What can blood biomarkers tell us about cardiovascular risk in obstructive sleep apnea?

Despite its high prevalence and frequent association with multiple comorbidities, including hypertension, heart disease, and stroke, obstructive sleep apnea (OSA) still lacks appropriate tools for cardiovascular risk assessment and stratification. Circulating biomarkers represent a safe, convenient, and inexpensive possibility, and several studies have been performed to define an ideal marker in this context. Additionally, biomarkers can provide insight into the pathological mechanisms of the disease and suggest new therapeutic approaches. In the present review, the authors critically analyze the biomarkers of cardiovascular risk currently available and other potential markers, including brain natriuretic peptide, C-reactive protein, tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), cysteine, homocysteine, free fatty acids, 8-isoprostane, gamma-glutamyl transferase, glycated hemoglobin, adipokines, and adhesion molecules. The results clearly demonstrate that the relationship between specific biomarkers and OSA is often influenced by age, gender or ethnicity, which has hindered the identification of a unique marker for the evaluation of all patients with OSA. Moreover, given the frequency of comorbidities in OSA, which, by themselves, increase the cardiovascular risk, all confounding factors must be considered in the evaluation of these biomarkers.