Long-term antibiotic use linked to greater risk of MI, stroke in women

Antibiotic use—particularly regimens that last for two months or more—was linked to an increased risk of CVD in a recent study of nearly 36,500 older women.

Lead researcher Lu Qi et al.’s work, published in the European Heart Journal April 24, focused on the relationship between women’s heart health and antibiotics, which can significantly alter the micro-environment of a patient’s gut and increase their susceptibility to disease, including CVD. Since antibiotics inevitably wipe out “good” probiotic bacteria alongside the bad, they leave the gut vulnerable to outside viruses, bacteria and potentially harmful microorganisms.

“Antibiotic use is the most critical factor in altering the balance of microorganisms in the gut,” Qi, an adjunct professor at the Harvard T.C. Chan School of Public Health, said in a release. “Previous studies have shown a link between alterations in the microbiotic environment of the gut and inflammation and narrowing of the blood vessels, stroke and heart disease.”

Qi and colleagues’ study population of 36,429 women over 60 was drawn from the Nurses’ Health Study, an ongoing effort in the U.S. since 1976. The women involved, all of whom were medical professionals themselves, self-reported their use and duration of use of antibiotics when they were younger (20-39 years old), middle-aged (40-59 years old) and older (60 and up).

Women completed questionnaires for Qi et al.’s research every two years for an average follow-up of eight years. By the time the study wrapped, 1,056 participants—around 3% of the total pool—had developed cardiovascular disease.

After adjusting for age, sex, race, diet, lifestyle and other medication use, the research team found women who used antibiotics for periods of two months or longer in late adulthood were 32% more likely to develop CVD than their counterparts who didn’t use antibiotics. Women who reported taking antibiotics for at least two months in middle age saw a 28% increased risk.

“By investigating the duration of antibiotic use in various stages of adulthood we have found an association between long-term use in middle age and later life and an increased risk of stroke and heart disease during the following eight years,” Yoriko Heianza, a research fellow at Tulane University and an author on the paper, said in the release. “As these women grew older they were more likely to need more antibiotics, and sometimes for longer periods of time, which suggests a cumulative effect may be the reason for the stronger link in older age between antibiotic use and cardiovascular disease.”

The most commonly identified reasons for taking antibiotics at any point were respiratory infections, urinary tract infections and dental problems.

The authors said their study was observational and had some inherent limitations, including the fact that patients self-reported their data and results can’t be extrapolated to men or younger women. They said they didn’t find any increase in CVD risk with antibiotic use in women who were in their twenties and thirties.

“Our study suggests that antibiotics should be used only when they are absolutely needed,” Qi said. “Considering the potentially cumulative adverse effects, the shorter time of antibiotic use, the better.”