Background: Patients with obstructive sleep apnoea syndrome (OSAS) often display persistent cognitive dysfunction despite effective treatment with continuous positive airway pressure (CPAP). Brain-derived neurotrophic factor (BDNF) is a key mediator of memory and cognition, but its regulation in OSAS and during CPAP treatment is unknown.
Methods: Serum and plasma BDNF concentrations, BDNF secretion by peripheral blood mononuclear cells, and overnight polysomnography were evaluated in 17 men with newly diagnosed OSAS (as defined by a respiratory disturbance index of >10/hour with >70% obstructive events and corresponding daytime symptoms) and 12 healthy control men. In the patients all the parameters were monitored after 1 night and 3 months of CPAP treatment.
Results: There was no significant difference in baseline serum BDNF, plasma BDNF, or spontaneous BDNF secretion by peripheral blood mononuclear cells between untreated patients and controls. After 1 night of CPAP treatment there was a steep fall in median serum BDNF (from 18.0 ng/ml to 4.1 ng/ml) and plasma BDNF (from 58.7 pg/ml to 22.0 pg/ml) concentrations. Following 3 months of treatment BDNF concentrations did not return to baseline. In contrast, BDNF secretion was not suppressed by CPAP treatment.
Conclusions: Patients with untreated OSAS have normal serum and plasma BDNF levels. CPAP treatment is associated with a rapid decrease in serum and plasma BDNF levels which may reflect enhanced neuronal demand for BDNF in this condition.