We further examined expression of apoptosis-related proteins, such as apoptosis-inducing factor (AIF), Caspase 3, B cell lymphoma/lewkmia-2 (Bcl-2) and Bcl-2 Associated X Protein (Bax) and found that chronic OSA increased protein levels of AIF, Caspase 3 and Bax, while decreased protein level of Bcl-2 compared with sham group (P < 0.05, Figure 4B, 4C). Here, CASP3 is linked to obstructive sleep apnea syndrome.