Wistar Albino Glaxo Rijswijk (WAG/Rij) rats are widely used in basic and pre-clinical studies as a valid genetic model of absence epilepsy. Spike-wave discharges in these rats appear spontaneously due to disturbance of thalamocortical neuronal circuitry. An abnormal thalamocortical rhythmogenesis in WAG/Rij rats (i.e. dysrhythmia) associates with disturbances of the slow-wave sleep. We examined spike-wave seizures and parameters of sleep using 3-channels electrocorticograms recorded in freely moving rats during approx. 24 h; sleep/waking states and micro-arousals were identified automatically using newly patented approach. We found (1) that more frequent spike-wave seizures in symptomatic rats were linked to a higher degree of NREM sleep fragmentation. (2) Spike-wave epilepsy in our rats seemed to promote micro-arousals during NREM sleep. However, we found peculiar associations between micro-arousals and age-related changes in the incidence of spike-wave seizures. More frequent micro-arousals and a higher number of NREM sleep episodes at the early symptomatic age (5 months) were found in subjects in which spike-wave seizures were reduced between the age of 5 and 7 months. Our results might be interpreted in accordance to the opinion of Peter Halász that micro-arousals – arousals without awaking – might play a «safeguarding function».