Taking antibiotics for a long period in early to middle life could increase the risk of developing bowel cancer, researchers say today.
Researchers led by Dr Andrew Chan of Massachusetts General Hospital, Boston, USA, compared antibiotic use against rates of colorectal adenoma, the precursor for most colorectal cancers.
They used figures on antibiotic use at age 20 to 39, and 40 to 59, and colorectal adenoma – measured by colonoscopy – about four years later, among 16,642 women aged 60 years or above. Among the participants there were 1,195 cases of adenoma.
For both of the age categories, increasing duration of antibiotic use was significantly linked to a raised risk of colorectal adenoma.
"Compared with non-users, women who used antibiotics for two or more months between age 20 and 39 had a 36% raised risk," the authors report in Gut today 5 April.
The risk for those who used antibiotics for two or more months between age 40 and 59 was raised by 69%, they calculated. Antibiotic use was linked to low-risk and high-risk adenomas at about the same rate, though the link appeared stronger for proximal than distal adenomas. Furthermore, recent antibiotic use in the past four years was not associated with risk of adenoma, suggesting the effect is not immediate.
Antibiotics fundamentally alter the gut microbiome, explain the authors, by curbing the diversity and number of bacteria, which might have a crucial role the development of bowel cancer.
"The findings, if confirmed by other studies, suggest the potential need to limit the use of antibiotics and sources of inflammation that may drive tumour formation," they conclude.
Cao, Y. et al. Long term use of antibiotics and risk of colorectal adenoma. Gut 5 April 2017; doi 10.1136/gutjnl-2016-313413 [abstract]
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