Although the researchers, whose work appeared in the Journal of General Internal Medicine, found that older adults who drank diet soda every day were 44 percent more likely to suffer a heart attack, their research did not prove that the sugar-free drinks alone were to blame.
There may be other things about diet-soda lovers that explain the connection, said lead researcher Hannah Gardener, of the University of Miami Miller School of Medicine, and her team.
"What we saw was an association. These people may tend to have more unhealthy habits," she said.
She and her colleagues tried to account for that, noting that daily diet-soda drinkers did tend to be heavier and more often have heart risk factors such as high blood pressure, diabetes and unhealthy cholesterol levels.