We found that in the presence of TNF-α or CRP, two inflammatory markers known to be increased in severe OSA patients, the CCR2 mRNA expression could be further enhanced at least 75% by intermittent hypoxia, suggesting the intermittent hypoxia-induced CCR2 mRNA expression in monocytes could further be up-regulated in the presence of other factors involved in severe OSA. Here, CCR2 is linked to obstructive sleep apnea syndrome.