Hyperuricemia: A predictor of severe obstructive sleep apnea in a Tunisian population with atrial fibrillation?

Background Obstructive sleep apnea (OSA) is involved in initiation of atrial fibrillation (AF). Uric acid has emerged as an independent marker of morbidity and mortality in several cardiovascular pathologies. But there are few data addressing the association of uric acid levels and OSA in AF patients. Aim The purpose of this study was to investigate whether the levels of serum uric acid were correlated with OSA severity in Tunisian patients with AF. Methods It was a study which included 100 patients followed for non-valvular AF. Non-inclusion criteria were: gout and/or treatment with allopurinol, chronic lung disease with hypoxemia and severe chronic kidney disease. All patients underwent overnight polygraphy. Fasting blood samples were obtained to dose serum uric acid. Results OSA's diagnosis was retained in 90% of patients: mild in 32% of cases, moderate in 27% of cases and severe in 31% of cases. The mean value of serum uric acid was 61.05 ± 19.4 mg/L. Hyperuricemia was found in 31 patients. Forty-eight percent of patients diagnosed as having hyperuricemia, had also severe OSA. We did not find significant correlation between OSA's diagnosis and uric acid levels. But we note a significant correlation between the level of uric acid and the AHI (P = 0.02) and there was a statistically significant association between hyperuricemia and severe OSA (P = 0.04). According to the ROC curve for predicting severe OSA, the cut-off value of serum uric acid was about 56.5 mg/L (with a sensitivity of 61.5% and specificity of 57%). Conclusion In our study conducted in a Tunisian population with AF, we did not find a significant difference in uric acid levels between patients with OSA and those without OSA. But we have demonstrated a significant correlation between the increased levels of serum uric acid and severe OSA. So, it seems to be interesting to propose a routine screening of OSA, in patients having AF and hyperuricemia, whose main goal is to detect severe forms of OSA.