THURSDAY, Dec. 22, 2005 (HealthDay News) -- People with psoriasis are more likely to be smokers, and the smoking habit appears to make the skin condition worse, according to two new studies.
The finding "highlights the importance of smoking cessation in patients with psoriasis," according to the Italian team that led one of the studies.
The second report found that people with psoriasis are also more likely to be obese than people without the skin ailment.
Both studies appear in the December issue of the Archives of Dermatology.
In the first report, a team led by Cristina Fortes, from the Istituto di Ricovero e Cura a Carattere Scientifico, in Rome, collected data on 818 patients who had psoriasis.
The researchers found that patients who smoked more than a pack of cigarettes a day had twice the risk of having more severe psoriasis, compared with patients who smoked 10 cigarettes or less a day. They also found that psoriasis was more severe among women who smoked than men who smoked.
In the second report, researchers found that people with psoriasis were more likely to smoke and also more likely to be obese. However, patients tended to start smoking and gain weight after they developed the condition, the researchers reported.
"Psoriasis is a disease that does something to the psyche that causes patients to care less about their appearance. Because they care less about their appearance, they are more willing to partake in other risky behaviors," speculated lead researcher Dr. Gerald G. Krueger, a professor of dermatology at the University of Utah School of Medicine.
According to the National Institutes of Health, psoriasis is a chronic skin disease of scaling and inflammation that affects 2 percent to 2.6 percent of Americans, or between 5.8 million and 7.5 million people. It occurs when skin cells quickly rise from their origin below the surface of the skin and pile up on the surface before they have a chance to mature. Psoriasis typically results in patches of thick, inflamed skin covered with silvery scales. They most often occur on the elbows, knees, other parts of the legs, scalp, lower back, face, palms, and soles of the feet.
Krueger and his colleagues originally thought that obesity was one of the causes of psoriasis. "That's not the case," he said. "What happens is that psoriasis develops and then obesity develops as a consequence."
In their study, the researchers looked at patients in the Utah Psoriasis Initiative (UPI) and compared them with three other population databases and with 500 adult patients who did not have psoriasis.
They found that 34 percent of the patients in the UPI were obese, compared with the 18 percent found in the general Utah population. Obesity was also more common in psoriasis patients than in patients who didn't have psoriasis.
The researchers also found that 37 percent of the patients in the UPI smoked, compared with 13 percent of patients in the general Utah population. Smoking seemed to be a causal factor in psoriasis, but many patients also took up smoking after they developed the condition, Krueger said.
"If you are not genetically predisposed to having psoriasis, one of the things that you can do to make sure that you get psoriasis is smoke," Krueger said.
The researchers aren't sure why psoriasis seems to be linked to obesity. "Do people with psoriasis have a poor self-image or sit around more, or drink more alcohol, or are depressed? We don't know," Krueger said.
The increase in smoking and obesity among people with psoriasis is creating public health issues, Krueger said. "These issues are the same as what are seen in the general population in those people who have increased body mass and smoke," he said. "These include cardiovascular disease and musculoskeletal problems."
Dr. Jeffrey M. Weinberg, the director of the clinical research center in the department of dermatology at St. Luke's-Roosevelt Hospital Center, in New York City, said the new findings will change his clinical practice.
"Having seen this data, warning patients not to smoke will become part of my regular evaluation and counseling," he said. "Cessation and avoidance of smoking should become a major lifestyle for our patients."
For more on psoriasis, visit the National Psoriasis Foundation.