New research published in the European Heart Journal has found that long-term antibiotic use in women can increase their risk of heart attack or stroke. The research involved 36,429 women from The Nurses’ Health Study.
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The Nurses’ Health Study has been running in the US since 1976. The researchers run some of the most comprehensive investigations into the risk factors associated with chronic disease in women.
The current study used data from 2004 to June 2012 and included women aged 60 or over who were initially free of cardiovascular disease (CVD) at the beginning of the study in 2004.
The aim of the study was to investigate “associations of life-stage and duration of antibiotic exposure during adulthood with subsequent CVD events.”
The women were asked about their use of antibiotics across their life, from ages 20 to 39 (young adulthood), 40 to 59 (middle adulthood), and 60 and over (late adulthood). They were then categorized into four groups: women who had never taken antibiotics, women who had taken antibiotics for periods lasting less than 15 days, women who had taken antibiotics for 15 days to two months, or for two months or longer.
Antibiotics are often “not prescribed appropriately”
The most common reason the women used antibiotics was to treat respiratory infections, urinary tract infections, acne or rosacea, chronic bronchitis, or dental problems, among others.
However, the study states that, according to a separate study, a “substantial proportion of antibiotics are not prescribed appropriately” and that “antibiotic exposure has been found to affect balance and composition of gut microbiota.”
This imbalance of gut microbiota or gut flora (the community of microorganisms found in the digestive tract), can reduce the number of ‘healthy bacteria’ in the gut, increasing the risk of infection from dangerous viruses, bacteria, and microorganisms that can cause illness and disease.
Even a single course of antibiotics can impact long-term health
The study expanded on the effect of antibiotics on gut microbiota:
“Evidence has shown that effects of a single course of antibiotics on the specific microbial populations can persist for years.”
It also hypothesized “Microbiota disruption caused by antibiotics may also lead to weight gain” and increase the risk of thrombosis through “platelet hyperreactivity”, which is also associated with increased CVD risk.
Antibiotic use is the most critical factor in altering the balance of microorganisms in the gut. 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.”
Professor Lu Qi, Tulane University Obesity Research Centre
Antibiotics may increase the risk of cardiovascular disease and stroke
The results of the study showed that over an average of 7.6 years, 1056 of the women included in the study developed cardiovascular disease.
Women who had a history of long-term use of antibiotics (for periods of two months or more) in late adulthood were at a significantly increased risk of developing cardiovascular disease compared to women of the same age who had never used antibiotics.
Adjustments were made to take into account other contributing factors that may influence a woman’s susceptibility to cardiovascular disease and stroke, including age, race, sex, diet, and lifestyle, as well as the reasons for their antibiotic use, obesity level, and whether they were using medication for other conditions or diseases.
It was also discovered that long periods of antibiotic use in middle adulthood was “also related to higher risk of CVD” (cardiovascular disease). However, there was no significant link between antibiotic use in young adulthood and increased risk of cardiovascular disease.
As these women grew older they were more likely to need more antibiotics, and sometimes for longer periods of time, which suggested a cumulative effect may be the reason for the stronger link in older age between antibiotic use and cardiovascular disease.”
Dr. Yoriko Heianza, First Author
It is always important to understand the limitations of scientific studies. Limitations in this particular study include the women in the study self-reporting their antibiotic use, which opens the results up to bias or misremembering., Although, the women were able to give more accurate information on their medication use as they are all health professionals.
Additionally, the researchers did not have specific information on the type of antibiotic used or the doses prescribed. The results also cannot be translated into predictions of CVD risk in younger age groups or in men, as the study focused on CVD risk in women in middle and late adulthood.
On the limitations of the results found by his study, professor Qi explained:
“This is an observational study and so it cannot show that antibiotics cause cardiovascular disease and stroke, only that there is a link between them. 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 to take account of.
Heart attack symptoms in women: Knowing the signs
It is important for women to know the signs of heart attack, as they are often different from the symptoms seen in men, and the symptoms in men are the most widely discussed and recognized in literature due to a multitude of factors.
Symptoms of a heart attack in women include:
- Neck, jaw, shoulder, and upper back or abdominal pain,
- Shortness of breath, pain in one or both arms
- Nausea or vomiting, dizziness
- Unusual fatigue
These symptoms can be subtle and not as obvious as the chest pain we all know to be associated with heart attacks, so often go unnoticed. Women are also prone to underestimate the severity of their symptoms and seek medical help too late.
As heart disease is the most common cause of death in both men and women in the US, more research needs to be carried out in future to definitively solidify the evidence showing that antibiotic use can increase a person’s risk of CVD or stroke.
Yoriko Heianza, Yan Zheng, Wenjie Ma, Eric B Rimm, Christine M Albert, Frank B Hu, Kathryn M Rexrode, JoAnn E Manson, Lu Qi, Duration and life-stage of antibiotic use and risk of cardiovascular events in women, European Heart Journal, , ehz231, doi.org/10.1093/eurheartj/ehz231