Noise-induced hearing loss and obesity: a bidirectional Mendelian randomisation study

BACKGROUND AND AIM: Exposure to environmental noise causes both auditory and non-auditory health effects. Noise-induced hearing loss (NIHL) might play a vital role in the relationship between noise exposure and obesity. While observational studies have demonstrated an association between hearing loss and obesity, the causal nature of these relationships remains unestablished. We aimed to infer the causality between NIHL and obesity-related traits (obesity-RT) from a genetic perspective and gain insight into the noise-obesity relationship. METHODS: We used publicly available genetic summary statistics of genome-wide association studies from four consortia (GIANT, UKBB, FINNGEN, and EGG), including data from European-descent men and women aged 15 and older (number of participants: 36160–681275). Genetic variants used as proxies for NIHL and obesity-RT [BMI, waist-hip-ratio (WHR) and childhood obesity] were derived from the consortia, minimising confounding and sample overlap. We conducted a bidirectional and two sample Mendelian randomisation study to investigate the causal relationships between NIHL and obesity-RT. RESULTS: We found no evidence to support bi-directional causal associations from NIHL to BMI, WHR and childhood obesity [inverse-variance weighted (IVW): 1-unit increase in log odds of NIHL: 0.00 (beta 95% CI: -0.01–0.01), 0.00 (beta 95% CI: 0.00–0.01), 1.00 (OR 95% CI: 0.98–1.01), respectively] and from obesity-RT to the risk of NIHL [IVW: 1-SD increase in BMI: 1.13 (OR 95% CI: 0.78–1.63), 1-SD increase in WHR: 1.19 (OR 95% CI: 0.74–1.92), 1-unit increase in log odds of childhood obesity: 0.93 (OR 95% CI: 0.78–1.10)]. CONCLUSIONS: No clear evidence of a causal effect was seen between NIHL and obesity-RT, in either direction. However, we can still not rule out a modest or non-linear effect of exposures. Future studies may be designed to understand the relationship between them in more detail. NIHL may be a mediator in the noise-obesity relationship. KEYWORDS: noise-induced hearing loss, obesity-related traits, Mendelian randomisation