From the Journals

Swedish study finds low risk of developing psoriasis in bariatric surgery patients



Obese patients who undergo bariatric surgery have a lower risk of later developing psoriasis, according to results of nonrandomized, longitudinal intervention trial.

Cristina Maglio, MD, of the University of Gothenburg, Sweden, and her associates found that over a 26-year follow-up period, the adjusted hazard ratio (HR) of developing psoriasis was 0.65 (95% confidence interval [CI], 0.47-0.89; P = .008) for patients who underwent bariatric surgery, compared with those who received conventional, nonsurgical obesity treatments. Psoriasis developed in 3.6% of 1,991 patients in the surgery group during follow-up and in 5.1% of 2,018 control patients during follow-up.

Conversely, the difference in the risk of developing psoriatic arthritis (PsA), experienced by up to one-third of patients with psoriasis, was not statistically significant (HR, 0.77; 95% CI, 0.43-1.37; P = .287). PsA developed in 1% of subjects from the surgery group and 1.3% from the control group.

An obese woman sits on a bench ©Vasilis Varsakelis/Fotolia
“In our cohort of patients with obesity and no previous diagnosis of psoriasis or PsA, bariatric surgery was associated with a 32% lower risk of developing psoriasis compared with usual care,” wrote Dr. Maglio and her colleagues. The report is in the journal Obesity.

To understand how surgery affected the development of psoriasis or psoriatic arthritis, the researchers conducted a trial with a control group and surgery group. In the control group, 2,018 patients received standard obesity treatments that included recommendations on eating behavior, food selection, and physical activity. The 1,991 patients in the surgery group underwent gastric banding (375), vertical banded gastroplasty (1,354), or gastric bypass (262). At the start of the study, patients were evaluated for baseline measurements, then again at 6 months. After the 6-month mark, patients were reevaluated at 1, 2, 3, 4, 6, 8, 10, 15, and 20 years, respectively. All study participants, regardless of trial group, were examined and presented patient health questionnaires at each follow-up. The endpoint for this study was the first diagnosis of either psoriasis or PsA. Body mass index decreased significantly in the surgery group, compared with virtually no change in the control group.

Vertical banded gastroplasty was found to significantly lower the incidence of psoriasis, compared with usual treatment. But using gastric banding as a reference, vertical banded gastroplasty (HR, 0.80; 95% CI, 0.46-1.39; P = .418) and gastric bypass (HR, 0.71; 95% CI, 0.29-1.71; P = 0.439) were found to have similar effects on the prevention of psoriasis.

The researchers also identified several risk factors that significantly increased the risk of developing psoriasis. Smoking (HR, 1.75; 95% CI, 1.26-2.42; P = .001), a known risk factor in the development of psoriasis, and the length of time a patient had been obese (HR, 1.28; 95% CI, 1.05-1.55; P = .014) were found to be independently associated with an increased risk of psoriasis.

As part of their risk analysis, Dr. Maglio and her colleagues analyzed the interactions of baseline risk factors such as BMI and obesity duration with the bariatric surgery. This analysis found no significant interactions between baseline risk factors and bariatric surgery. It did reveal that patients who were older at baseline evaluation had slightly better responses to bariatric surgery with lower incidences of psoriasis, compared with younger patients, but the differences were not statistically significant.

“The preventive role of bariatric surgery on the risk of psoriasis has been recently highlighted by a retrospective Danish study (JAMA Surg. 2017 Apr 1;152[4]:344-9),” noted Dr. Maglio and her colleagues. “However, we lent strength to the previous results by confirming this association in a large prospective intervention trial designed to examine the effect of bariatric surgery on obesity-related comorbidities in comparison with usual obesity care.

This study was funded in part by the National Institutes of Diabetes and Digestive and Kidney Diseases, the Swedish Rheumatism association, the Swedish Research Council, the University of Gothenburg, and the Swedish federal government. Dr. Anna Rudin reported that part of her salary at Sahlgrenska University is supported by a grant from AstraZeneca. Dr. Lena M.S. Carlsson has received lecture fees from AstraZeneca, Johnson & Johnson, and Merck Sharp and Dohme. Dr. Maglio and Dr. Markku Peltonen had no relevant financial disclosures.

SOURCE: Maglio et al. Obesity. 2017. Dec; 25[12]:2068-73.

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