BACKGROUND: Psoriasis and periodontitis are chronic inflammatory disorders with overlapping inflammatory pathways, but data on risk of periodontitis in psoriasis are scarce and a possible pathogenic link is poorly understood.

OBJECTIVE: We investigated the association between psoriasis and periodontitis in a nationwide cohort study.

METHODS: All Danish individuals aged ≥18 years between 1 January 1997 and 31 December 2011 (n = 5,470,428), including 54 210 and 6988 patients with mild and severe psoriasis, and 6428 with psoriatic arthritis, were linked through administrative registers. Incidence rate ratios (IRRs) were estimated by Poisson regression.

RESULTS: Incidence rates of periodontitis per 10 000 person-years were 3.07 (3.03-3.12), 5.89 (1.07-6.84), 8.27 (5.50-12.45) and 11.12 (7.87-15.73) for the reference population, mild psoriasis, severe psoriasis and psoriatic arthritis respectively. Adjusted IRRs were (1.66; 1.43-1.94) for mild psoriasis, (2.24; 1.46-3.44) for severe psoriasis and (3.48; 2.46-4.92) for psoriatic arthritis. Similar results were found when a case-control design was applied.

CONCLUSIONS: We found a significant psoriasis-associated increased risk of periodontitis, which was highest in patients with severe psoriasis and psoriatic arthritis.