People who live in low-to-middle income countries face a greater risk of stroke than those living in wealthier nations. A new study published in the British journal The Lancet Neurology finds that common risk factors often associated with stroke do not explain the global discrepancies.
Claiborne Johnston, neurology professor at the University of California San Francisco and the lead author of The Lancet study, says stroke is not a disease exclusive to wealthy countries.
"The perception has been that stroke is a disease of high-income countries of the developed world and isn't a concern in lower-income countries, and our study suggests that the opposite should be the case," he says.
Stroke is second only to heart disease among the world's deadliest killers and accounts for 10 percent of all deaths worldwide, with the greatest burden in Eastern European and North Asia and more recently in Central Africa and the South Pacific. Those rates, Johnston says, are 10-times those in the United States, Switzerland or Israel.
To help explain the difference, estimates were calculated from World Health Organization data for common risk factors like hypertension, obesity, diabetes, smoking and alcohol abuse. With the exception of binge drinking, none explained the higher stroke incidence in low-to-middle income countries.
Johnston suggests while some of the data may be incomplete or inaccurate, access to health care also divides richer nations from poorer ones.
"For example, in the U.S. it may be required that somebody be put on a breathing machine for a while after their stroke. That's not an option in a low-income country."
And, Johnston adds, other health factors could be at play for which no reliable measures now exist.
"We know that some infectious diseases are associated with a greater risk of stroke, in particular rheumatic fever. We don't have any measures of rheumatic fever or rheumatic heart disease in populations, and there are probably other factors that we don't know about that are also contributing to differences in stroke incidence and that also require more study."
But Johnston says financial resources have not been directed to prevent or treat stroke in poor-to-middle income countries, in part because the condition has not been considered a public health priority.