People with psoriatic arthritis have healthcare costs, lower income, higher unemployment rates, higher risk for disability pension and more comorbidities than the general population.

Introduction
Psoriatic arthritis is a chronic inflammatory disease that affects a person’s joints, causing pain and disability. The disease often causes swelling of the fingers and toes, mainly because of joint inflammation. It gets its name from the link between this type of arthritis and a skin condition called psoriasis, which causes skin redness and scaling.

What did the authors hope to find?
The authors wanted to get a better understanding of what was going on before people developed psoriatic arthritis – for example, whether they had other disease or were unable to work.

Who was studied?
The study looked at 10,525 people with psoriatic arthritis and 20,777 people in the general population. There was no restriction on people’s age or gender. Everyone was living in Denmark. Data was collected from 1998 to 2014.

How was the study conducted?
This was a longitudinal nationwide study using information from databases in Denmark. This means there was no treatment or intervention being studied. The authors used the information in the databases to see how the societal costs, employment status, and occurrence of other disease in people with psoriatic arthritis both before and after diagnosis compared to people without psoriatic arthritis in the general population.

What were the main findings of the study?
The study found that people with psoriatic arthritis have higher healthcare costs, lower income, higher unemployment, and higher risk of being on a disability pension than people in the general population without psoriatic arthritis. 10 years after diagnosis, people with psoriatic arthritis were almost three-times more likely to be on a disability pension compared with people in the general population. They also found that before people with psoriatic arthritis are diagnosed, they have more other diseases than normal people in the general population. Once people have been diagnosed with psoriatic arthritis, they have higher healthcare and social costs, and more difficulty working than people without the disease.

Are these findings new?
The authors think that this is the first study of its kind in people with psoriatic arthritis.

What are the limitations of the study?
The study collected data from national databases. All doctors in Denmark are obliged to report data, including personal identity number and a coded diagnosis, on all inpatient and specialist outpatient visits. It is thought that the majority of entries are accurate, although figures for completing data are not as good for specialist outpatient visits to private clinics compared to public clinics. This could mean that there is information missing in these study results. However, the authors are confident that the large number of people included means that the results are reliable.

What do the authors plan on doing with this information?
This information has been presented at meetings and conferences, and more studies are planned to look at whether there is a link with other risks such as dying early.

What does this mean for me?
If you have psoriatic arthritis, you may have also been diagnosed with other diseases (sometimes called comorbidities), and you may find it difficult to work or to do the things you used to. There are treatments for psoriatic arthritis than can help you to function better. If you have concerns about your disease or your treatment, you should speak to your doctor.

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Date prepared: September 2017

Summary based on research article published on: 30 January 2017 From: Kristensen, LE. et al. Societal costs and patients’ experience of health inequities before and after diagnosis of psoriatic arthritis: a Danish cohort study. Ann Rheum Dis 2017;76:1495–1501. doi:10.1136/annrheumdis-2016-210579

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