A new observational study published on 25 April in the European Heart Journal suggests there may be a link between the duration and life stage of antibiotic use and cardiovascular events in women. According to the findings, women who take antibiotics for a prolonged period in mid-late adulthood are at increased risk of heart attack or stroke.
The study, led by Prof Lu Qi, director of the Tulane University Obesity Research Centre, Tulane University in New Orleans and adjunct professor of nutrition at Harvard T.C. Chan School of Public Health in Boston, examined 36,429 women as part of the Nurses’ Health Study, a study running in the US since 1976 to investigate risk factors for major chronic diseases in women.
Prolonged antibiotic use increases the risk of cardiovascular events by one-third
The researchers used data from 2004 to June 2012 obtained from women who were 60 years of age or older as of 2004. To compile the information, participants were asked about their previous antibiotic use when they were young (20-39), middle-aged (40-59), or older (60 and older).
The women were then placed into four groups: never used antibiotics; took antibiotics for less than 15 days at a time; 15 days to two months; or two months or longer. Of the 36,500 women, just over 1000 developed cardiovascular disease within the 8-year follow up period.
After adjusting for other factors, such as sex, age, other illnesses, and lifestyle, the researchers predict that women who had used antibiotics for periods of two months or longer in late adulthood were 20–32 per cent more likely to experience cardiovascular events than women who did not use antibiotics.
Qi suggests the increased risk may be caused by an altered gut microenvironment as a result of taking the antibiotics. The loss of “good” bacteria can make room for viruses and bacteria that cause disease.
Furthermore, Qi says, “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”.
Adding that “antibiotics should be used only when they are absolutely needed. Considering the potentially cumulative adverse effects, the shorter time of antibiotic use the better.”
The study only points to a correlation
It’s important to highlight that the nature of the study means that it cannot prove cause and effect, only that there is a link between the two. And as with most observational studies, there are limitations.
The findings were based on participants reporting their own antibiotic use, which could be misremembered. In addition, the researchers were not provided with information on the class of antibiotic used but were simply told about the infection being treated – most commonly, respiratory infections, urinary tract infections, and dental issues.
Finally, the study only assessed middle-aged and elderly women, and therefore, the results cannot be extrapolated to younger women. It is also possible that women taking antibiotics are sicker in other ways that could contribute to their risk of stroke.
Nonetheless, the study is the largest to date to investigated a link between antibiotic use and risk of heart attack and stroke. The results are further strengthened by the long follow up period and the inclusion of additional data pertaining to diet, age, and lifestyle.
(1) Heianza, Y. et al. Duration and life-stage of antibiotic use and risk of cardiovascular events in women. European Heart Journal (2019) DOI: 10.1093/eurheartj/ehz231