Antibiotics normally don’t increase the risk of autoimmune disorders

Children exposed to antibiotics in the uterus or at the start of life generally do not have an increased risk of developing autoimmune conditions in adolescence, according to a study of more than 6 million children. But the relationship is complicated.

The idea that antibiotics could contribute to autoimmunity date back to the 1980s, when David Strachan, then to the London School in hygiene and tropical medicine, suggested that fewer infections and cleaner environments can explain the increases in infant allergies.

This has led to the development of the hygiene hypothesis. This proposes that an early exposure to certain microbes leads to the immune system, preventing it from excessively reacting to harmless substances and causing allergic reactions or autoimmune conditions. These conditions, such as type 1 diabetes, inflammatory intestine disease and lupus, occur when immune cells inadvertently attack the body’s own tissues.

Since then, many studies have shown that many microbes – especially those of our intestines – shape our immune system. For example, some produce essential compounds for the development of specialized immune cells, called regulatory T cells, which help prevent autoimmunity. This has led to questions about the question of whether antibiotics, which considerably modify the intestinal microbiome, can contribute to the development of autoimmune conditions.

“Over the years, there has been a lot of preclinical work carried out, mainly in animal models, which strongly supports this notion that antibiotics, or the modulation of the intestinal microbiome, have a major impact on our immunity,” explains Martin Kriegel at the University of Münster in Germany.

For example, a 2016 study in mice showed that the repeated use of antibiotics early in life increases the risk of diabetes type 1.. Mice genetically sensitive to the disease have been exposed to an antibiotic three times – once through their mother’s breast milk and again at 4 and 5 weeks. About 50% of male mice and 80% of the female mice in this group developed type 1 diabetes at the age of 30 weeks. In comparison, only about 25% of male mice and 50% of female mice which were not exposed to antibiotics developed the condition.

Human studies have also referred to a link. An analysis of more than 10 million people published earlier this year revealed that those who prescribed an antibiotic presented a risk of 40% higher, on average, to be diagnosed later with an inflammatory intestine disease. Meanwhile, a 2019 study of more than 110,000 people found that antibiotic prescriptions were associated with a 60% higher chance of developing rheumatoid arthritis.

But other research has shown the opposite. For example, a 2017 study of more than 15,000 children tested type 1 diabetes or celiac disease found no association between the development of these conditions and the use of antibiotics before the age of 4.

More recently, Eun -Young Choi at Sungkyunkwan University in South Korea and his colleagues followed the impact of six autoimmune conditions – type 1 diabetes, chronic childhood arthritis, ulcerative colitis, Crohn’s disease, lupus and Hashimoto’s disease – in addition to 2.6 million children whose mothers had an infection during pregnancy. About 1.5 million of their mothers were prescribed antibiotics during pregnancy. The researchers then did the same in a group separate 3.4 million children who had an infection within six months of birth, of which 1.9 million were treated with an antibiotic.

After taking into account factors such as type of infection, socioeconomic status and sex, researchers found no global association between children’s exposure to utero antibiotics or early childhood and a later risk of developing an autoimmune condition in adolescence.

So why is there so much divergence between studies? The problem is that the intestinal microbiome is extremely complex. A wide variety of factors influence, which makes almost impossible for researchers to account for them all. For example, none of the studies mentioned above adjusted for the diet, which can considerably modify the intestinal microbiota.

Different antibiotics can also have different effects. For example, Choi and his team found an association between the use of broad spectrum antibiotics during pregnancy and children later developing Crohn’s disease. The age of the exhibitors in the exhibition also seemed to have of importance. Antibiotics prescribed within two months of birth presented a 30% risk of Hashimoto’s disease.

This does not mean that we should give up antibiotics. “When the use of antibiotics during pregnancy is recommended, it is because the evidence suggests that the advantages prevail over possible risks”, Christopher Zahn at the American College of Obstetricians and Gynecologists in Washington DC. For example, urinary tract infections increase the risk of premature birth, low birth weight and serious complications, such as sepsis, he says.

Some antibiotics can even protect themselves from autoimmunity. A 2018 study revealed that pathogenic bacteria infection Enterococcus Gallinarum The autoimmunity triggered in mice predisposed such conditions. Treating them with antibiotics not only prevented them from dying, but also prevented their immune cells from attacking their body.

“So everything is terribly complex,” says Kriegel.

However, the most recent results should be reassured of antibiotics to those who are pregnant or who have young children, explains Zahn.