To test the association between participant King-Devick Test (KDT) times and obstructive sleep apnea (OSA) severity and evaluate for improvement after continuous positive airway pressure (CPAP) treatment.


Study dates January 30 to July 31, 2018. Patients were referred for initial evaluation of sleep disordered breathing concerns. OSA severities were defined by Apnea Hypopnea Index (AHI) results, with ≥15 considered at least moderate OSA. The KDT is an objective physical measure of brain function. We estimated correlation between KDT time and AHI and compared mean KDT time between patients with and without moderate OSA. For the OSA subgroup, we evaluated for potential improvement in KDT after CPAP.


We enrolled 60 participants, of whom 35 (58.3%) had OSA with an AHI ≥15. Initial analyses noted no significant KDT time differences between patients based on OSA severity. However, after excluding 3 participants who had baseline neurologic illness, adjusted analyses demonstrated that mean KDT time was significantly prolonged for patients with moderate or greater OSA (AHI ≥15) as compared to those with mild or no sleep apnea (AHI <15); 63.4 seconds (95% CI 58.9-67.8) versus 55.7 seconds (95% CI 50.2-61.1), P = .03. CPAP-treated subjects demonstrated significantly improved KDT test times; 63.5 seconds mean pretreatment versus 55.6 posttreatment; −6.6 seconds mean difference, 95%CI (−12.0, −1.13), P = .02.


Neurologic abnormalities in patients with OSA are potentially demonstrable utilizing this objective physical measure. Significant improvement is achieved in patients after CPAP treatment.

Summary Points:

  • Mean K-D test time was significantly longer for patients with moderate or greater obstructive sleep apnea as compared to those with mild or no sleep apnea.
  • CPAP-treated subjects demonstrated significantly improved K-D test times.
  • Using the K-D test aids in providing objective results regarding the subjective improvements many patients report with OSA treatment.
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