Compared to women who never or seldom consume diet drinks, those who drank two or more a day were 30 percent more likely to suffer a cardiovascular event and 50 percent more likely to die from related disease, researchers found.
The findings were gleaned from an analysis of diet drink intake and consequences among almost 60,000 participants in the Women's Health Initiative, a long-running U.S. observational study of cardiovascular health trends among postmenopausal women.
"Our findings are in line with and extend data from previous studies showing an association between diet drinks and metabolic syndrome," said Dr. Ankur Vyas of the University of Iowa Hospitals and Clinics, lead investigator of the study. The syndrome is associated with a cluster of risk factors for heart disease, including high blood pressure, high cholesterol and weight gain.
Results of the study were presented at the annual scientific sessions of the American College of Cardiology, in Washington.
The average age of women in the diet drink study was 62.8, and they had to have had no history of cardiovascular disease to be included in the analysis.
Through a questionnaire, the women were asked to report their diet drink consumption over the previous three months. A drink was defined as a 12-ounce beverage and included both diet sodas and diet fruit drinks.
After an average followup of 8.7 years, a combination of negative outcomes including coronary heart disease, congestive heart failure, heart attack, ischemic stroke, peripheral arterial disease and cardiovascular death were seen in some 8.5 percent of women who consumed two or more diet drinks a day.
That compared with 6.9 percent of women who had five to seven drinks per week, 6.8 percent having one to four drinks per week, and 7.2 percent in those having zero to three diet drinks per month.
"We only found an association, so we can't say that diet drinks cause these problems," Vyas said, adding that other factors may explain the apparent connection between diet drink consumption and risk of heart attack and stroke.
For instance, he noted that women who consumed two or more diet drinks per day were younger, more prone to be smokers, and had a higher prevalence of diabetes, high blood pressure and of being overweight.
Vyas said more studies are needed to more closely assess the risk of diet sodas and cardiovascular risks, if such a connection actually exists.
Previous studies have suggested a connection between artificially sweetened drinks and weight gain in adults and teens, and a likely increase in metabolic syndrome.