CRP evolution pattern in CPAP-treated obstructive sleep apnea patients. Does gender play a role?

C-reactive protein (CRP) is directly implicated in atherogenesis and associated cardiovascular morbidity in patients with obstructive sleep apnea (OSA). Effective continuous positive airway pressure (CPAP) treatment has been shown to gradually decrease CRP levels and thus consequently improve disease-related cardiovascular morbidity. However, the influence of gender on the CRP evolution pattern has never been assessed before. The aim of our study was to investigate possible gender differences in CRP evolution in OSA patients 3 and 6 months after the start of effective CPAP treatment.

The study population consisted of 436 patients (252 males/184 females) with newly diagnosed moderate to severe OSA and good CPAP compliance assessed by a thorough follow up. High-sensitivity C-reactive protein (hs-CRP) was assessed before CPAP initiation and at the third and sixth month of the follow-up period.

C-reactive protein values showed a statistically significant decrease at the third and sixth month of CPAP therapy [initial values 0.79 ± 0.65 mg/dL versus 0.70 ± 0.52 mg/dL (p < 0.05) after 3 months and 0.30 ± 0.33 mg/dL (p < 0.001) after 6 months of CPAP therapy]. When patients were divided into males and females, the above evolution pattern was changed. At the third month time point, the CRP values showed a statistically significant decrease only in males (from 0.74 ± 0.53 mg/dL to 0.61 ± 0.5 mg/dL, p < 0.01) while females showed only minimal and insignificant changes (from 0.87 ± 0.79 mg/dL to 0.83 ± 0.51 mg/dL, p > 0.05). After 6 months' treatment, CRP decreased significantly in both genders (males from 0.74 ± 0.53 mg/dL to 0.28 ± 0.32 mg/dL, p < 0.001 and females from 0.87 ± 0.79 mg/dL to 0.34 ± 0.36 mg/dL, p < 0.001).

Our results suggest a delay in the normalization of CRP levels in females despite effective CPAP treatment. A time period of at least 6 months appeared to be required in women in order to reduce CRP levels and consequent cardiovascular risk. In contrast, CPAP's protective role in males is achieved at an earlier time point. Gender-related hormonal and genetic factors may influence the above CRP evolution pattern.