Sleeping less than 6 hours per night may be associated with more than a 40% higher knee osteoarthritis risk, according to a recent study.

In a large prospective UK Biobank cohort, investigators reported that both habitual short sleep and persistent insomnia were associated with higher risk of incident knee and hip osteoarthritis (OA) after adjustment for occupational factors and body mass index.

Compared with 7 hours of sleep per night, sleeping less than 6 hours was associated with a 41% higher risk of knee OA and 31% higher risk of total knee arthroplasty (TKA). Similar associations were observed for hip OA and total hip arthroplasty (THA). The participants who reported “usually” experiencing difficulty falling asleep or waking during the night had a 34% higher risk of knee OA and a 40% higher risk of TKA compared with those who reported "never or rarely" experiencing sleep disturbance. Night shift work was associated with a 24% higher risk of knee OA and a 28% higher risk of TKA compared with no shift work. These associations were attenuated but remained statistically significant following adjustment for body mass index (BMI). The findings were materially unchanged following the exclusion of participants with chronic knee or hip pain at baseline.

The investigators conducted a prospective cohort study of 502,363 adults aged 40 to 69 years enrolled in the UK Biobank between 2006 and 2010. The participants with prevalent OA, prior TKA or THA, inflammatory arthritis, or autoimmune connective tissue disorders were excluded from the relevant analyses. Sleep duration, sleeplessness or insomnia frequency, chronotype, and shift work characteristics were assessed at baseline using standardized questionnaires. Sleep duration was categorized as less than 6, 6, 7, 8, or more than 8 hours per 24-hour period. Shift work was defined as work outside 9:00 AM to 5:00 PM hours, with night shift work including hours between 12:00 AM and 6:00 AM.

Incident knee and hip OA were identified through linked primary care and hospital records using diagnostic codes, and TKA and THA were identified using procedural codes. Mean follow-up was 8 years for OA diagnoses and 13 years for arthroplasty outcomes. Multivariable Cox proportional hazards models adjusted for age, sex, race, education, Townsend Deprivation Index, frequency of heavy manual work, and occupational walking or standing. Additional models incorporated BMI to assess obesity-independent associations. There were no statistically significant associations between night shift work and hip OA or THA.

Limitations included the reliance on self-reported sleep and occupational exposures assessed at a single time point, the lack of data on duration of exposures, and the absence of radiographic measures or symptom severity data to differentiate structural progression from earlier clinical detection. Residual confounding, including time-varying BMI and occupational demands, couldn't be excluded. In addition, the limited racial and ethnic diversity and potential healthy volunteer bias within the UK Biobank cohort may have affected generalizability.

“As circadian rhythms and sleep can be optimized through lifestyle changes and sleep hygiene interventions, these findings point to new potential ways to prevent OA development and progression,” noted lead study author Elizabeth L. Yanik, PhD ScM, of the Department of Orthopaedic Surgery at the Washington University School of Medicine, and colleagues.

Full disclosures can be found in the study.

Source: Arthritis Care & Research