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SOS: Surgery reduces gout and hyperuricaemia
The latest paper from the Swedish Obese Subjects (SOS) study group has reported that compared with usual care, bariatric surgery was associated with reduction in gout and hyperuricaemia. Reporting their findings in the Annals of Rheumatic Diseases, the study authors noted that “These results confirm once more that the beneficial effects of bariatric surgery are not limited to weight loss and that they also extend to the prevention of hyperuricaemia and gout.”
The study, ‘Effects of bariatric surgery on gout incidence in the Swedish Obese Subjects study: a non-randomised, prospective, controlled intervention trial’, was designed to assess the long-term effect of bariatric surgery on the incidence of gout and hyperuricaemia in participants of the SOS study.
This latest paper includes 1,982 subjects who underwent bariatric surgery and 1,999 obese controls from the SOS study, a prospective intervention trial designed to assess the effect of bariatric surgery compared with conventional treatment. In the surgery group, 376 subjects underwent gastric banding, 1,369 underwent vertical banded gastroplasty and 265 underwent gastric bypass.
The control group received conventional non-surgical obesity treatment at their centres of registration, ranging from advanced lifestyle modification (including recommendations regarding eating behaviour, food selection, energy intake and physical activity) to no treatment whatsoever. Physical examinations were performed at matching, at baseline and after six months and one, two, three, four, six, eight, ten, 15 and 20 years. At the same time points, questionnaires including a question about current drug consumption were collected. Centralised laboratory examinations, including measurement of serum uric acid levels, were performed at matching, at baseline and after two, ten, 15 and 20 years.
The researchers noted that none of the subjects had gout at baseline. An endpoint on gout incidence was created based on information on gout diagnosis and use of gout medications through national registers and questionnaires. Median follow-up for the incidence of gout was about 19 years for both groups. Moreover, the incidence of hyperuricaemia over up to 20 years was examined in a subgroup of participants having baseline uric acid levels <6.8mg/dL.
The results revealed that bariatric surgery was associated with a reduced incidence of gout compared with usual care (adjusted HR 0.60, 95% CI 0.48 to 0.75, p<0.001). The difference in absolute risk between groups was three percentage points at 15 years, and the number of subjects needed to be treated by bariatric surgery to prevent one incident gout event was 32 (95% CI 22 to 59).
The effect of bariatric surgery on gout incidence was not influenced by baseline risk factors, including body mass index. During follow-up, the surgery group had a lower incidence of hyperuricaemia (adjusted HR 0.47, 95% CI 0.39 to 0.58, p<0.001). The difference in absolute risk between groups was 12 percentage points at 15 years, and the number of participants needed to be treated by bariatric surgery to prevent hyperuricaemia was 8 (95% CI 6 to 13).
Bariatric surgery was associated with a lower incidence of gout during a follow-up of up to 26 years (log-rank p<0.001, unadjusted HR 0.66, 95% CI 0.53 to 0.82, p<0.001; Figure 1). A total of 201 gout events occurred in the control group compared with 138 events in the surgery group.
All three surgical procedures were associated with a lower incidence of gout compared with the control group. Age, creatinine levels, uric acid ≥6.8 mg/dL, hypertension, type 2 diabetes, use of medications associated with gout risk and amount of alcohol intake at baseline were associated with an increased risk of developing gout.
After excluding those who were hyperuricemic at baseline, 314 subjects from the control group developed hyperuricaemia during follow-up compared with 188 from the surgery group (log-rank p<0.001, unadjusted HR 0.51, 95% CI 0.43 to 0.62, p<0.001; Figure 2).
“This matched prospective controlled study shows that bariatric surgery compared with usual care reduces the long-term incidence of gout and hyperuricaemia,” the authors state. “…since hyperuricaemia is the main risk factor for gout development, the decrease in serum uric acid and the prevention of hyperuricaemia are most likely the main factors explaining the association between bariatric surgery and lower risk for gout in obese subjects.”