Use of computerized visual performance test in assessing day-time vigilance in patients with sleep apneas and restless sleep.

We have studied day-time vigilance in 31 patients (median age 49 years) with suspected sleep disorders using a new visual reaction time and performance test. The findings in the day-time vigilance test were compared with the number of desaturation events and movement arousals measured with a sensitive movement detector in the night-time. In our statistical model the high number of desaturations correlated with a high dispersion in reaction-times. The squared multiple r was 0.465 in a model where the dispersion of reaction times was the dependent variable and the number of desaturations, duration of quiet sleep and the mode of oxygen saturation were independent variables. A high amount of body movements (movement arousals, duration less than 5 seconds) correlated with gradual deterioration in the performance test. The squared multiple r was 0.447 in a model where the regression coefficient of reaction times was the dependent variable and active sleep and number of body movements less than 5 seconds in duration were the independent variables. Frequent arousals in apnoeic patients are observed in hyper-excitable responders and are known to cause sleep deprivation and hypersomnia. Our findings in desaturating patients indicate that in those with a low chemoreceptor response to hypoxia the failure in day-time regulation of vigilance may differ from the failure associated with sleep-deprivation.