The epidemiology of psoriasis is relatively well studied, and there is comprehensive research about the prevalence of the disease, severity of symptoms and health care costs. Each of these broad categories will be covered in more detail below.
Prevalence of Disease
Psoriasis affects approximately 125 million people on a global basis, which is 2.2% of the worldwide population. The prevalence varies in different areas of the world, however, with higher rates reported in developed countries accounting for 4.6% of the population. As a general observation, the prevalence of psoriasis is also higher among populations that live further away from the equator.
It is the most common autoimmune disease in the United States, with an estimated 7.5 million Americans that suffer from the condition. It has a strong hereditary link, with one in three patients that have a close family member with the condition.
The incidence of psoriasis is most common between the ages of 15 and 25, but may affect individuals of any age. Psoriatic arthritis typically develops ten years or more after diagnosis of psoriasis, between the ages of 30 and 50.
Psoriatic arthritis is a successive condition of psoriasis that affects between 10-30% of patients with psoriasis.
Severity of Symptoms
The severity of psoriasis varies significantly between different patients but for the majority of patients it presents a large problem for their everyday life. As expected, patients with a more severe form of the disease are more likely to report greater inhibition of daily life and activities.
Mild psoriasis is defined as affecting less than 3% of the body surface. Moderate psoriasis is defined as affecting less between 3-10% of the body surface. Severe psoriasis is defined as affecting more than 10% of the body surface. (As a guide, the palm of the hand is approximately 1% of the total body surface area.) Nearly 1 in 4 of patients with psoriasis have severe symptoms, which is more likely to has an impact on their quality of life.
It is common for psoriasis to impact the decisions and everyday lifestyle of affected individuals, with higher rates of obesity, alcohol consumption and smoking seen post diagnosis. This is likely associated with the comorbidities that are more likely to affect people with psoriasis, such as cardiovascular disease and Type 2 diabetes mellitus.
The total healthcare costs attributable to the management and treatment of psoriasis in the United States is calculated to the $135 billion each year. This includes direct costs, such as doctor’s visits and treatment, in addition to indirect costs such as absences from work and loss of productivity.