People with psoriasis who smoke tend to have more severe cases than nonsmokers, but it may be a consequence and not a cause of the skin condition, researchers said on Monday.
The condition, which afflicts up to 3 percent of the world's population and runs in families, varies in severity though heavy smoking was associated with more severe cases, said Italian researchers from Istituto di Ricovero e Cura a Carattere Scientifico in Rome.
"Specifically, patients who smoked more than a pack of cigarettes (more than 20 cigarettes) daily had twice the risk of more severe psoriasis compared with those who smoked 10 cigarettes or less per day," lead author Cristina Fortes wrote in this month's issue of the journal Archives of Dermatology.
The number of years spent smoking also was associated with more severe forms of the condition, which afflicts between 1 percent and 3 percent of the world's population and usually develops between the ages of 15 and 35.
However, an editorial in the journal said the study did not reveal whether smoking was a cause or a consequence of psoriasis, which most often appears in the scalp, knees, elbows and torso and frequently creates embarrassment.
A separate study in the same journal found a higher prevalence of obesity among psoriasis patients. The report by dermatologist Mark Herron of the Utah School of Medicine in Salt Lake City said smoking may have a role in causing psoriasis but obesity was definitely an outgrowth of having the condition.
Psoriasis, which appears to have a genetic component, is caused by an overactive immune system that causes skin cells to develop rapidly and rise to the skin surface where they are not shed rapidly enough and form itchy lesions, according to the National Psoriasis Foundation.
Outbreaks can be triggered by injuries such as scratches or sunburn and severe cases can affect the skin's ability to control body temperature and prevent infections.
