Dziewas et al. noted that sleep apnea is independently associated with raised levels of CRP in acute ischemic stroke patients [11].
In contrast to the subjects in their study, the subjects in the present
study were in the subacute-to-chronic phase of ischemic stroke, suffered from relatively more severe stroke (medium NIHSS 9–11 in
the present study and mean NIHSS 4.3–6.4 in their study), and had
a higher level of CRP (geometric mean CRP 1.50–2.59 in the present
study vs mean CRP 0.37–1.55 in their study). Despite the findings
in the present study that the level of CRP is significantly correlated with AHI and DI in stroke patients with severe OSA, the result
showing the CRP level of the severe OSA group to be significantly
lower than that of the non-severe OSA group argues against the findings of Dziewas et al. [11]. On the contrary, the decreased CRP and
IL-6 level of the severe OSA group corroborate the hypothesis of ischemic preconditioning [28]. The nuclear factor kappa B (NF-κB)
pathway, the primary pathway for the systemic inflammation in patients with OSA, could be activated by reactive oxygen species (ROS)
[37]. Although levels of TAC and CRP were both significantly correlated with OSA severity in the severe OSA group, it is speculated
that the adaptive antioxidative capacity might overwhelmingly outweigh the proinflammatory effect of OSA as the severity of OSA
increased. In contrast, inflammatory status was not mainly
determined by OSA and would not be largely affected by the
antioxidative capacity of the non-severe OSA group.