Cardiovascular risk and gender
Dr. Doreen Rabi's research could help improve the cardiovascular health of women with diabetes.
Story by Laura Ly/Illustration by Laura Bifano
People with diabetes have a higher than average risk of developing heart disease. Following a diagnosis of diabetes, women experience a greater risk increase for cardiovascular disease than men. Why are women more susceptible to the negative effects of diabetes than men? University of Calgary researcher Dr. Doreen Rabi aims to find out.
"Diabetes—in particular type 2 diabetes—is associated with a number of metabolic changes that increase a patient's risk for heart disease, especially high blood pressure and high cholesterol," explains Dr. Rabi. However, that risk increase is greatest for diabetic women. "At any given age, men are more likely to develop heart disease than women. But when women become diabetic, they have a fourfold increase for heart disease relative to non-diabetic women. In comparison, men have only a twofold increase in cardiovascular risk associated with diabetes."
What makes diabetic women more vulnerable to heart disease? Hormonal differences, especially in post-menopausal women, could be a possible reason. "It could be a purely biological interaction between a woman's hormonal and metabolic environment that puts her at higher risk," suggests Dr. Rabi.
However, Dr. Rabi thinks a systematic difference between how diabetic men and women are treated for heart disease is a more likely explanation. "Men are more likely to be involved in clinical trials because they're more likely to have heart disease. Most cardiovascular studies enroll about 75% men and 25% women, so the data on drug efficacy in cardiovascular disease is largely from a male population. There's an assumption that these drugs behave the same in both genders, but these drugs could work very differently in women."
Dr. Rabi is reviewing published cardiovascular drug trials to identify whether certain drugs are more effective according to a patient's gender. By separating the data on men and women, Dr. Rabi hopes to identify factors that might explain the increased risk of cardiovascular disease in diabetic women. "Pre-menopausal women have much lower rates of heart disease than men, so there may be a tendency to underestimate the cardiovascular risk in women until they're older. The data show that men are consistently treated for cardiovascular disease throughout their lifespan, but treatment rates for women increase after menopause. This suggests that younger women are treated at lower levels than men. I'm trying to determine if a tendency to under treat women early for heart disease has a negative impact later," explains Dr. Rabi.
In addition, certain heart medications are unsafe for women to use during pregnancy and lactation and might be withheld by physicians during pre-conception or pregnancy. Dr. Rabi is looking at how treatment during a woman's reproductive years affects her cardiovascular risk.
She also looks at whether different adherence to medication schedules is a factor. "It's fair to say there are different demands on men and women in terms of their time and personal priorities. Women tend to prioritize the treatment of family before themselves, so it's possible that women may not adhere to medication as strictly as men because of these competing demands," notes Dr. Rabi. "The goal of this study is to determine whether our current practice of treating men and women with one treatment strategy is appropriate or whether we should have sex-specific guidelines for preventing heart disease."
As an endocrinologist, Dr. Rabi provides care to women with diabetes and who are pregnant. In her clinic, she interacts with diabetic women who are planning to have children—an interaction that gives insight into her research. "I often see women in the clinic who want to start a family but have to balance that desire with their long-term risk of heart disease. My role is to educate women about their options in minimizing cardiovascular risk. Physicians need to maintain an ongoing discussion with female patients to ensure that their hearts are protected in a timely fashion."
Dr. Rabi hopes her research will help improve how gender-specific data is reported in clinical trials. "My research looks at the quality of data we have on men and women in clinical trials. I've discovered that the quality of sex-specific reporting is surprisingly poor given the burden of heart disease. I'm hoping my research will emphasize the importance of reporting differences in characteristics and outcomes in clinical trials by gender," says Dr. Rabi.