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Psoriasis associated with type 2 diabetes, obesity in twin study

Psoriasis had a strong association with type 2 diabetes and obesity in a nationwide study of Danish twins, indicating a common genetic etiology between psoriasis and obesity, according to study results recently published in JAMA Dermatology.

Researchers in Denmark conducted a cross-sectional, population-based twin study that included 34,781 Danish twins born between 1931 and 1982, and aged 20 to 71 years. A questionnaire on psoriasis was validated with psoriasis diagnoses, and compared with diagnoses of type 2 diabetes and self-reported BMI. Data were collected in the spring of 2002 and were analyzed from Jan. 1 to Oct. 31, 2014.

There were 33,588 questionnaire respondents (54% women; mean age, 44.5 years) with complete data included in the study. There was a significant association between psoriasis and type 2 diabetes (OR = 1.53; 95% CI, 1.03-2.27) and between psoriasis and increasing BMI (OR = 1.81; 95% CI, 1.28-2.55) among individuals with a BMI greater than 35.

There were 449 psoriasis-discordant twins included in the study. The association between psoriasis and obesity was diluted in monozygotic twins (OR = 1.43; 95% CI, 0.5-4.07) when compared with dizygotic twins (OR = 2.13; 95% CI, 1.03-4.39).

Using variance component analysis, the researchers found that addictive genetic factors accounted for 68% of the psoriasis susceptibility variance (95% CI, 60-75), 73% of the variance in diabetes susceptibility (95% CI, 58-83), and 74% of the BMI variance (95% CI, 72-76).

Psoriasis and type 2 diabetes had a genetic correlation of 0.13 (95% CI, –0.06 to 0.31), while psoriasis and BMI had a genetic correlation of 0.12 (95% CI, 0.08 to 0.19; P < .001). Environmental correlations were 0.1 (95% CI, –0.71 to 0.17) between psoriasis and type 2 diabetes and –0.05 (95% CI, –0.14 to 0.04) between psoriasis and BMI.

“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,” the researchers concluded. “Results indicate the common genetic etiology of psoriasis and obesity. Conducting future studies on specific genes and epigenetic factors that cause this association is relevant.” – by Bruce Thiel

Disclosure: The researchers report no relevant financial disclosures.