New research suggests that side effects of long-term antibiotics use may place older women at risk of heart problems and heart-related death.

In a study presented at the American Heart Association’s Epidemiology and Prevention, Lifestyle and Cardiometabolic Health Scientific Sessions last week, researchers from Tulane University warn that the risk of death from heart disease, and from death in general, appears to increase in women over 60 when they take antibiotics for two months or longer.

Researchers looked at data on more than 37,000 women age 60 and older, classifying them on how long they took antibiotics. The women were grouped into classifications including those who did not use antibiotics at all, those who used them for less than 15 days, from 15 days to less than two months, and from two months or more, from 2004 through June 2012.

According to the findings, women who took antibiotics for longer than two months had a 27% higher risk of death from all causes, compared to women who used no antibiotics at all. They also faced a 58% higher risk of cardiovascular death. The risk of death from all causes was even higher if the women reported having taken antibiotics from ages 40 to 59 years.

The researchers noted that previous studies indicate that antibiotic use was linked to changes in gut microbes, which may be playing a factor in the increased risk of death.

“Gut microbiota alterations have been associated with a variety of life-threatening disorders, such as cardiovascular diseases and certain types of cancer,” study author Dr. Lu Qi, professor of epidemiology at Tulane University, said in an American Heart Association press release. “Antibiotic exposure affects balance and composition of the gut microbiome, even after one stops taking antibiotics; so, it is important to better understand how taking antibiotics might impact risks for chronic diseases and death.”

Qi noted that while the association was notable, the findings do not prove that antibiotic use caused the deaths. He noted that women who took long-term antibiotics may just be less healthy than those who do not. Until the results are published in a peer-reviewed journal they are considered preliminary.