ENO2 and Alzheimer disease: Our observation of altered evening to morning levels of t-tau in blood in response to sleep loss is intriguing in light of our previous findings that demonstrated increased blood levels of neuron-specific enolase and S100 calcium-binding protein B after 1 night of sleep loss, also in healthy young individuals.11 Thus, our findings indicate that even at a young age, sleep loss may alter CNS processes in a direction that promotes neuronal damage and AD pathogenesis.