[Insulin-like growth factor-I and cognitive function in patients with obstructive sleep apnea syndrome]

To explore the possible biochemical mechanism of cognitive impairment in patients with obstructive sleep apnea syndrome (OSAS).

Polysomnography was administered to thirty-six patients with OSAS and eighteen education and BMI-matched controls, all males aged 40 approximately 49 for 8.5 hours at night. Early next morning blood was drawn and serum insulin-like growth factor-I (IGF-I) was determined by immunoradiometric assay. Then neuropsychological tests of visual regeneration, digital symbol, comprehensive memory and digital span were conducted.

The quality of sleep in the patients with OSAS was significantly worse than that of the controls. The score of visual regeneration in the patients with OSAS was 8.4 +/- 2.7, significantly lower than that in control group (11.6 +/- 1.4, P < 0.01). The score of digital symbol in patients with OSAS was 36.92 +/- 8.31, significantly lower than that in the controls (47.8 +/- 6.8, P < 0.01). The serum IGF-I level of the patients with OSAS was: 127.2 +/- 87.0 ng/ml, significantly lower than that of the controls (194.03 ng/ml +/- 77.31 ng/ml, P < 0.05). The IGF-I level was significantly positively correlated with the scores of visual regeneration test (r = 0.381, P < 0.05) and digital symbol test (r = 0.330, P < 0.05), lowest SaO(2) (r = 0.371, P < 0.05), mean SaO(2) (r = 0.333, P < 0.05) and REM sleep duration (r = 0.598, P < 0.01).

Decrease of serum IGF-I level may play a role in the cognitive impairment in patients with OSAS. Nocturnal hypoxemia and REM sleep deprivation may be the reason of the decrease of the serum IGF-I level in patients with OSAS.