"The risk of coronary heart disease conferred by diabetes is between 40% to 50% greater for women than for men," said study co-author Rachel Huxley, director of the Queensland Clinical Trials and Biostatistics Centre at the University of Queensland in Australia.
The results support findings from an earlier analysis that found that women with diabetes have a nearly 50% increased risk of death from heart disease compared to men with diabetes, the study authors said.
Women at worse starting point
This difference could stem from the fact that men develop full-blown type 2 diabetes earlier than women and at a lower weight, Huxley said. Because of this, men receive aggressive treatment sooner both for their diabetes and potential heart health risks, such as high blood pressure or elevated cholesterol levels.
Meanwhile, women may have to deteriorate further than men before full-blown type 2 diabetes develops, so they're at a worse starting point even before treatment begins. The study authors cited data that show the body mass index (BMI) of women at the time of their diabetes diagnosis tends to be nearly two units higher than it is in men. BMI is a score that measures if a person is considered overweight in relation to their height.
"It is not so much that women are not being treated, it is more that they are further along when they are diagnosed," said Dr Mary Ann Bauman, medical director for Women's Health and Community Relations at Integris Health in Oklahoma City, and a spokeswoman for the American Heart Association.
The study authors reviewed health data on more than 850 000 people gathered from 64 different studies conducted between 1966 and 2013. The new report was released online in the journal Diabetologia.
Although the studies didn't identify what type of diabetes the study volunteers had, type 2 diabetes is by far the most common type of diabetes, according to the American Diabetes Association.
Nearly 30 000 people in the studies had some form of heart disease, the study authors noted.
When the researchers looked at the risk by gender, they discovered that diabetic women were nearly three times more likely to develop heart disease than women without diabetes. For men with diabetes, the risk of heart disease was slightly more than twice as likely compared to men without diabetes.
Although the study found an association between women with diabetes and heart disease, it doesn't prove a cause-and-effect relationship between diabetes, gender and heart disease.
The study findings do strongly suggest that doctors need to consider gender when treating chronic disease, said Dr Tara Narula, associate director of the Cardiac Care Unit at Lenox Hill Hospital in New York City.
"The days of lumping men and women together are coming to an end," Narula said. "We need to see women as unique entities regarding their risk factors and, if we recognise there's this gender differential, we need to be more aggressive in screening and treating women for diabetes or heart disease."
Resistance to insulin
Women likely need to receive more aggressive treatment while in pre-diabetes, rather than waiting for full-blown diabetes to develop, both Narula and Bauman said. In pre-diabetes, people have started to build up resistance to insulin but do not have the high blood sugar levels needed for a diagnosis of diabetes.
It may be that spending a longer period of time in pre-diabetes takes a toll on the blood vessels of the heart, causing them to harden and narrow, they said.
"If that turns out to be true, then we might need to look more in the pre-diabetic phase, to maybe be more aggressive than we already are," Bauman said. "We can keep these things from happening. Heart disease is largely preventable."
The study authors recommend increased screening for pre-diabetes in women, as well as more stringent follow-up of women at high risk of diabetes.