According to researchers at Norwegian University of Science and Technology (NTNU), higher weight is a contributing factor to developing psoriasis. However, doctors at the Department of Dermatology at St. Olavs Hospital remain uncertain about just how higher weight can lead to psoriasis.
“We still don’t know enough about the mechanisms behind this connection. Fatty tissue is an organ that produces hormones and inflammatory signalling molecules, which could be a contributing factor,” Dr. Mari Løset said in a press release.
“Higher BMI [Body Mass Index] may contribute to increased inflammation of the skin, which can exacerbate psoriasis, but it could also be that psoriasis leads to a person being less physically active and thus gaining weight.”
In an observational study including researchers from NTNU, England and North America, the Mendelian randomization method was used to observe 750,000 individuals. The method is named after Gregor Mendel, considered the father of genetics.
According to Mendel's principles of inheritance, whether the offspring inherits a certain variant of genes from the mother or father is random. Genetic variants are randomly distributed, or randomized, between individuals.
“Mendelian randomization means that nature itself distributes individuals randomly into groups based on genes. This way, we can avoid the results being influenced by external factors,” Løset explained.
“Our understanding of how genes are related to disease is increasing at record speed, and in this study, we used known genetic variants as markers for BMI and psoriasis.”
Using Mendelian randomization, the researchers found that higher weight is a contributing factor to psoriasis. They observed that greater BMI increased the chance of developing the disease.
“We calculated that the risk increased by nine per cent for each higher whole number on the BMI scale,” Løset says.
But the researchers are still uncertain about just how higher weight can lead to psoriasis.
Worldwide, 2 to 4% of the population is affected by psoriasis. The incidence is particularly high in Norway.
“Psoriasis is a very complex disease and we hope to study subgroups, especially individuals with severe psoriasis. The hypothesis is that we will be able to observe even greater links with higher weight,” said Løset.