Introduction
Sleep disturbances among cancer patients are associated with various psychological morbidities. Among head and neck cancer (HNC) patients sleep disturbances are hypothesized to be highly prevalent. However, there is no precise estimate on the prevalence of sleep disturbance among this population. Our aim is to systematically review the prevalence of sleep disturbances among HNC patients.

Methods
Pubmed, Embase, CINAHL and PsycINFO were searched. Studies reporting the prevalence of any type of sleep disturbance among adults with HNC were included. Study selection, data extraction and quality assessment were performed by two independent reviewers. Meta-analysis of prevalence was performed using random effects model, with I2 values to indicate the extent of heterogeneity. Prevalence rates among different treatment type and phases, measurement instrument used and the quality of included studies were examined.

Results
Twenty-nine studies of accumulatively 2,315 HNC patients were included. The quality was fairly poor and the heterogeneity was high. Studies on three types of sleep disturbances were found: insomnia (17 studies) with pooled prevalence 29% (95% CI 20-41%) before, 45% (95%CI 33-58%) during, and 40% (95%CI 24-58%) after treatment; sleep-related breathing disorders (14 studies) with pooled prevalence 66% (95% CI 44-82%) before and 51% (95% CI 34-67%) after treatment; and hypersomnolence (12 studies) with pooled prevalence 16% (95% CI 7-32%) before and 32% (95% CI 20-48%) after treatment. 

Conclusion
Sleep disturbances are highly prevalent among HNC patients across all phases of treatment. Screening of sleep disturbances and intervention to improve this condition should be initiated soon after cancer diagnosis.

14 - PREVALENCE OF SLEEP DISTURBANCES AMONG HEAD AND NECK CANCER PATIENTS: A SYSTEMATIC REVIEW AND META-ANALYSIS