Middle-aged men still have higher rates of heart attacks and heart disease than middle-aged women, but those gender differences appear to be narrowing, according to a study published Monday.

The findings follow earlier research, published in a 2007 issue of the journal Neurology, establishing that stroke prevalence among women ages 45 to 54 was double that of men of the same age. Together, the findings suggest “an ominous trend in cardiovascular health among midlife women,” said the lead author of both studies, Dr. Amytis Towfighi, an assistant professor of neurology at the University of Southern California.

Women have been thought to be largely protected from heart attacks and stroke before menopause because of hormonal influences. But the rising rate of obesity, which is higher in middle-aged women than middle-aged men, could undermine that natural benefit.

The new study, published in the Archives of Internal Medicine, examined national survey data from 1988 through 1994 and from 1999 through 2004. More than 4,000 men and women, ages 35 to 54, completed the surveys. Researchers looked at heart attack rates as well as scores from a measure used to predict the risk of a having a heart attack in 10 years. This risk-assessment tool includes factors such as age, cholesterol levels, blood pressure and smoking history.

In both time periods, men had more heart attacks than women. But the rates of men improved from 2.5 percent in the earlier period to 2.2 percent in the second time frame while women’s rates increased from 0.7 percent to 1 percent.