The study is believed to be the first to objectively measure how the severity of psoriasis might influence a patient's mortality.
Lead author Dr. Megan H. Noe, of the Perelman School of Medicine at the University of Pennsylvania, and colleagues recently reported their results in the Journal of Investigative Dermatology.
Psoriasis is a disease triggered by abnormal immune system activity that leads to an excess production of skin cells. As a result, skin cells build up, causing patches of thick, dry, scaly skin.
The elbows, knees, scalp, lower back, face, palms, and the soles of feet are most commonly affected by psoriasis, but it can also affect other parts of the body, including the fingernails and toenails.
According to the American Academy of Dermatology, psoriasis affects around 7.5 million people in the United States. Around 20 percent of these individuals have moderate to severe psoriasis, where the condition covers at least 5 percent of their body.
Studies have indicated that people with psoriasis are at greater risk of developing a host of other conditions, or comorbidities, including cancer, depression, cardiovascular disease, diabetes, and liver disease.
For this latest study, Dr. Noe and colleagues sought to determine how the severity of psoriasis influences mortality risk.
Using BSA to measure psoriasis severity
The researchers came to their findings by analyzing information from a database in the United Kingdom, identifying 8,760 people with psoriasis and 87,600 people without the disease.
Setting this study apart from previous research, the team sent surveys to the physician of each patient to determine the body surface area (BSA) affected by psoriasis. Subjects were divided into groups of psoriasis severity based on this information.
Over an average 4 years of follow-up, the researchers calculated the number of deaths that occurred per 1,000 person-years. Person-years is a measure that combines the number of study participants with the length of time they took part in the study.
Death risk 1.79 times higher
The study revealed that there were 3.24 deaths per 1,000 person-years among participants without psoriasis, compared with 6.39 deaths per 1,000 person-years for subjects with severe psoriasis - defined as psoriasis that covers more than 10 percent of a patient's BSA.
After adjusting for potential confounders - such as obesity, smoking, and the presence of other severe medical conditions - the team found that the risk of death for patients with severe psoriasis was almost double that of patients without the condition, at 1.79 times higher.
The researchers note that further studies are required to determine the precise causes of death among patients with severe psoriasis.
In the meantime, their current study highlights an important measure of psoriasis severity that could help to predict potential health risks for patients.
"By using BSA, which we can evaluate in a patient's clinical visit, we can better understand which patients are at highest risk for future medical problems and need preventative care."
Dr. Megan H. Noe