People who are obese at age 18 may be at an increased risk for psoriatic arthritis later in life, according to a report in the July issue of the Archives of Dermatology.

In a single-center study of 943 psoriasis patients, those who reported being obese at age 18 were three times more likely to develop psoriatic arthritis (PsA), compared with patients who reported having a normal body mass index at age 18, reported Dr. Razieh Soltani-Arabshahi and associates of the University of Utah School of Medicine, Salt Lake City.

In a previous study, the researchers found that patients with psoriasis had an increased BMI, compared with controls. So, they “set out to study if obesity increases the risk of PsA,” using data from a large cohort of subjects enrolled in the Utah Psoriasis Initiative, the researchers noted.

The cohort included consecutive patients older than 18 years who attended university-affiliated psoriasis clinics in 2002-2008 and provided detailed demographic and clinical data. A total of 250 (27%) of the 943 subjects included in the study reported having PsA.

Of the study patients, 14% had been overweight and 5% had been obese at age 18, according to self-reported height and weight measurements.

Higher BMI was associated with an increased risk of developing PsA, independent of other risk factors such as nail involvement. Each unit increase in BMI at age 18 corresponded to a 5% increase in risk of PsA.

In addition, patients who were obese at age 18 showed an earlier onset of PsA, compared with patients of normal weight at age 18. Twenty percent of those who had been overweight or obese at 18 years developed PsA by age 35. In comparison, among patients of normal weight at age 18, 20% did not develop PsA until age 48.

Moreover, patients who had been overweight or obese at age 18 were more likely to report having severe psoriasis (47% and 57%, respectively) than patients who were of normal weight at age 18 (39%).

The design of the study did not permit the investigators to infer causality. However, it is plausible that obesity and its associated inflammatory state might contribute to both psoriasis and PsA, Dr. Soltani-Arabshahi and colleagues reported (Arch. Dermatol. 2010;146:721-6).

“Evaluation of additional sample sets in an attempt to replicate these results is imperative for strong conclusions to be drawn,” they noted.

The study was limited in that it relied on subjects’ self-report of height and weight earlier in life, self-report of psoriasis severity, and self-report of diagnosis of PsA.

The study was supported in part by the Utah Psoriasis Initiative and the Benning Foundation. Dr. Soltani-Arabshahi’s associates reported numerous industry relationships.

07/19/10