["Circadian mechanisms play an important role in the regulation of sleep. A circadian clock-controlled gene, Tef, has been suggested to be associated with depressive symptoms, restless legs syndrome, and slow wave sleep in patients with sleep disorders. The present study sought to explore the association between Tef and sleep disturbances in patients with Parkinson's disease (PD).", 'Three hundred and ninety-two unrelated patients with PD were recruited for this study. All of them completed the PD Sleep Scale (PDSS) and other clinical and demographic assessments. rs738499, a single nucleotide polymorphism of the Tef gene, was genotyped by polymerase chain reaction-restriction fragment length polymorphism.', 'Mean total PDSS scores were 111.5 (standard deviation [SD] 23.0) in the TT genotype and 122.2 (SD 18.2) in the TG+GG genotypes (P<0.01). Significant differences were found between genotypes (TT vs TG+GG) for 14 item scores (all P<0.05). Total and item scores displayed negative associations with the TT genotype (all P<0.05) except Item 2 (P=0.178). Linear regression adjusted for gender, duration, depression and disease severity showed that the polymorphism could explain 0.9% of the variance in PDSS scores.'] Is tef polymorphism associated with sleep disturbances in patients with Parkinson 's disease?