The data, from the largest study of its kind, investigated whether consumption of diet beverages are associated with cardiovascular outcomes and mortality rates, afterprevious studies linked the consumption of diet and artificially sweetened drinks with weight gain and an increased risk of metabolic syndrome - which itself is linked to diabetes and heart disease
"We were interested in this research because there was a relative lack of data about diet drinks and cardiovascular outcomes and mortality," explained Ankur Vyas, M.D from the University of Iowa Hospitals and Clinics - who led the study.
"Our findings are in line with and extend data from previous studies showing an association between diet drinks and metabolic syndrome."
The research, which is due to be presented at the American College of Cardiology's 63rd Annual Scientific Session, shows that compared to women who never or only rarely consume diet drinks, those who consumed two or more a day were 30% more likely to suffer a cardiovascular event and 50% more likely to die from related disease.
Vyas and colleagues analysed diet drink intake and cardiovascular risk factors from 59,614 participants in the Women's Health Initiative Observational Study, making this the largest study to look at the relationship between diet drink consumption, cardiac events and death.
Information on women's consumption of diet drinks was obtained through a questionnaire that asked them to report their diet drink consumption habits over the previous three months. This information was assessed at follow-up year three of the Women's Health Initiative Observational Study. For the purposes of the analysis, researchers divided the women into four consumption groups: two or more diet drinks a day, five to seven diet drinks per week, one to four diet drinks per week, and zero to three diet drinks per month.
After an average follow-up of 8.7 years, the primary outcome – a composite of incident coronary heart disease, congestive heart failure, heart attack, coronary revascularization procedure, ischemic stroke, peripheral arterial disease and cardiovascular death – occurred in 8.5% of the women consuming two or more diet drinks a day compared to 6.9% in the five-to-seven diet drinks per week group; 6.8% in the one-to-four drinks per week group; and 7.2% in the zero-to-three per month group.
The team reported that the association between diet drink consumption and cardiovascular outcomes persisted even after they adjusted the data to account for demographic characteristics and other cardiovascular risk factors and comorbidities, including body mass index, smoking, hormone therapy use, physical activity, energy intake, salt intake, diabetes, hypertension, high cholesterol and sugar-sweetened beverage intake.
However, Vyas said the association between diet drinks and cardiovascular problems raises more questions than it answers, and should stimulate further research.
"We only found an association, so we can't say that diet drinks cause these problems," she commented, adding that there may be other factors about people who drink more diet drinks that could explain the connection.
"It's too soon to tell people to change their behaviour based on this study; however, based on these and other findings we have a responsibility to do more research to see what is going on and further define the relationship, if one truly exists," said Vyas.