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Psoriasis Linked To Type 2 Diabetes

May 14, 2016

According to a new study, one more disease is associated with diabetes: twin study suggests genetic link between obesity, psoriasis and diabetes.

The chronic skin condition psoriasis is marked by an inflammation of the skin, resulting in itchy red and pink outbreaks.


The study was done to examine the association among psoriasis, type 2 diabetes mellitus, and body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) in twins.

This cross-sectional, population-based twin study included 34,781 Danish twins, 20 to 71 years of age. Data from a questionnaire on psoriasis was validated against hospital discharge diagnoses of psoriasis and compared with hospital discharge diagnoses of type 2 diabetes mellitus and self-reported BMI. Data were collected in the spring of 2002. Data were analyzed from January 1 to October 31, 2014.

Crude and adjusted odds ratios (ORs) were calculated for psoriasis in relation to type 2 diabetes mellitus, increasing BMI, and obesity in the whole population of twins and in 449 psoriasis-discordant twins. Variance component analysis was used to measure genetic and nongenetic effects on the associations.

The results showed that among the 34,781 questionnaire respondents, 33,588 with complete data were included in the study (15,443 men [46.0%]; 18,145 women [54.0%]; mean [SD] age, 44.5 [7.6] years). After multivariable adjustment, a significant association was found between psoriasis and type 2 diabetes mellitus (odds ratio [OR], 1.53; 95% CI, 1.03-2.27; P = .04) and between psoriasis and increasing BMI (OR, 1.81; 95% CI, 1.28-2.55; P  = .001 in individuals with a BMI>35.0).

Among psoriasis-discordant twin pairs, the association between psoriasis and obesity was diluted in monozygotic twins (OR, 1.43; 95% CI, 0.50-4.07; P = .50) relative to dizygotic twins (OR, 2.13; 95% CI, 1.03-4.39; P  = .04). Variance decomposition showed that additive genetic factors accounted for 68% (95% CI, 60%-75%) of the variance in the susceptibility to psoriasis, for 73% (95% CI, 58%-83%) of the variance in susceptibility to type 2 diabetes mellitus, and for 74% (95% CI, 72%-76%) of the variance in BMI. The genetic correlation between psoriasis and type 2 diabetes mellitus was 0.13 (−0.06 to 0.31; P = .17); between psoriasis and BMI, 0.12 (0.08 to 0.19; P < .001). The environmental correlation between psoriasis and type 2 diabetes mellitus was 0.10 (−0.71 to 0.17; P = .63); between psoriasis and BMI, −0.05 (−0.14 to 0.04; P = .44).

From the results, it was determined that this study determined the contribution of genetic and environmental factors to the interaction between obesity, type 2 diabetes mellitus, and psoriasis. Psoriasis, type 2 diabetes mellitus, and obesity are also strongly associated in adults after taking key confounding factors, such as sex, age, and smoking, into account. Results indicate a common genetic etiology for psoriasis and obesity.

A common genetic link between psoriasis and obesity has been suggested in the past. The condition has also been associated with various risk factors to health, called metabolic syndrome. This new twin study was undertaken in an effort to determine the role genetics plays in connection between the conditions.

Examination revealed 4.1 percent of people without diabetes exhibited psoriasis, compared to 7.6 percent of those with diabetes. People with psoriasis were found to be twice as likely as others to suffer from type 2 diabetes. Average BMIs of people with psoriasis were higher than those without the condition, 25 to 24.4.


Although there appears to be an association between obesity and psoriasis, the cause of the connection is still unknown. It is possible psoriasis could lead subjects to remain sedentary, leading to obesity and diabetes. Another possibility is that these conditions could fuel skin inflammation, resulting in psoriasis. This may be driven by interleukin-6 and tumor necrosis factor in blood, driving both obesity and diabetes.

In addition to a possible genetic link, lifestyle factors, including a sedentary lifestyle, excessive consumption of alcohol, and stress can also lead to these medical conditions.

Practice Pearls:

  • Psoriasis has been shown to be associated with overweight and type 2 diabetes mellitus. The genetic association is unclear.
  • People with severe psoriasis may be at a greater risk for developing type 2 diabetes, according to the results of a new study.
  • The study, published last month in the journal Circulation, also found that people with severe psoriasis may have a higher chance of developing heart disease.

Analysis of the Danish twins study on obesity, type 2 diabetes, and psoriasis was published in the journal JAMA Dermatology.