Abstract
Although previous epidemiological studies have investigated the correlation between hypothyroidism and obstructive sleep apnea (OSA), the results are controversial and conflicting. Therefore, we used a bidirectional 2-sample Mendelian randomization (MR) approach to infer the causal relationship between hypothyroidism and OSA. We performed a bidirectional 2-sample MR analysis to infer the causal relationship between hypothyroidism and OSA using genome-wide association study (GWAS) data. The hypothyroidism dataset was obtained from GWAS of the IEU database (https://gwas.mrcieu.ac.uk/). The GWAS dataset associated with OSA was obtained from the FinnGen Biobank (https://www.finngen.fi/en). MR results were estimated using the inverse variance weighted, weighted median, MR-Egger, simple mode, and weighted mode methods. Sensitivity analysis was conducted using the heterogeneity, pleiotropy, and leave-one-out tests. Scatter plots, forest plots, funnel plots, and leave-one-out plots were used as visualizations of MR results. According to the inverse variance weighted method, forward MR analysis showed that hypothyroidism was significantly associated with OSA (odds ratio, 1.870 [95% confidence interval, 1.055-3.315]; P = .032). There was no evidence to suggest a causal relationship between OSA and the risk of hypothyroidism in reverse MR analysis (P = .881). Furthermore, sensitivity analysis further confirmed the robust results. Our bidirectional 2-sample MR analysis revealed that hypothyroidism could increase the risk of developing OSA but did not provide evidence to support a causal relationship of OSA on hypothyroidism. Thus, patients with hypothyroidism should strengthen their sleep quality monitoring, and further research is needed to understand the role of hypothyroidism effects on OSA.