C-reactive protein improves the ability to detect hypertension and insulin resistance in mild-to-moderate obstructive sleep apnea: Age effect.

C-reactive protein (CRP) appears to improve the ability to detect cardiometabolic risk in young and middle-aged adults with mild-to-moderate obstructive sleep apnea (mmOSA). The aim of this study is to assess utility of CRP in identifying the risk of hypertension and insulin resistance across a wide age range including older patients with mmOSA. Adults (n = 216) of a wide age range (28-90 years old, mean age 52.64 ± 12.74) with mmOSA (5 ≤ AHI < 30) completed in-lab polysomnography or home sleep apnea testing, physical examination including blood pressure (BP) measures, structured medical history questionnaire, and blood draw for CRP and fasting glucose and insulin levels. In adults < 60 years, lnCRP but not the apnea-hypopnea index (AHI) was associated with greater odds for hypertension (odds ratio [OR] = 2.40, 95% CI = 1.20-4.84, p = 0.01; OR = 1.00, 95% CI = 0.92-1.08, p = 0.92, respectively) and with higher average systolic and diastolic BP. Also, in adults < 60 years lnCRP but not AHI, was associated with higher lnHOMA values. In contrast, in adults > 60 years neither lnCRP nor AHI were associated with greater odds for hypertension, average systolic and diastolic BP, and lnHOMA. Receiver-operating characteristics curves revealed that adding CRP to standard clinical factors (age, sex, and BMI) yielded moderately good risk models for hypertension in patients < 60 years (AUC = 0.721). In conclusion, CRP improves the ability to detect cardiometabolic risk in young and middle-aged, but not older adults with mmOSA, suggesting that inflammation may be a primary pathogenetic mechanism in younger patients with OSA.