The more education a person has, the lower the heart and stroke risk, U.S. researchers say, at least in high-income countries.

This may not be entirely true in the case of women though. A study published in Journal of the American Heart Association finds highly educated women in low- and middle-income countries had a slight increase in the incidence of fatal and non-fatal heart attack and stroke. Higher smoking rates in women with greater education levels in low-, middle- and high-income regions may be the reason, the study says.

Smoking typically declines as formal education rises, but nearly half of the highly educated women from high-income countries smoked, compared with 35 percent for those with the least amount of schooling, the researchers say.

In low- and middle-income countries, the smoking rate is 21% among the most-educated women as against 14% among the least educated.

In men, there was no change in smoking rates across educational groups in low- and middle-income countries. In richer countries, the most-educated men smoked less than did men with the fewest years of formal education.

We can't assume that just because certain groups are more educated than others that they're going to have healthier lifestyles, the lead author, Dr. Abhinav Goyal of the Emory School of Medicine in Atlanta, said in a statement.