OBJECTIVE: Daily rhythms may be critical for maintaining homeostasis of joint tissues. We aimed to investigate the relationships between circadian clock disruption, sleep, and osteoarthritis (OA) risk in humans.
METHODS: In the UK Biobank, a prospective 500,000-person cohort, we evaluated associations between sleep duration, sleeplessness/insomnia, and shift work type with four endpoints: knee OA, hip OA, total knee arthroplasty (TKA), and total hip arthroplasty. Cox regression was used to estimate associations with OA endpoints adjusting for age, sex, education, race, Townsend Deprivation Index, manual work frequency, and frequency of occupational walking/standing. Associations with and without adjustment for body mass index were estimated, as circadian clock disruption may influence OA through effects on obesity.
RESULTS: For all OA endpoints, risk was highest among those getting <6 hours of nightly sleep (e.g. hazard ratio [HR]s for <6 vs. 7 hours: 1.21-1.41), and 'Usually' experiencing sleeplessness/insomnia compared to 'Never/Rarely' was associated with higher risk (HRs: 1.24-1.40). Night shift workers had 24% higher knee OA risk (HR=1.24 95%CI=1.12-1.38) and 28% higher TKA risk (HR=1.28 95%CI=1.19-1.37) compared to non-shift workers. After controlling for body mass index, associations were attenuated, but short sleep and sleeplessness/insomnia remained associated with all endpoints, and night shift work remained associated with knee OA and TKA. Sleep associations were similar after excluding participants reporting chronic knee/hip pain at sleep assessment.
CONCLUSIONS: Disruption of sleep or circadian rhythms may be modifiable risk factors for OA underlying cartilage degeneration through obesity and obesity-independent pathways. These findings point to potential ways to prevent OA.
