Dear Editor,

The recent article by Wang et al. was highly interesting and thought provoking [1]. Interestingly, the past few years have seen the identification of novel new biomarkers of obstructive sleep apnea (OSA).

For instance, accentuated levels of the plasma adhesion molecules vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) are seen in patients with OSA. A close positive relationship has been noted between elevated levels of VCAM-1 and the apnea–hypopnea index [2]. A similar relationship exists between ICAM-1 and the oxygen desaturation index. A similar positive relationship exists between VCAM-1 and ICAM-1 and the apnea–hypopnea index.

In addition, E-selectin is elevated in patients with OSA. In fact, E-selectin is an independent indicator of accentuated atherogenesis in patients with OSA [3]. Similarly, higher P-selectin levels are an indicator of more severe OSA. Some studies have shown a similar association between L-selectin and OSA while others have shown no association [2, 4].

Another relatively new marker is plasma thioredoxin. The effectiveness of continuous positive airway pressure (CPAP) in individuals with OSA can be closely monitored by measuring the plasma thioredoxin levels [5]. Hepcidin is another new emerging prognostic marker for obstructive sleep apnea [6]. Similarly, a positive association exists between the apnea–hypopnea index and the morning exhaled 8-isoprostane levels. 8-Isoprostane is reduced following CPAP therapy and serves as an indicator of effectiveness of CPAP therapy [7].

The above examples illustrate the importance of these markers in OSA and the need to increase awareness among physicians about these markers.