Among middle-aged and older women, 2 or more months’ exposure to antibiotics is associated with an increased risk of coronary heart disease or stroke, according to a study in the European Heart Journal.

Risk of cardiovascular disease according to duration of antibiotic use in different phases of adulthood. European Heart Journal and Professor Lu Qi, Tulane University, USA

Women in the Nurses’ Health Study who used antibiotics for 2 or more months between ages 40 and 59 years or at age 60 years and older had a significantly increased risk of cardiovascular disease, compared with those who did not use antibiotics. Antibiotic use between 20 and 39 years old was not significantly related to cardiovascular disease.

Prior research has found that antibiotics may have long-lasting effects on gut microbiota and relate to cardiovascular disease risk.

“Antibiotic use is the most critical factor in altering the balance of microorganisms in the gut,” said lead investigator Lu Qi, MD, PhD, in a news 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,” said Dr. Qi, who is the director of the Tulane University Obesity Research Center in New Orleans and an adjunct professor of nutrition at Harvard T.C. Chan School of Public Health in Boston.

To evaluate associations between life stage, antibiotic exposure, and subsequent cardiovascular disease, researchers analyzed data from 36,429 participants in the Nurses’ Health Study. The women were at least 60 years old and had no history of cardiovascular disease or cancer when they completed a 2004 questionnaire about antibiotic usage during young, middle, and late adulthood. The questionnaire asked participants to indicate the total time using antibiotics with eight categories ranging from none to 5 or more years.

The researchers defined incident cardiovascular disease as a composite endpoint of coronary heart disease (nonfatal myocardial infarction or fatal coronary heart disease) and stroke (nonfatal or fatal). They calculated person-years of follow-up from the questionnaire return date until date of cardiovascular disease diagnosis, death, or end of follow-up in 2012.

Women with longer duration of antibiotic use were more likely to use other medications and have unfavorable cardiovascular risk profiles, including family history of myocardial infarction and higher body mass index. Antibiotics most often were used to treat respiratory infections. During an average follow-up of 7.6 years, 1,056 participants developed cardiovascular disease.

In a multivariable model that adjusted for demographics, diet, lifestyle, reason for antibiotic use, medications, overweight status, and other factors, long-term antibiotic use – 2 months or more – in late adulthood was associated with significantly increased risk of cardiovascular disease (hazard ratio, 1.32), as was long-term antibiotic use in middle adulthood (HR, 1.28).

Although antibiotic use was self-reported, which could lead to misclassification, the participants were health professionals, which may mitigate this limitation, the authors noted. Whether these findings apply to men and other populations requires further study, they said.

Because of the study’s observational design, the results “cannot show that antibiotics cause heart disease and stroke, only that there is a link between them,” Dr. Qi said. “It’s possible that women who reported more antibiotic use might be sicker in other ways that we were unable to measure, or there may be other factors that could affect the results that we have not been able take account of.”

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

The study was supported by National Institutes of Health grants, the Boston Obesity Nutrition Research Center, and the United States–Israel Binational Science Foundation. One author received support from the Japan Society for the Promotion of Science. The authors had no conflicts of interest.

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SOURCE: Heianza Y et al. Eur Heart J. 2019 Apr 24. doi: 10.1093/eurheartj/ehz231.