The spontaneous eye-blink as sleepiness indicator in patients with obstructive sleep apnoea syndrome-a pilot study

To evaluate the spontaneous eye-blink as drowsiness/sleepiness indicator in patients with obstructive sleep apnoea (OSA) syndrome.

Using a contact-free sensor for the recording of spontaneous eye-blinks, we investigated the diagnostic value of spontaneous blink parameters in 21 OSA patients. Before the study, all patients underwent a night of polysomnography. Eye-blinks were studied the following morning before therapy, and again after the first therapy night with nasal continuous positive airway pressure (nCPAP), to investigate whether blink parameters reflected changes of alertness pre- and post-nCPAP treatment. General daytime sleepiness was assessed using the Epworth Sleepiness Scale (ESS). The current subjective state was determined by means of standardised questionnaires directly before recording the eye-blinks. Studies were conducted in two sleep laboratories in hospitals.

In OSA patients with excessive daytime sleepiness (EDS; ESS >10, respiratory disturbance index [RDI]=42.4) several parameters proved informative for sleepiness diagnostics. Reduction of blink duration and reopening time as well as increase in blink frequency were significant; furthermore, proportion of long-closure duration blinks indicated reduced sleepiness. OSA patients without EDS (ESS < or =10, RDI=33.5) did not reveal systematic changes of the blink parameters registered after one night of nCPAP intervention.

Specific parameters of the spontaneous eye-blink may be applied as a sleepiness index for diagnostics in OSA patients. Further studies are needed to prove the diagnostic value of blink parameters and their advantages in comparison to subjective measures commonly used in clinical studies.