Obstructive sleep apnoea in obese women
Published Date: 19th July 2016
Publication Authors: Hardy KJ
Background
Recent studies have highlighted an association between gout and obstructive sleep apnoea (OSA), reflecting shared risk factors with increasing body weight associated with gout and OSA. However, intermittent episodes of hypoxia in OSA may lead to purine breakdown and increase uric acid levels, potentially contributing to hyperuricaemia. This study aimed to investigate serum urate levels in an obese cohort with and without OSA.
Methods
A cohort of patients with obesity (BMI >30 kg/m2) attending weight management clinics were identified. No patients were taking urate lowering therapies or reported a prior history of gout; all were continuous positive airway pressure (CPAP) naive. Serum urate was measured and patients had overnight polysomnography. OSA was defined as apnoea-hypopnoea index (AHI) >5. A binomial variable was created for high urate with the cut-off at the median urate. Multivariate logistic regression was used to identify association between high urate and OSA adjusting for age, smoking status, hsCRP and BMI.
Results
92 patients (46 male, 46 female) were recruited. Mean age 48.5 (S.D.9.4) years. Median BMI [males 36.6 (IQR 33.1, 42.4) (kg/m2); females 43.8 (IQR 38.8, 46.7) kg/m2]. Median urate 346 [IQR 288, 413] (mmol/l). OSA was diagnosed in 31 (67%) females, 30 (65%) males. Increased urate was associated with OSA in univariate analysis [OR 2.4 (95% CI 1.0, 5.9)]. Gender stratification revealed no significant association between OSA and higher urate in males [OR 1.65 (0.45, 6.03)] but a strong relationship between OSA and higher urate in females [OR 10.1 (1.1, 86.9)]. This remained significant in the female subgroup after adjusting for smoking, hsCRP, BMI, age [ORadj 10.2 (1.1, 93.5)].
Conclusion
This small study has demonstrated that in female obese patients, OSA is associated with an 8 fold increased odds of having an increased urate even after adjusting for obesity, smoking, inflammation and age. Recurrent nocturnal hypoxia may contribute to increased urate production. No significant association was observed in male obese patients. Female patients with OSA may be a greater risk of gout. Prospective studies are necessary to discover if treatment of OSA with CPAP to correct hypoxia lowers urate levels.
Seetho, IW; Hardy, KJ et al. (2014). Urate is associated with obstructive sleep apnoea in obese women . Rheumatology. 53 (Suppl 1), i163
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