Exploring disease comorbidities and temporal disease progression of psoriasis: an observational, retrospective, multi-database, cohort study

Comorbidities associated with psoriasis are well documented. However, few studies have explored the comorbidity trajectories that patients with psoriasis commonly experience over time. This study reports the 5-year comorbidity trajectories of patients with psoriasis. To determine the long-term comorbidity trajectories of patients with psoriasis in Denmark. This observational cohort study explored the Danish National Patient Registry (DNPR) between 1999 and 2013 to identify comorbidities diagnosed 5 years prior to or after a psoriasis diagnosis. Comorbidity occurrence in patients with psoriasis (psoriasis cohort) was compared with patients without psoriasis (the N group). Comparison groups, each the same size as the psoriasis cohort, were created by selecting random patients from the N group. If a comorbidity occurrence was higher in more than nine comparison groups than in the psoriasis cohort, it was not analysed and only comorbidities that occurred in ≥ 0·8% of the psoriasis cohort were analysed. The strength of association between a psoriasis diagnosis and a comorbidity diagnosis was measured using relative risk (RR). All psoriasis and comorbidity pairs that achieved RR > 1 (P < 0·001) (known as a Diagnosed Pair) were tested for directionality to identify the sequence of diagnoses using a binomial test. Diagnosed Pairs with a statistically significant direction (Bonferroni corrected P-value < 0·025) were then used to create comorbidity trajectory clusters 5 years before and after a psoriasis diagnosis. A total of 17 683 patients with psoriasis were compared with 10 000 comparison groups. A total of 121 comorbidities met the minimum criteria that ≥ 0·8% of the psoriasis cohort were diagnosed with the comorbidity within 5 years (before or after) of their psoriasis diagnosis. Thirty-eight of these comorbidities achieved RR > 1 (P < 0·001) with psoriasis, of which 19 achieved a significant direction from psoriasis to a comorbidity (including psoriasis to hypothyroidism), and four achieved a significant direction from a comorbidity diagnosis to a psoriasis diagnosis (including Crohn disease to psoriasis); four of five comorbidity trajectories with three sequential diagnoses achieved an RR > 1 (P < 0·001) and a significant direction from psoriasis to the first comorbidity to the second comorbidity (including psoriasis to hypertension to atrial fibrillation and flutter). Comorbidity trajectories may support clinicians in conducting disease risk analyses of pat