The performance of critical flicker frequency on determining of neurocognitive function loss in severe obstructive sleep apnea syndrome

: This study aimed to compare the critical flicker frequency (CFF) and the mail-in cognitive function screening instrument (MCFSI) tests' effectiveness in diagnosing neurocognitive function losses in patients having severe obstructive sleep apnea syndrome (OSAS). A total of 85 subjects (47 patients with a diagnosis of severe OSAS and 38 healthy controls) were included into the study. MCFSI scores greater than or equal to five and CFF scores less than 39 Hz were considered abnormal. Demographic and polysomnographic parameters of patients with OSAS were studied, and correlations between the MCFSI, CFF scores and Epworth Sleepiness Scale (ESS) scores were analysed. The mean age of the patients was 49.6 ± 12.0 years. In the OSAS group, the CFF score was found to be low when compared with the control group, while the MCFSI score was found to be high. Pathological CFF scores (<39) were found in 13 patients (27.7%) in the OSAS group, while pathological MCFSI scores (≥5) were found in 19 patients (40.4%). CFF scores were found to be low in only 26% of the patients with OSAS who were found to have high MCFSI scores. MCFSI scores were high in only 38% of the patients with OSAS who were found to have low CFF scores. There was a significant correlation between ESS and CFF scores. In conclusion, the usefulness of the CFF test in determining cognitive function loss in patients with OSAS needs to be demonstrated via studies which utilize a larger sample size.