Chronic primary insomnia: possible physiopathological involvement of slow wave sleep deficiency

This study was designed to compare the sleep of a carefully selected group of patients with chronic primary insomnia toage- and sex-matched controls, in order to investigate the possible physiopathological role of slow wave sleep deficiency in this disturbance. In addition, the effect of age on normal sleep was studied in a group of 40 normal subjects. Sleep was recorded in the laboratory and automatically scored with an electronic system already described. The general trends of sleep stages were computed. Aging in normal subjects was characterized by a sharp decrease of stage 4, but a good stability of stage 3. Insomniacs' sleep showed a sleep-waking imbalance and a marked deficiency in stages 3 and 4. This deficiency seems to be similar to the age effect in normals, but more accentuated; it cannot be attributed merely to increased pressure of wakefulness. We suggest that slow wave sleep is involved in sleep induction and maintenance, and that its deficiency is linked to the fragility of sleep in chronic primary insomnia.