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Frequent Antibiotic Use Raises the Risk of Type 2 Diabetes

Authors of a new study note that an observed link between antibiotics and diabetes risk may be yet another result of changing levels and diversity of gut bacteria.

Repeated use of some types of antibiotics may increase the risk of developing type 2 diabetes mellitus (T2DM), possibly by altering gut bacteria, according to the results of a large observational study that emphasize the need to reduce unnecessary antibiotic prescriptions.

“Over-prescription of antibiotics is already a problem around the world as bacteria become increasingly resistant to their effects. 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,” said lead author Ben Boursi, MD, a postdoctoral researcher at the Department of Gastroenterology at the University of Pennsylvania, Philadelphia.

The researchers conducted a nested case-control study using a large population-based database from the United Kingdom. They looked at the number of antibiotic prescriptions given to more than 200,000 patients with diabetes at least 1 year before the disease was diagnosed, and compared this with the number given to 800,000 patients without diabetes of the same age and sex.

Key Findings, Analysis   

►► Diabetes risk was increased by up to 37%, depending on the type of antibiotic, number of courses 

►► Penicillin: from 2 to 5 courses increased the risk of diabetes by 8%; >5 courses increased risk by 23%

►► Quinolones: from 2 to 5 courses increased the risk of diabetes by 15%; >5 courses increased risk by 37%

►► No association found between diabetes risk and treatment with imidazole, antiviral drugs, antifungals, regardless of the number of courses

►► Risk was adjusted for BMI, smoking, last glucose level, number of infections before index-date, past medical history of coronary artery disease, hyperlipidemia

►► Analysis repeated in those with no skin or urinary tract infections (common among diabetes patients) with no impact on results

“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 study senior author Dr Yu-Xiao Yang of the University of Pennsylvania.

Dr Boursi added: “Gut bacteria have been suggested to influence the mechanisms behind obesity, insulin resistance and diabetes in both animal and human models. Previous studies have shown that antibiotics can alter the digestive ecosystem.”

Some studies in humans indicate that exposure to antibiotics in early childhood increases the risk of obesity in later in life. Other studies have reported differences in gut microbiota between people with and without diabetes.

The research fits in with studies showing that changes in the composition of gut flora are associated with chronic diseases, including T2DM and cardiovascular and autoimmune diseases.

The researchers published their results online March 24, 2015, in the European Journal of Endocrinology.


Boursi B, Mamtani R, Haynes K, Yang Y-X. The effect of past antibiotic exposure on diabetes risk. Eur J Endocrinol. Published online before print March 24, 2015, doi: 10.1530/EJE-14-1163.