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