Stroke is a leading cause of death and disability. But can stroke be prevented? Probably not totally, but it sure is possible to drastically reduce the odds of having a stroke. A huge international study on the risk factors for stroke recently published in The Lancet has shown that the majority are potentially modifiable behaviors.
The study was carried out between 2007 and 2015, with over 13000 patients with acute first stroke (and a similar number of healthy controls) being recruited in 32 countries across Asia, America, Europe, Australia, the Middle East, and Africa. This study also assessed how risk factors vary between stroke subtype, throughout the world, and according to age or sex.
Overall, it was established that over 90% of the worldwide risk of stroke can be attributed to only ten risk factors: hypertension, low physical activity, high apolipoprotein (Apo)B/ApoA1 ratio (predictor of coronary heart disease risk), diet, abdominal obesity, psychosocial factors, current smoking, cardiac causes, alcohol consumption, and diabetes. Of these, hypertension was identified as the most important risk factor for stroke.
Some risk factors were shown to be predominantly associated with a subtype of stroke. Hypertension, although highly risky for both subtypes, was more associated with cerebral hemorrhage; smoking, diabetes, apolipoproteins, and cardiac causes, on the other hand, were more associated with ischemic stroke.
These risk factors were consistent across world regions, sex, and age groups. Still, some sex differences were observed: abdominal obesity and cardiac causes were associated with larger odds in women than in men, while the risk associated with smoking and alcohol intake was greater among men than in women, but in this case it was most likely due to the higher prevalence of smoking and drinking in men. Age differences were also found: hypertension, abdominal obesity, and cardiac factors increased the odds of stroke in younger individuals, whereas diet had a stronger association with stroke in older adults.
Overall, the combined contribution of these ten risk factors to stroke risk was consistent in all populations, but there were some interesting regional variations in the importance of individual risk factors, providing an indication of how lifestyle and cultural behaviors define the impact of each risk factor. In fact, the most remarkable conclusion to be taken from this data is that all of the major risk factors for stroke can be potentially modified by lifestyle changes.
Dietary changes are the most obvious target in stroke prevention. A healthy diet can help reduce hypertension, the most important risk factor for stroke, the ApoB/ApoA1 ratio, which indicates the relative levels of bad and good cholesterol, abdominal obesity, and diabetes.
Indeed, a healthier diet was associated with a lower risk of stroke in most regions. However, there was an interesting finding that highlights how there can be misconceptions on what a healthy diet is. A “healthier diet” did not reduce the risk of stroke in of south Asia and Africa; in fact, in south Asia, a seemingly healthier diet seemed to even be associated with an increased risk of stroke. This seems counterintuitive, but it is actually most likely due to not-so-healthy options in south Asian diet. For example, the combined intake of fruit and vegetables in south Asia is lower than in other regions. Even though a large proportion of the population in south Asia is vegetarian (about 40%) and the consumption of vegetables is very high, recent studies have shown that south Asia has one of the lowest intakes of fruit in the world, that there has been a decrease in the consumption of whole plant foods, and that there is a high use of hydrogenated vegetable oil-based ghee in cooking, which is not that healthy.
Regardless of regional differences, keeping in mind that the ten risk factors mentioned above account for around 90% of the risk of having a stroke, what stands out in this study is that stroke can be largely prevented by modifying behaviors.
And it’s not only diet that can be changed. Given the tremendous impact of hypertension, a great reduction in the occurrence of stroke may be achieved through control of blood pressure. Regular exercise can obviously counterbalance the effects of physical inactivity as well as contribute to metabolic improvements. Moderate alcohol intake and quitting smoking are also obvious actions towards stroke prevention.
O’Donnell MJ, et al (2010). Risk factors for ischaemic and intracerebral haemorrhagic stroke in 22 countries (the INTERSTROKE study): a case-control study. Lancet, 376(9735):112-23. doi: 10.1016/S0140-6736(10)60834-3
O’Donnell MJ, et al (2016). Global and regional effects of potentially modifiable risk factors associated with acute stroke in 32 countries (INTERSTROKE): a case-control study. Lancet, 388(10046):761-75. doi: 10.1016/S0140-6736(16)30506-2
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