Strokes are increasingly killing younger people, especially in developing countries where unhealthy lifestyle habits have taken hold, according to a study funded by the Bill & Melinda Gates Foundation.
While strokes are usually thought to afflict older people, the number of people ages 20 to 64 who experience them has risen by 25 percent in the past two decades, according to researchers from countries including the United States, Britain, and Japan. This younger group now makes up 31 percent of total strokes, compared with 25 percent before 1990, the study found.
Strokes are claiming more lives and leading to more illness in low-to-middle-income countries, the researchers wrote Thursday in The Lancet medical journal. As income levels in these countries rise, fewer people die of infectious diseases related to poverty, they said. However, the risk of developing chronic illnesses such as heart disease increases, they said.
‘‘While people tend to live longer as the risk of infectious diseases decreases, they are suddenly exposed to these unhealthy lifestyles in which they consume too much salt, don’t exercise, and frequently smoke,’’ Myles Connor, a professor at the University of Edinburgh and a co-author of the study, said in a telephone interview.
Stroke occurs when a blood vessel carrying oxygen to the brain ruptures or is blocked by a blood clot or some other particle, cutting off the brain’s supply of oxygen. Nerve cells then die, affecting the part of the body they control. These cells are not replaced, leading to disability, according to the World Health Organization. About 15 million people worldwide have strokes each year, of which 5 million die and another 5 million are permanently disabled, the WHO said.
The study shows the challenge posed to developing nations from Brazil to South Africa, where obesity and diabetes rates are increasing as millions emerge from poverty only to grapple with a lack of information that leads to poor lifestyle choices.
‘‘The report reveals a shocking disparity between rich and poor, where death rates from stroke are up to ten times higher in lower-income countries,’’ said Jon Barrick, chief executive of the London-based Stroke Association. ‘‘At least half of strokes could be prevented if people made simple lifestyle changes, such as keeping blood pressure under control and exercising more.’’
While the study focused on stroke trends across ages and geographical locations and not the reasons behind the trends, the authors said unhealthy diets, high blood pressure, obesity, physical inactivity, and smoking are probably leading to the rise of strokes among the young in poorer countries.
Obesity and excessive weight put a strain on the entire circulatory system, tending to raise cholesterol, blood pressure, and diabetes risk — all of which can increase the risk of stroke.
In high-income nations, reductions in the incidence of stroke and premature death rates over the last 20 years ‘‘probably reflect improved education, prevention and care, and diagnosis,’’ the researchers said. That suggests that education among the elderly can lower stroke rates.
‘‘The worldwide stroke burden is growing very fast and there is now an urgent need for culturally acceptable and affordable stroke prevention, management and rehabilitation strategies,’’ Valery Feigin, a professor at the Auckland University of Technology and co-author of study, said in a statement.