The risk of psoriatic arthritis, a serious joint disorder, is greater than previously thought, with the annual number of people diagnosed increasing fourfold from 1997 to 2011. Researchers believe that doctors have become better at detecting the disease among people with psoriasis. However, doctors should focus more strongly on the fact that psoriasis is also associated with considerable increases in the risk of blood clots.
Psoriasis is one of the most common skin diseases, producing itchy rashes and dry skin. Although it cannot be cured, psoriasis may be brought to long-term remission with complete skin clearance, yet the people with psoriasis may also develop psoriatic arthritis, a disabling and incurable joint disease. Danish researchers are now the first to map the prevalence of and trends in the disease.
“The number of people diagnosed has increased massively, and especially more women have been diagnosed. Although we cannot be sure of the reason for this large increase, the results suggest that both doctors and people with psoriasis have become more aware of the symptoms of psoriatic arthritis,” explains Alexander Egeberg, main author and doctor at Gentofte Hospital.
Marked increase among women
The study was based on data from the Danish Patient Registry from 1997 to 2011, with 12,719 people diagnosed with psoriatic arthritis. In 1997, about 7 people per 100,000 individuals developed the disease each year in Denmark, but this incidence grew to 27 per 100,000 individuals in 2011 – an almost fourfold increase.
“We cannot exclude other reasons for the increase. However, since the number of people with psoriasis and those with other types of arthritis, such as rheumatoid arthritis, remained reasonably constant in the same period, the most likely explanation is that doctors diagnose the disease more frequently.”
The increase in the number of diagnoses is especially prominent among women. In 1997, equal numbers of men and women were diagnosed, but in 2011, 6 of 10 diagnosed with the disease were women.
“Again, we cannot exclude that specific genetic or environmental factors cause women to develop the disease more frequently, but the most likely explanation is simply that women are better than men at consulting their doctor when they develop symptoms of a disease.”
Alexander Egeberg and his colleagues will now delve more deeply into the numbers behind this remarkable increase to ensure that the increase has resulted from better diagnoses and not a real increase in the number of people with the disease.
“Our theory is that the more stringent criteria for diagnosing the disease – the classification criteria for psoriatic arthritis (CASPAR) – have made it homogeneous for doctors to diagnose psoriatic arthritis. Nevertheless, doctors have become much more aware of the importance of treatment because the new biological treatment methods are much more effective, and because, if left untreated, psoriatic arthritis results in irreversible joint damage.”
The risk increases for every year after diagnosis
This new study suggests a prominent trend in the treatment of psoriatic arthritis. It was previously treated with classic nonsteroidal anti-inflammatory drugs such as diclofenac or corticosteroids. Today there are more and more effective types of drugs, both chemical drugs and immunosuppressant biological drugs.
“With early and appropriate therapy, an ideal situation should be that the only reminder of their disease is that the patients must remember to take their medicine. This means in practice that the disease can be kept in check throughout long periods of time and that the people who were previously disabled can now lead a normal life and also be able to work normally as long as they start treatment promptly.”
This improvement in diagnosing and treating psoriatic arthritis is even more important given that researchers now estimate that 25–30% of people with psoriasis actually develop psoriatic arthritis. This is many more than previously estimated. Nevertheless, a new Danish-American study of 87,000 people with psoriasis in the United States in which Alexander Egeberg and his colleagues participated shows that the focus should be directed elsewhere.
“The study shows that the risk of cardiovascular disease and thrombosis rises by 1% for each year after someone develops psoriasis. This suggests that the disease and the constant inflammation contribute to putting the body under enormous pressure. And this suggests that doctors should focus more on precisely this aspect in the future.”
“Incidence and prevalence of psoriatic arthritis in Denmark: a nationwide register linkage study” has been published in Annals of the Rheumatic Diseases. “The relationship between duration of psoriasis, vascular inflammation, and cardiovascular events” has been published in the Journal of the American Academy of Dermatology. The Novo Nordisk Foundation awarded grants to co-authors Gunnar Hilmar Gislason (2012) and Lone Skov (2015), respectively, for the projects The Cardiovascular Quality of Care and Outcomes Initiative (CarQOI) and Optimization of Biological Treatment of People with Psoriasis.