Repeated use of some types of antibiotics may put people at increased risk of developing type-2 diabetes by possibly altering their gut bacteria, according to a large observational study published in the European Journal of Endocrinology. The findings emphasise the need to reduce unnecessary antibiotic prescriptions.
A team from the Departments of Gastroenterology and Medical Oncology at the University of Pennsylvania looked at the number of antibiotic prescriptions given out in the UK to over 200,000 diabetics at least one year before they were diagnosed with the disease, and compared this to the number given to 800,000 non-diabetic patients of the same age and sex.
“Gut bacteria have been suggested to influence the mechanisms behind obesity, insulin resistance and diabetes in both animal and human models,” said lead author of the study, Dr Ben Boursi. “Previous studies have shown that antibiotics can alter the digestive ecosystem.”
Cases were defined as those with incident diagnosis of diabetes. For every case, 4 eligible controls matched on age, sex, practice-site, and duration of follow-up before index-date were selected using incidence-density sampling. Exposure of interest was antibiotic therapy >1 year before index-date. The risk was adjusted for BMI, smoking, last glucose level and number of infections before index-date, as well as past medical history of coronary artery disease and hyperlipidaemia.
They found that exposure to a single antibiotic prescription was not associated with higher adjusted diabetes risk. Treatment with 2-5 antibiotic courses was associated with increase in diabetic risk for penicillin, cephalosporins, macrolides and quinolones with adjusted OR ranging from 1.08 (95%CI 1.05-1.11) for penicillin to 1.15 (95%CI 1.08-1.23) for quinolones. The risk increased with the number of antibiotic courses and reached 1.37 (95%CI 1.19-1.58) for >5 courses of quinolones. There was no association between exposure to anti-virals and anti-fungals and diabetes risk.
This means that patients prescribed 2-5 courses of penicillins increased their risk of diabetes by 8%, while for those with more than five penicillin courses this risk increased by 23%. For quinolones, diabetes risk increased by 15% among patients that were prescribed with 2-5 courses and by 37% for those with more than five courses.
“While our study does not show cause and effect, we think changing levels and diversity of gut bacteria could explain the link between antibiotics and diabetes risk,” said senior author, Dr Yu-Xiao Yang.
There was no increase in risk associated with use of anti-virals or anti-fungal medications and the study found little evidence of a link between antibiotic use and the risk of type-1 diabetes.
“Over-prescription of antibiotics is already a problem around the world as bacteria become increasingly resistant to their effects” said Boursi. “Our findings are important, not only for understanding how diabetes may develop, but as a warning to reduce unnecessary antibiotic treatments that might do more harm than good.”