Causal effects of sleep behaviors on temporomandibular disorders and pain: a bidirectional mendelian randomization study

Background: Temporomandibular disorder (TMD) is a prevalent condition associated with pain and dysfunction of the temporomandibular joint (TMJ) and surrounding structures. Sleep disturbances are common in TMD patients, yet the bidirectional causal relationship between specific sleep behaviors and TMD remains unclear. This study aimed to investigate this relationship using a two-sample Mendelian randomization (MR) approach. Methods: A bidirectional two-sample MR analysis was conducted using genome-wide association study (GWAS) summary statistics for seven sleep behaviors and TMD/TMD related pain (TMD-pain). Single nucleotide polymorphisms (SNPs) were used as instrumental variables. The analysis included data from the UK Biobank and FinnGen Consortium, focusing on individuals of European ancestry. Statistical methods included inverse variance weighting (IVW), MR-Egger regression and sensitivity analyses to ensure robust findings. Results: The analysis identified that genetically predicted “morning person” status reduced the risk of TMD (β: −0.173, p = 0.014), while longer sleep duration decreased the risk of TMD-pain (β: −0.382, p = 0.015). In reverse MR analysis, TMD-pain increased the risk of insomnia, obstructive sleep apnea (OSA) and sleep disorders (p < 0.05). No significant associations were found between other sleep behaviors and TMD or TMD-pain. Conclusions: This study demonstrates a bidirectional relationship between sleep behaviors and TMD. Being a morning person and having longer sleep duration protect against TMD and TMD-pain, respectively, while TMD-pain increases the risk of certain sleep disorders. These findings highlight the importance of addressing sleep issues in TMD management.

GWAS; Temporomandibular disorder; Sleep behaviors; Mendelian randomization

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