546 CLINICAL REPORT
ActaDV ActaDV Advances in dermatology and venereology Acta Dermato-Venereologica
Duration of Psoriatic Skin Disease as Risk Factor for Subsequent Onset of Psoriatic Arthritis
Alexander EGEBERG 1 , Lone SKOV 1 , Claus ZACHARIAE 1 , Gunnar H . GISLASON 2 – 4 , Jacob P . THYSSEN 1 and Lotus MALLBRIS 5
1
Department of Dermatology and Allergy and 2 Department of Cardiology , Herlev and Gentofte Hospital , University of Copenhagen , Hellerup ,
3
The Danish Heart Foundation , 4 The National Institute of Public Health , University of Southern Denmark , Copenhagen , Denmark , and 5 Eli Lilly and Company , Indianapolis , IN , USA
It is unclear whether psoriasis is a progressive disease that requires early aggressive intervention . This population-based study identified patients with psoriasis and psoriatic arthritis ( PsA ). Survival analysis and Kaplan – Meier life table techniques were used . The study comprised 10,011 psoriasis patients ( severe n = 4,618 ), and 1,269 patients also had PsA . Incidence of PsA increased with duration of cutaneous symptoms ( p = 0.0001 ). Psoriasis diagnosed before age 20 or 30 years , respectively , suggested a lower risk of PsA than psoriasis diagnosed after age 50 years , yet age at first cutaneous symptoms did not predict development of PsA . No clear association with disease severity was found . PsA incidence appeared stable with longer duration of psoriasis , but further data are needed to firmly establish the relationship with age of psoriasis onset .
Key words : psoriasis ; psoriatic arthritis ; disease duration ; epidemiology .
Accepted Feb 20 , 2018 ; Epub ahead of print Feb 28 , 2018 Acta Derm Venereol 2018 ; 98 : 546 – 550 .
Corr : Alexander Egeberg , Department of Dermatology and Allergy , Herlev and Gentofte Hospital , Kildegårdsvej 28 , DK-2900 Hellerup , Denmark . E- mail : alexander . egeberg @ gmail . com
Cutaneous psoriasis ( henceforth “ psoriasis ”) is a manifestation of psoriatic disease , a chronic systemic inflammatory condition that affects 2 – 3 % of Europeans , and up to 8 % of populations in isolated parts of the northern Europe , in particular Scandinavia ( Norway ) ( 1 ). Plaque psoriasis ( psoriasis vulgaris ) is the most common form of psoriasis and is reported to account for almost 90 % of all cases ( 2 ). The majority of patients ( approximately 70 – 80 %) have mild disease , i . e . psoriasis that can be managed with topical treatment alone ( 2 , 3 ). Clinically , psoriasis is characterized by sharply demarcated hyperkeratotic and scaling plaques , which may be either localized or widespread , and a common extracutaneous manifestation includes psoriatic arthritis ( PsA ) ( 4 ).
Psoriasis and PsA frequently co-exist ( 5 , 6 ). Patients with PsA display increased inflammation of the peripheral joints and skeleton , and may also have extra-articular manifestations , such as enthesitis and other musculoskeletal manifestations ( 7 , 8 ). While severity and prevalence of the different disease manifestations in PsA can differ greatly , the clinical picture may sometimes overlap with that of seronegative rheumatoid arthritis and ankylosing spondylitis , making the diagnosis difficult ( 8 ). It is wellestablished that most patients with PsA develop psoriasis prior to onset of their arthritic symptoms , but the exact clinical relationship is insufficiently understood ( 9 ). For example , some studies have suggested a relationship between both severity and duration of psoriasis and the development of PsA , yet other reports have suggested that the incidence of PsA remains constant after the initial diagnosis of psoriasis ( 10 – 12 ). Nevertheless , on a population level the incidence of PsA is steadily increasing across all age groups ( 13 ). To date , predictors for development of PsA have been identified , including severe psoriasis , nail involvement , low educational level , and uveitis , few of which are modifiable ( 14 ). The incidence of PsA is highest among patients in their fifth decade , the male-to-female ratio is 1:1 , and the disease is most frequent among Caucasians ( 13 , 15 ). Obesity is a reasonably well-established risk factor for PsA among patients with psoriasis , yet while some studies have suggested that smoking , alcohol use , and the anatomical location of psoriasis may also be risk factors , the evidence for these are scarce and there is a need for additional studies to predict development of PsA in patients with psoriasis ( 16 ). We therefore examined the effect of duration of psoriasis on the risk of developing PsA in a nationwide cohort in Denmark .
METHODS Data sources and study population
Study approval was obtained from the Danish Data Protection Agency ( ref . 2007-58-0015 , int . ref . GEH-2014-018 , I-Suite 02736 ). Danish register-based studies are exempted from ethics committee and institutional review board approvals . We conducted and reported the study in accordance with the recommendations of the Strengthening the Reporting of Observational Studies in Epidemiology ( 17 ). All records , including source codes for the present study , are kept at secured and encrypted servers held by Statistics Denmark .
Individual-level information was linked from nationwide administrative registers using a unique and unambiguous personal identification number that all Danish residents are assigned at birth or migration . The Civil Registration System ( 18 ) contains information on sex , date of birth , and updated information on vital status and emigration , thus minimizing loss to follow-up . All inpatient and outpatient ( ambulatory ) hospital consultations are recorded doi : 10.2340 / 00015555-2912 Acta Derm Venereol 2018 ; 98 : 546 – 550
This is an open access article under the CC BY-NC license . www . medicaljournals . se / acta Journal Compilation © 2018 Acta Dermato-Venereologica .