According to this new report, in high income-countries, dietary risk factors accounted for over half (55%) of the disability-adjusted life years (DALYs) lost owing to stroke.
In low- and middle-income countries, the contribution of poor diets to stroke burden was even higher, at 65.3%, with the overal global contribution calculated at 63.4%.
By comparison, tobacco smoking accounted for just under 20% of the burden of stroke in high income countries, and only 22.8% globally.
Food for thought.
"Our study provides robust evidence of the very large contribution that behavioral risk factors make to stroke burden. These risk factors are avoidable," lead author Valery L. Feigin, MD, from Auckland University of Technology, New Zealand, commented to Medscape Medical News.
"Poor diet, smoking, alcohol, lack of exercise, et cetera, are responsible for more days of stroke disability than factors such as hypertension, hyperglycemia, high cholesterol, et cetera. Our data show that stroke is definitely a disease of lifestyle, and as such a great proportion of stroke disability can be avoided. This is a new paradigm and has clear practical implications."
The other major and unexpected finding of the study is the large contribution that air pollution makes to stroke burden, Professor Feigin said.
"Our data show that air pollution is responsible for one third of stroke burden. We knew there was an association between air pollution and stroke, but we didn't expect to see such a large effect," he said. "This has not been studied before. A number of studies have looked at air pollution and risk of cardiovascular disease and seen quite strong evidence of a causal link, but in terms of magnitude of its contribution to stroke burden this is the first report."
Their findings were published online in Lancet Neurology on June 9.
The new data come from Global Burden of Disease (GBD) study, which Professor Feigin explained is the largest repository of epidemiologic studies and official statistics on medical conditions. "It is regularly updated and analyzed with sophisticated techniques so that it allows models of the burden of different diseases in each nation using all available information."
For the current analysis, the researchers estimated the disease burden of stroke associated with 17 risk factors in 188 countries. They calculated the population-attributable fraction of stroke-related disability-adjusted life-years (DALYs) for each risk factor: that is, the estimated proportion of disease burden in a population that would be avoided if exposure to a risk factor were eliminated. The study is the first to analyze the global risk factors for stroke in such detail, especially in relation to stroke burden on global, regional, and national levels.
"Our main results show that over 90% of stroke burden can theoretically be avoided by controlling risk factors," he said. "This is a highly preventable condition."
The GBD Study: A "Monumental Task"
In an accompanying comment, Vladimir Hachinski, MD, University of Western Ontario, London, Canada, and Mahmoud Reza Azarpazhooh, MD, Mashhad University of Medical Sciences, Iran, note that stroke imposes possibly the greatest burden of DALYs of all neurologic disorders.
They point out that a systematic analysis of 119 studies has shown the loss of more than 100 million DALYs related to stroke in 2010, and a significant increase since 1990, especially in low- and middle-income countries.