Antibiotics biomonitored in urine and obesogenic risk in a community-dwelling elderly population

Experimental and epidemiological studies have linked antibiotics use to gut dysbiosis-mediated risk of chronic metabolic diseases. However, whether adiposity is linked to antibiotic exposure in elderly remains inadequately understood.

To investigate the association between internal exposure of antibiotics and adiposity in elderly by using a biomonitoring method.

We included 990 participants (≥60 years) from the baseline survey of the Cohort of Elderly Health and Environment Controllable Factors in Lu'an city, China, from June to September 2016. Forty-five antibiotics and two metabolites in urine were monitored through liquid chromatography-electrospray tandem mass spectrometry (HPLC-MS/MS). Creatinine-corrected urinary concentrations were used to assess antibiotic exposure levels. Body mass index (BMI), waist circumference (WC) and body fat percentage (BFP) were used as indicators of adiposity. Multiple linear regression and binary logistic regression analyses were used to analyze the association of antibiotic concentrations with obesity-related indices. Subsequently, a gender-stratified analysis was performed.

Of the included elderly, 50.7% were defined as having overweight/ obesity, 59.8% as having central preobesity/obesity, and 37.5% as having slightly high/high BFP. Linear regression analysis revealed that a 1-unit increase in the logarithmic transformation of norfloxacin concentrations was related with an increase of 0.29 kg/m² (95% CI: 0.02-0.04), 0.99 cm (95% CI：0.24-1.75), and 0.69% (95% CI：0.21-1.17) in BMI, WC, and BFP, respectively. Compared with the control group, exposure to doxycycline (tertile 2: odds ratio, 2.06 [95% CI: 1.12-3.76]) and norfloxacin (tertile 2: 2.13 [1.05-4.29]; tertile 3: 2.07 [1.03-4.17]) had BMI-based overweight/obesity risk. Additionally, ciprofloxacin (tertile 2: 2.06 [1.12-3.76]), norfloxacin (tertile 3: 2.95 [1.34-6.49]), and florfenicol (tertile 3: 1.84 [1.07-3.14]) were related to WC-based central preobesity/obesity risk. Norfloxacin (tertile 3: 2.54 [1.23-5.24]) was positively associated with a slightly high/high BFP risk. Gender-stratified analysis demonstrated an increased adiposity risk in women compared with men.

Our research provided an evidence that exposure to specific types of antibiotics (tetracyclines and fluoroquinolones) probably from the food chain contributed to obesity in elderly. Prospective cohort studies with larger sample size are warrented to explore the causation.