Using antibiotics could increase the risk of diabetes by up to 16 percent, a study showed. Not only the duration but the number of classes of antibiotics affected the risk.

The research team, led by professor Park Sang-min of family medicine at the Seoul National University Hospital, said Monday that it found such outcomes by analyzing data of the National Health Insurance Service to investigate the causal relationship between antibiotics use and diabetes risk.

The research team observed 201,459 adults aged 40 years or older who underwent health screening provided by the NHIS. They collected and analyzed demographic characteristics of the sample population, antibiotic prescriptions, the number of classes of antibiotics used, and diabetes incidence.

The results showed that people with more extended antibiotic use had a higher risk of diabetes. Those who used more classes of antibiotics also had a higher chance of diabetes.

The risk of diabetes was 16 percent higher in people who used antibiotics for 90 or more days than non-users. Those who used five or more classes of antibiotics had a 14 percent higher risk of diabetes than those who used one antibiotic type.

The research team said antibiotics affected the gut microbiota, leading to diabetes in vulnerable populations.

“As this study found the causal relationship between antibiotic use and diabetes in adults aged 40 or more, doctors should prescribe antibiotics carefully after considering benefits and risks,” Park said.

The study was published in the latest issue of Scientific Reports, a sister journal of Nature.