Gastric bypass tied to lower risk of psoriasis

Last Updated: 2016-12-27

By Marilynn Larkin

NEW YORK (Reuters Health) - Gastric bypass, but not gastric banding, was associated with a significantly reduced risk of psoriasis as well as improved prognosis for those with the condition, researchers in Denmark report.

Dr. Alexander Egeberg of Herlev and Gentofte Hospital in Hellerup told Reuters Health, "In recent years, emerging data has significantly associated psoriasis with obesity, in a disease-severity dependent manner. Moreover, low-energy diets and subsequent weight loss have been reported to improve prognosis of psoriasis."

"The appetite-reducing hormone glucogen-like peptide-1 (GLP-1), which is renowned for lowering glucose, has demonstrated anti-inflammatory abilities, and it has thus been hypothesized that GLP-1 may have anti-psoriatic effects," he said by email.

To investigate, Dr. Egeberg and colleagues analyzed data on all Danish citizens who underwent gastric bypass or gastric banding between 1997 and 2012. Outcomes were new-onset psoriasis or psoriatic arthritis, or progression to severe psoriasis.

Reporting in JAMA Surgery, online December 21, the team identified 12,364 patients who underwent gastric bypass and 1,071 who had gastric banding. Women comprised 76.7% of the gastric bypass group and 74.7% of the gastric banding group.

Rather than using a general population comparison group, the team compared the risk in the same groups before and after surgery. They explained: "This means patients, before surgery, contributed risk time in the presurgery groups and, after surgery, allocated risk time to the postsurgery groups. Consequently, events (diagnosis of psoriasis or psoriatic arthritis) that occurred before the surgery date were allocated to the presurgery groups, and events that occurred after the surgery date were allocated to the postsurgery groups." Presurgery groups were used as the reference groups for all analyses.

The mean age at study start was 27.8 in the gastric bypass subset and 32.3 in the gastric banding subset. Mean age at surgery was 41.0 for bypass and 41.7 for banding.

The gastric bypass group had 158,405 person-years of follow-up before surgery and 33,176 person-years afterward; for gastric banding, there were 9,939 person-years of follow-up before surgery and 6,724 person-years afterward.

Adjusted hazard ratios (aHRs) for new-onset psoriasis were 0.52 for gastric bypass and 1.23 for gastric banding. Similarly, aHRs for progression to severe psoriasis were 0.44 for gastric bypass and 1.18 for gastric banding.

The aHRs for new-onset psoriatic arthritis were 0.29 and 0.53 for bypass and banding, respectively.

Dr. Egeberg said, "We observed a reduced risk and improved prognosis of psoriasis following gastric bypass surgery, whereas no difference was observed for gastric banding. Although differences in post-surgical weight loss may partly explain this observation, our findings could also support the hypothesis of a role for GLP-1. Gastric bypass surgery results in a 20-fold increase in GLP-1, whereas gastric banding does not, likely due to rerouting of ingested nutrients in gastric bypass surgery."

"The findings of our study may therefore help guide clinicians and patients with psoriasis in weight-loss strategies," he concluded.

Dr. Eric Sheu of Brigham and Women's Hospital in Boston, Massachusetts, coauthor of an accompanying editorial, told Reuters Health, "Bariatric surgery reverses many physiologic consequences of obesity - for example, it induces remission of diabetes. This study suggests that bariatric surgery may also reverse immunologic changes seen with obesity and potentially impact a new disease category: disorders of the immune system."

"However, this study only points to a link between bariatric surgery and psoriasis," he said by email. "Future studies will be important to confirm and define the impact of gastric bypass on psoriasis."

"The study raises several interesting questions," he added. These include: "Does sleeve gastrectomy, the most common bariatric procedure in the U.S., also affect psoriasis? Does gastric bypass influence disease course in patients who already have psoriasis? Is the effect of bariatric surgery due to weight loss alone, or are other surgery-induced metabolic, hormonal, or immunologic changes involved? Does bariatric surgery influence the development or prognosis of other disorders of the immune system?"

SOURCE: http://bit.ly/2iAM0OX and http://bit.ly/2hqzQGR

JAMA Surg 2016.