevalence of stroke translates to is the fact that there will be increasing numbers of stroke survivors with decreasing stroke mortality rates. A larger number of stroke survivors will place an increasing burden on healthcare and social care systems.

References:

1. Donnan GA, Fisher M, Macleod M, Davis S. Stroke. Lancet. 2008;371:1612-23

2. Hacke W, Kaste M, Bluhmki E et al Thrombolysis with alteplase3 to 4.5 hours after acute ischaemic stroke. NEJM 359;1317-1329

Assoc. Prof. Dr Tan Kay Sin is a consultant neurologist and a full time academic staff at the Faculty of Medicine, University of Malaya where he teaches internal medicine and neurology. This article is contributed by The Star Health & Ageing Panel, which comprises a group of panellists who are not just opinion leaders in their respective fields of medical expertise, but have wide experience in medical health education for the public. The members of the panel include: Datuk Prof Dr Tan Hui Meng, consultant urologist; Dr Yap Piang Kian, consultant endocrinologist; Datuk Dr Azhari Rosman, consultant cardiologist; A/Prof Dr Philip Poi, consultant geriatrician; Dr Hew Fen Lee, consultant endocrinologist; Prof Dr Low Wah Yun, psychologist; Datuk Dr Nor Ashikin Mokhtar, consultant obstetrician and gynaecologist; Dr Lee Moon Keen, consultant neurologist; Dr Ting Hoon Chin, consultant dermatologist; Prof Khoo Ee Ming, primary care physician; Dr Ng Soo Chin, consultant haematologist. For more information, e-mail starhealth@thestar.com.my. The Star Health & Ageing Advisory Panel provides this information for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader's own medical care. The Star Health & Ageing Advisory Panel disclaims any and all liability for injury or other damages that could result from use of the information obtained from this article.

-The Star/Asia News Network