Women who took antibiotics for two months or more between the ages of 20 and 59 had higher risk of colorectal adenoma, a recent study found.
Researchers used data from the Nurses' Health Study to evaluate the association between colorectal adenomas and antibiotic use at ages 20 to 39 years, at ages 40 to 59 years, or within the past four years. The study included 16,642 women age 60 years or older who underwent at least one colonoscopy. Results were published online by Gut on April 4.
The study found 1,195 cases of adenoma and a significant association between adenomas and increased duration of antibiotic use between ages 20 to 39 years and ages 40 to 59 years. Compared to those who didn't take antibiotics between 20 and 39 years, women who took them for two months or more in that age range had a multivariable odds ratio (OR) for adenoma of 1.36 (95% CI, 1.03 to 1.79). The OR for an adenoma with antibiotic use between ages 40 and 59 years was 1.69 (95% CI, 1.24 to 2.31). Antibiotic use within the past four years was not associated with risk of adenoma. The associations were similar for low-risk and high-risk adenomas, but there appeared to be a modestly stronger association with proximal adenomas compared to distal ones. The study authors noted that proximal adenomas are less likely to be detected on screening colonoscopy.
The authors concluded that long-term antibiotic use in early to middle adulthood was associated with risk of colorectal adenoma and said they believe this study is the first to identify this dose-dependent link. Previous research has found associations between antibiotic use and development of colorectal cancer, which would support the current study's findings. Such associations are also biologically plausible, given how antibiotics affect gut microbiota, the authors said. It is also possible that the pathogens that necessitated the use of antibiotics could have induced inflammation, a known risk factor for colorectal cancer.
Strengths of the study include that it was controlled for a range of potentially important confounders and that the reports of participants in the Nurses' Health Study are likely to reflect actual antibiotic use. Limitations include that information wasn't gathered on spectrum or route of administration, so no conclusions can be drawn about effects of different antibiotic classes, and that the specific timing of antibiotic exposure relative to development of adenoma couldn't be determined.