Diabetes Boosts Stroke Risk in Women, But Not Men

Diabetes mellitus (DM) appears to increase the risk of stroke in women, but not in men, according to a new study.

"Several mechanisms could explain why diabetes has a greater adverse effect in women than in men. In the general population, higher numbers of strokes occurring among women than men is at least partly attributed to the longer life expectancy of women," stated lead author Wenhui Zhao, MD, of the Pennington Biomedical Research Center in Baton Rouge, LA.

"Some studies have suggested that the sex difference in cardiovascular risk is mediated in large part by differences in the levels of cardiovascular risk factors because women with diabetes have significantly higher levels of blood pressure and lipids than men with diabetes,” she said. “Others suggested that the greater risk associated with diabetes seen in women may reflect a treatment bias that favors men.”

Dr Zhao noted that recent studies found that men with DM or established cardiovascular disease are more likely to receive aspirin, statins, or antihypertensive drugs than women.

The researchers prospectively investigated the sex-specific association of different levels of hemoglobin A_1c (HbA_1c) with incident stroke risk among nearly 11,000 men and more than 19,000 women with type 2 DM. During an average follow-up of 6.7 years, nearly 3000 cases of stroke occurred among the patients.

Depending on their blood sugar control, women with DM were 19% to 42% more likely to have a stroke than those without DM. The researchers also found that the risk of stroke among women with DM was much higher for those aged 55 years and older, compared with younger women. No association between DM and stroke risk was found in men.

Referring to the increased risk of stroke in women with DM aged 55 years and over, the researchers suggest that poor blood glucose control is more harmful in older women than in younger ones.

“The possible explanation may point to the role for estrogen,” they stated. “After onset of menopause, when estrogen levels decline, the incidence of cerebrovascular disease in women increases. Preclinical studies have indicated that estrogen is neuroprotective and reduces stroke infarct volume, but clinical trials failed to show the benefit. There is a need for more research to clarify this association."

The lack of an association between HbA_1c and stroke risk in men with type 2 DM could be the result of men with higher HbA_1c values dying of coronary heart disease, rather than having a stroke, they noted.

“Diabetes poses a substantially greater increase in the risk of stroke among women than among men, which merits further investigation,” the researchers stated. “This graded positive association was more significant in women 55 years and older than in women younger than 55 years. Females with type 2 diabetes, especially postmenopausal females, are at high risk for stroke. More aggressive blood sugar treatments and better control of other risk factor levels in women with diabetes are likely to substantially reduce stroke in this subgroup.”

The researchers published their results in the February 24, 2014, issue of Diabetologia.