Serum amyloid-beta levels are increased in patients with obstructive sleep apnea syndrome

A critical link between amyloid-beta (A beta) and hypoxia has been demonstrated in in vitro and animal studies but has not yet been proven in humans. Obstructive sleep apnea syndrome (OSAS) is a common disorder that is characterized by nocturnal intermittent hypoxaemia. This study sought to examine the association between the chronic intermittent hypoxia and A beta in OSAS patients. Forty-five cognitively normal OSAS patients and forty-nine age- and gender-matched subjects diagnosed with simple snoring and not OSAS were included in the present study. Serum A beta 40, A beta 42, total tau and phosphorylated tau 181 (P-tau 181) levels were measured using ELISA kits. All subjects were evaluated with nighttime polysomnography and cognitive tests. Compared with the controls, the OSAS patients exhibited significantly higher serum A beta 40, A beta 42 and total A beta levels, and each of these levels was positively correlated with the apnea-hypopnea index, the oxygen desaturation index, and the mean and lowest oxyhaemoglobin saturations in the OSAS patients. Moreover, the OSAS patients exhibited strikingly higher serum P-tau 181 levels, and these levels were positively correlated with serum A beta levels. This study suggests that there is an association between chronic intermittent hypoxia and increased A beta levels, implying that hypoxia may contribute to the pathogenesis of Alzheimer's disease.