Higher risk of gout in patients with obstructive sleep apnoea

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Patients with obstructive sleep apnoea have a higher risk of developing gout, even beyond the first years after being diagnosed with the sleep disorder, according to UK researchers. They noted that apnoea was associated with a range of serious comorbidities and it had previously been shown that people with it had a higher risk of developing gout in the first year after diagnosis.

To investigate whether they may also be more likely to develop gout over a longer term, the team examined information on 15,879 patients with apnoea and 63,296 without over around six years.

During follow-up, the researchers from UK's Keele University found 4.9% of obstructive sleep apnoea and 2.6% of non-apnoea patients developed gout.

The research paper, “The risk of gout among patients with sleep apnea: a matched cohort study” are published in the American College of Rheumatology’s journal “Arthritis and Rheumatology”

Incidence rates per 1,000 person-years (a person-year represents the number of years of follow-up multiplied by the number of people in the analysis) were 7.83 and 4.03 among those with and without apnoea, respectively, giving a 42% increased risk among apnoea patients.

An elevated risk of developing gout was observed throughout follow-up for obstructive sleep apnoea patients, but it was highest one to two years after diagnosis of obstructive sleep apnoea. This finding was seen in patients with normal body mass index as well as those who were overweight or obese, noted the researchers. However, the risk was greater in those with normal weight.

Study author Dr Edward Roddy said: “People with sleep apnoea are at an increased risk of gout in both the short and long term. Since this risk was highest in people with normal body mass index, doctors and other health professionals should consider the possibility of gout in patents with sleep apnoea regardless of body mass index,” he said.

Both disorders are associated with obesity, high blood pressure, diabetes and other conditions, but after controlling for these and other factors the independent association of apnoea with gout was still evident. The mechanism is unclear, but the researchers noted that it was thought that intermittent oxygen deficiency during sleep encourages the over-production of uric acid, and the accumulation of uric acid crystals in the joints is what causes the inflammation and pain of gout.

Fellow study author Dr Milica Blagojevic-Bucknall said that sleep apnoea is commonly treated with continuous positive airways pressure (CPAP) therapy. "Since CPAP treatment corrects low oxygen levels it might also be expected to reduce uric acid levels, which could possibly reduce the risk of developing gout or treat existing gout. However, further research is needed to investigate the effect of treatment with CPAP in people with gout,” she said.