Weight loss in people with psoriasis is associated with a significantly lower risk of developing psoriatic arthritis (PsA), particularly in the first year after the diagnosis of psoriasis, according to data from two separate real-world cohort studies presented at the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) 2026 Annual Meeting and Trainee Symposium in Lisbon, Portugal. But it was unclear whether taking a GLP-1 receptor agonist had an effect on the risk for PsA that was independent from weight loss.

Both studies involved people diagnosed with psoriasis with no prior PsA or inflammatory arthritis and looked at their risk of developing PsA at 1 year. In one of the studies, even moderate weight loss was found to have a significant impact on overall PsA risk. However, that study could not conclude that GLP-1 users lowered their risk for PsA, whereas the other study that included a larger group of GLP-1 users did reach that conclusion.

Expanding on a Known Association

“Obesity is a well-established driver of psoriatic disease progression. Adipose tissue promotes chronic inflammation through the secretion of pro-inflammatory cytokines and adipokines,” rheumatologist David Kellner, MD, an assistant professor of medicine at the University of California, Los Angeles (UCLA), said at the meeting when presenting the study that had examined the effect of weight loss directly after a psoriasis diagnosis.

Higher body weight is known to increase the risk for PsA in a dose-dependent manner, but what has remained unclear is whether losing weight after a psoriasis diagnosis could reduce that risk, Kellner said.

Few studies have also looked at the association in “a clinically actionable way,” he added, suggesting that the study’s findings could help to inform about the importance of weight loss after being diagnosed with psoriasis.

Impact of Weight Loss Following Psoriasis Diagnosis

Kellner and colleagues’ observational study included 10,721 patients with psoriasis seen at UCLA, of whom 1032 subsequently developed PsA in the first year after receiving their diagnosis. They defined each condition to be present when a patient had ≥ 2 diagnostic codes for it.

Weight loss of ≥ 5% of a person’s total body weight lowered the risk for PsA by 37% (adjusted hazard ratio [aHR], 0.63; 95% CI, 0.41-0.97; P = .03) compared to weight loss of < 5%.

Moreover, the more weight people lost, the lower their risk became, a pattern that held across every weight-loss threshold that was examined. Weight-loss reductions of ≥ 10% or ≥ 15% of body weight vs no weight loss were associated with respective reductions of 49% and 69% in PsA risk.

However, confidence intervals for risk reduction widened with loss of ≥ 10% and ≥ 15% body weight, crossing the line for statistical significance, but this was probably because of the decreasing numbers of patients in the analysis rather than an attenuation of the effect, Kellner said.

“Keeping weight off may matter just as much as losing it,” Kellner said during his oral presentation.

Notably, when any level of weight loss was sustained for up to 2 years, there was an even greater reduction in risk of 68% (aHR, 0.32; 95% CI, 0.12-0.87), although he noted that this was an exploratory finding but “certainly a striking signal” in a real-world population.

GLP-1 Use Lowered PsA Risk

Another presentation at GRAPPA 2026 also suggested a lower risk for PsA among patients with psoriasis treated with GLP-1s.

In a poster presentation of work recently published in the Journal of the American Academy of Dermatology, Alina Feng, a third-year medical student at the University of California, San Francisco, and colleagues analyzed electronic health records from TriNetX, a large US-based claims database.

The investigators evaluated data collected between 2005 and 2025 and used propensity score matching to compare patients with at least two International Classification of Diseases codes for psoriasis who had been treated with a GLP-1 (n = 22,431) and those who had not (n = 23,826). They assessed the subsequent development of PsA or inflammatory arthritis in general over time.

At 1 year, GLP-1 users had a 43% lower risk for PsA than nonusers (HR, 0.57; 95% CI, 0.50-0.64, P < .001). At 10 years, the risk for PsA was 26% lower (HR, 0.74; 95% CI, 0.68-0.80, P < .001) among users than among nonusers. And in a subgroup analysis restricted to the newer GLP-1s, semaglutide and tirzepatide, the 10-year risk for PsA was 36% (HR, 0.64; 95% CI, 0.57-0.71, P < .001) lower among users than among nonusers.

The researchers also reported that the lower risk for PsA among GLP-1 users than among nonusers was observed across multiple other patient subgroups, including those with obesity, type 2 diabetes, and men and women.

The investigators noted several limitations, including the retrospective design, reliance on electronic health record classifications, lack of information on disease severity, and absence of medication adherence data.

Kellner said that his group had also tried to examine whether GLP-1s could account for the weight-loss effect observed in their analysis, but the study was not large enough and did not have long enough follow-up to answer that question definitively.

“Next steps include expansion of our analysis to a [University of California]-wide cohort, which is roughly two and a half times larger, which will hopefully allow us to answer the GLP-1 question,” he concluded.

Neither study had outside funding. Kellner and Feng reported having no financial conflicts of interest. A coauthor of Feng’s study reported receiving research grant funding from Amgen, Janssen, Leo, and Regeneron.

Sara Freeman, MSc, is a freelance medical journalist based in London, England. She has been reporting for specialist healthcare news organizations for more than 20 years.