Data from a general population study show that patients with sleep apnea may be at increased risk for incident gout, according to researchers from Boston University School of Medicine.
Over the past few decades, the prevalence rate of gout has increased by 3.9% in the United States and 2.5% in the United Kingdom. Gout attacks occur 2.4 times more at night than during the daytime, which could make patients with sleep apnea particularly susceptible to the condition.
Researchers in the United Kingdom analyzed data from The Health Improvement Network to identify 9865 individuals, median age 60 years, with a first-time diagnosis of sleep apnea established between 2000 and 2013. For every patient with sleep apnea identified, researchers matched an additional 5 individuals without sleep apnea to establish up the comparison cohort.
Individuals were matched by sex, age, and year of sleep apnea diagnosis. Because body mass index (BMI) is a major risk factor for both sleep apnea and gout, BMI was also matched within 0.5 kg/m2 to minimize imbalances between the cohorts.
Of the 9865 patients with sleep apnea and the 43,598 comparators, the researchers identified 270 cases of incident gout during a 1-year follow-up period. The rate of incident gout was 8.4 per 1000 person-years for the sleep apnea group and 4.8 per 1000 person-years for the comparator group.
“It is conceivable that sleep apnea may be underdiagnosed,” the authors noted. “Under such circumstances our effect estimates may have been underestimated, because individuals in the comparison cohort (with a mean BMI of 32.2 kg/m2) may have had undiagnosed sleep apnea, thus contributing to the risk of gout.”
The crude rate ratio of incident gout among patients with sleep apnea was 1.7 (95% confidence interval [CI], 1.3-2.2) compared with those without sleep apnea. The rate difference was 3.6 (95% CI, 1.6-5.6) per 1000 person-years. The multivariate rate ratio was 1.5 (95% CI, 1.1-2.1), and the rate difference was 2.8 (95% CI, 0.7-4.9).
The increased risk of incident gout from sleep apnea was present across demographics by age, sex, and obesity status. The authors noted that hypoxia associated with sleep apnea can increase nucleotide production, which generates purines that are metabolized into uric acid. Future studies should evaluate the effects of continuous positive airway pressure on uric acid levels and the risk of gout flares.
“As our findings indicate that these physiologic impacts on uric acid levels can be translated into the risk of gout, and as sleep apnea is particularly common among those with the typical profile of gout patients, effective treatment of sleep apnea-associated hypoxia could add considerably to gout management,” the authors wrote.
The authors note that additional research should examine the potential benefits of correcting sleep apnea-induced hypoxia on the risk of hyperuricemia and gout.