Women who take antibiotics for two months or longer are at increased risk of developing incident kidney stones later in life, suggests a study in American Journal of Kidney Diseases.
The researchers analyzed prospective data on female registered nurses enrolled in the Nurses’ Health Study (NHS) I and II cohorts. Among other medical history items, the women provided information on cumulative time they took antibiotics from age 20 to 39 and from age 40 to 49 (NHS II) or 40 to 59 (NHS I). Incident symptomatic kidney stones were elicited, along with further information about these episodes.
The analysis included 46,336 women from NHS I and 65,988 from NHS II. Associations between antibiotic use and urine composition were analyzed in 5010 participants for whom 24-hour urine collections were available.
Antibiotic use for two months or longer was reported by 4518 women in NHS I and for 7562 women in NHS II. Urinary tract infections were the reason for antibiotic prescriptions in 11% of participants in NHS I and 15% in NHS II.
At both age ranges studied, women using antibiotics for two months or longer were at higher risk of incident kidney stones. Pooled multivariable-adjusted hazard ratios were 2.48 in the 40- to 49/59-year group analysis and 1.36 in the 20- to 39-year group analysis. The association of antibiotic use with kidney stones was similar after exclusion of women reporting urinary tract infection at the time of stone diagnosis or as the reason for antibiotic use. Most urine parameters were similar between groups; participants taking antibiotics for two months or longer had slightly lower values for pH, calcium, and citrate.
Recent studies have suggested that the intestinal microbiome may affect the development of urinary stone disease, possibly by modulating oxalate absorption from the intestine. This raises the possibility that prolonged antibiotic use might increase the risk of stone formation.
The new findings suggest that women who take antibiotics for as little as two months during early adulthood and middle age are at higher subsequent risk of developing kidney stones. “Our data provide an additional reason to minimize the unnecessary use of antibiotics,” the researchers write.
They point out some limitations of their study, including the lack of information on types of antibiotics and the nonstandardized time between antibiotic use and urine sample collection [Ferrar PM, et al. Antibiotic use and risk of incident kidney stones in female nurses. Am J Kidney Dis 2019; 74:736–741].