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

## TL;DR

This study finds that sleep behaviors like being a morning person or sleeping longer can reduce the risk of temporomandibular disorders and pain, while TMD-related pain can also increase sleep problems.

## Contribution

The study is the first to use bidirectional Mendelian randomization to establish a causal link between sleep behaviors and TMD/TMD-pain.

## Key findings

- Genetically predicted 'morning person' status reduces the risk of TMD.
- Longer sleep duration decreases the risk of TMD-related pain.
- TMD-pain increases the risk of insomnia and sleep disorders.

## Abstract

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.