Purpose: Our previous cross-sectional study showed that periodic limb movements during sleep (PLMS) were frequently found in patients with obstructive sleep apnea (OSA) and that both OSA and PLMS were associated with higher plasma fibrinogen levels. We explored the longitudinal relationships among these factors.
Methods: Plasma fibrinogen levels were measured in 333 consecutive patients who underwent polysomnography to diagnose OSA. Patients who initiated continuous positive airway pressure (CPAP) underwent follow-up polysomnography after 3 months of CPAP use. They were categorized into groups with good or poor adherence (% days with ≥ 4 h/night of CPAP use ≥ 70% or < 70%, respectively). Changes in sleep parameters and plasma fibrinogen levels during the treatment period were compared between these groups.
Results: The cross-sectional analysis of all reviewed 333 patients indicated that fibrinogen levels were associated with the severities of OSA and PLMS. The 60 patients (27 good and 33 poor adherence) who underwent follow-up polysomnography were included in the longitudinal analysis. The median (interquartile range) periodic limb movement index did not change significantly from CPAP titration to the 3-month follow-up (good adherence: 10.5 (0-23.8) to 10.8 (0-70.2) events/h, p = 0.21; poor adherence: 1.2 (0-14.3) to 0.8 (0-15.7) events/h, p = 0.67). However, the plasma fibrinogen level significantly decreased only in the good adherence group (good adherence: baseline 275 ± 46 to follow-up 255 ± 47 mg/dl, p < 0.01; poor adherence: 277 ± 52 to 284 ± 70 mg/dl, p = 0.48).
Conclusions: These results did not support a longitudinal association between PLMS and OSA. However, good adherence to CPAP could reduce plasma fibrinogen levels, thus ameliorating elevations in plasma fibrinogen as a risk factor for future cardiovascular events.
Keywords: Continuous positive airway pressure; Fibrinogen; Obstructive sleep apnea; Periodic limb movements; Treatment adherence.