Sleep characteristics and intervertebral disc degeneration risk: an observational and Mendelian randomization study

Objectives: Sleep disorders are considered a risk factor for aging and skeletal degeneration, but their impact on intervertebral disc degeneration (IDD) remains unclear. The aim of this study was to assess associations between sleep characteristics and IDD, and to identify potential causal relationships.

Methods: Exposure factors included six unhealthy sleep characteristics: insomnia, short sleep duration (< 7 h), long sleep duration (≥ 9 h), evening chronotype, daytime sleepiness, and snoring. The primary outcomes included cervical disc degeneration (CDD) and lumbar disc degeneration (LDD). Firstly, we examined the associations between sleep characteristics and IDD risk in 368,348 participants from the UK Biobank using Cox proportional hazards model. Two-sample Mendelian randomization (MR) analyses were conducted to validate associations found in observational analyses, using genome-wide association data from the UK Biobank and FinnGen consortia.

Results: During a median follow-up time of 13.8 years, a total of 1,637 cases of CDD and 7,654 cases of LDD were identified. Observational analyses found that almost all unhealthy sleep characteristics were associated with an elevated risk of IDD, except snoring. Conversely, the risk of IDD decreased linearly with an increasing number of healthy sleep characteristics. MR analyses supported a causal association between genetically determined insomnia and increased risk of LDD (OR 1.25 [1.07–1.47]), and between short sleep duration and increased risk of both IDD phenotypes (OR 5.41 [1.95–15.01] for CDD; OR 3.48 [1.76–6.89] for LDD). However, long sleep duration was causally associated with a reduced risk of LDD (OR 0.13 [0.03–0.53]), which contrasts with the observational findings.

Conclusion: We found associations between multiple sleep characteristics and IDD risk and confirmed that insomnia and short sleep duration increased IDD risk. Although more research is needed to confirm the underlying mechanisms, prioritizing interventions to improve sleep quality and ensure adequate sleep could help mitigate IDD.