Antibiotics administered to children younger than two years old are associated with several ongoing illnesses or conditions, ranging from allergies to obesity, celiac disease and autism, warn researchers.
For the study, published in the journal Mayo Clinic Proceedings, the research team from Mayo Clinic in the US analysed data from over 14,500 children.
About 70 per cent of the children had received at least one treatment with antibiotics for illness before the age of two years.
The researchers found that babies and toddlers who received at least one dose of antibiotics while under the age of two were more likely to have asthma, autism, allergic rhinitis, weight issues and obesity, food allergies, attention deficit hyperactivity disorder, celiac disease, and atopic dermatitis later in childhood.
Timing and number of doses matters
The findings showed that children receiving multiple antibiotic treatments were more likely to have multiple illnesses or conditions later in childhood.
Types and frequency of illness varied depending on age, type of medication, dose and number of doses. There also were some differences between boys and girls. “Among children who received 1 or 2 prescriptions, only girls were at a significantly higher risk of developing asthma and celiac disease than those unexposed,” wrote study author Nathan LeBrasseur. “Receiving 3 to 4 prescriptions was associated with a higher incidence of asthma, atopic dermatitis, and overweight in both sexes; ADHD and celiac disease in girls; and obesity in boys.
“Both girls and boys who received 5 or more prescriptions had a significantly higher risk of developing asthma, allergic rhinitis, overweight, obesity, and ADHD, and girls also were at a higher risk of celiac disease.”
The age at which babies received the doses also made a difference. Antibiotics prescribed before 6 months of age were significantly associated with the risk of atopic dermatitis, overweight, and ADHD in both sexes; asthma, allergic rhinitis, and obesity in girls; and food allergy in boys.
Differences in antibiotic types
The researchers identified the most commonly prescribed antibiotics (penicillins, cephalosporins, and macrolides) and discovered that there was a difference in their associated risks.
“Exposure to cephalosporins was associated with an increased risk of the highest number of conditions and, uniquely, autism and food allergies,” wrote the research team.
“Penicillins were associated with an increased risk of asthma and overweight in both sexes, celiac disease and ADHD in girls, and obesity in boys, whereas they were associated with a reduced risk of autism in girls.
“Sulfonamides only increased the risk of overweight in boys.
“Macrolides were associated with an increased risk of asthma and overweight in both sexes and allergic rhinitis and obesity in boys, but were associated with a reduced risk of atopic dermatitis in girls and learning disability in boys.”
The researchers believe the difference in results mean that it may be important to differentiate between the type of antibiotics prescribed to young children: “We observed a significantly increased risk of autism and learning disabilities only after exposure to cephalosporins. In fact, cephalosporin exposure was associated with an increased risk of several conditions, suggesting the importance of distinguishing among antibiotics.”
All about the microbiome
The authors speculate that even though antibiotics may only transiently affect the microbiome, this may have long-term health consequences.
The microbiome is the collection of microbes (communities of bacteria, viruses and fungi) in the body that are involved in the development of immunity, defence against pathogens, metabolism function, synthesis of vitamins and fat storage as well as an influence on human behaviour, and it is crucial for the correct function of the human body.
When antibiotics are given it is believed that they attack both the ‘good’ and the ‘bad’ microbes in our bodies, potentially upsetting the balance of the microbiome.
The researchers believe this may be why they found such a significant association between antibiotic prescriptions in the first two years of life and ADHD in both sexes. “The microbiome may affect neural development therefore, practices compromising the establishment of microbial communities may affect the risk of neurobehavioral disorders,” say the research team. “Gut microbiome composition differences have been described for persons with current ADHD, but their significance remains uncertain.”
When antibiotics were first developed and deployed, the overwhelming consideration was control of pathogens. “We now realize that their widespread application has considerable collateral effect on the microbiome, which may be of special importance in developing children.”
While recent data show an increase in some of the childhood conditions involved in the study, experts are not sure why.
Other than the issue of multi-drug resistance, antibiotics have generally been presumed safe by most paediatricians.
However, the researchers are keen to point out that their evidence only points to association between antibiotic use and these health conditions, not causation. “We could not disentangle the effects of antibiotics from those of the underlying conditions, which may have resulted in confounding by indication (eg, antibiotics were prescribed for respiratory infection, which conveyed the risk of subsequent asthma) or reverse causation (eg, respiratory infections are an early manifestation of undiagnosed asthma and may be treated with antibiotics),” said study author Nathan LeBrasseur from the Mayo Clinic.
Nevertheless, antibiotic prescribing patterns in childhood are extremely variable and the researchers noted that the ultimate goal is to provide practical guidelines for physicians on the safest way to use antibiotics early in life: "These findings offer the opportunity to target future research to determine more reliable and safer approaches to timing, dosing and types of antibiotics for children in this age group."
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