Psoriasis associated with diabetes, BMI and obesity

by Bruce Sylvester: Psoriasis appears to be associated with type 2 diabetes, body mass index and obesity, researchers from a twin study reported on April 27, 2016 in JAMA Dermatology.

“Psoriasis, type 2 diabetes mellitus and obesity are strongly associated in adults after taking key confounding factors such as sex, age and smoking into account. Results indicate a common genetic etiology of psoriasis and obesity. Conducting future studies on specific genes and epigenetic factors that cause this association is relevant,” said lead investigator Ann Sophie Lønnberg, M.D., of the University of Copenhagen, Denmark, and her coauthors.

As background, the authors noted that psoriasis has previously been associated with the metabolic syndrome, particularly with obesity and diabetes. Twin studies are used to explicate shared causes of associated diseases.

The investigators evaluated data on 33,588 twins, aged 20 to 71. They found that 4.2 percent had psoriasis, 1.4 percent had type 2 diabetes and 6.3 percent were obese.

Among the nearly 459 subjects with type 2 diabetes, about 7.6 percent also had psoriasis. Among subjects without type 2 diabetes, just 4.1 percent had psoriasis.

Notably, subjects with psoriasis tended to be heavier than those without psoriasis.

Risk for obesity was also greater among those with psoriasis; 11 percent of those with psoriasis were obese, and 8 percent of non-obese subjects had psoriasis.

The researchers found 720 twin pairs discordant for psoriasis, i.e. one twin had the disease and the other did not. Twins with psoriasis had a higher BMI than the co-twins without psoriasis, and they were more likely to be obese.

Prevalence of diabetes was the same in twins with psoriasis compared with the co-twins without psoriasis.

In an accompanying editorial, Joel M. Gelfand, M.D, of the University of Pennsylvania Perelman School of Medicine, Philadelphia, “The unique twin design of the study by Lónnberg and colleagues, in which increasing BMI was associated with a diagnosis of psoriasis, allowed the investigators to identify a genetic correlation between psoriasis and BMI.”