MAPT and brain injury: Next, we found that the serum P-tau 181 level was positively correlated with the serum Aβ40 (r = 0.537, p < 0.001), Aβ42 (r = 0.446, p < 0.01) as well as total Aβ (r = 0.511, p < 0.001) levels in the OSAS patients (Fig. 5), suggesting that the OSAS patients with higher Aβ levels may have experienced severe neuronal brain injuries.