Abstract
Melatonin is a sleep-inducing hormone that is secreted from the pineal gland. Although it is used to treat sleep disorders in patients with severe motor and intellectual disabilities (SMID), no studies to date have examined melatonin secretion in patients with SMID. We measured salivary melatonin concentration at noon and midnight in 13 patients with SMID living at our institution (all subjects were tube fed and had underwent a tracheotomy and 9 subjects used an artificial ventilator) and compared measurements to 5 healthy controls. Only one SMID subject had an abnormally low nocturnal melatonin concentration, while 7 had abnormally high concentrations. Twelve had abnormally high diurnal melatonin concentrations, indicating that most subjects did not have impaired melatonin secretion, but rather higher concentrations than normal. The ratio of diurnal to nocturnal concentration was 0.64 ± 0.43 in SMID subjects, which was significantly higher than healthy controls (0.18 ± 0.06; p = 0.02). As high diurnal to nocturnal concentration was significantly correlated with conditions such as lack of visual tracking and a dilated third ventricle, the high ratio in SMID subjects may indicate impairment of the melatonin secretion suppression system from the retina to the pineal gland. Presence of daily epileptic seizures was also significantly correlated with high diurnal to nocturnal melatonin concentration.
