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. 2015 Jan 14;5(1):e006450.
doi: 10.1136/bmjopen-2014-006450.

Epidemiology of psoriasis and palmoplantar pustulosis: a nationwide study using the Japanese national claims database

Kiyoshi Kubota  1 , Yukari Kamijima  1 , Tsugumichi Sato  2 , Nobuhiro Ooba  3 , Daisuke Koide  4 , Hajime Iizuka  5 , Hidemi Nakagawa  6
Affiliations

Epidemiology of psoriasis and palmoplantar pustulosis: a nationwide study using the Japanese national claims database

Kiyoshi Kubota et al. BMJ Open. .

Abstract

Objective: The primary objective was to estimate the national prevalence of psoriasis and palmoplantar pustulosis (PPP) in Japan. Secondary objectives were to determine (1) whether psoriasis and PPP disease activity varies by season, and (2) whether disease severity is associated with concurrent diabetes mellitus, hyperlipidaemia and hypertension.

Settings: Patients with a psoriasis or PPP diagnosis code between April 2010 and March 2011 were identified using a Japanese national database.

Participants: 565 903 patients with psoriasis or PPP were identified. No patient was excluded.

Primary and secondary outcome measures: National prevalence was calculated using census data. We estimated the difference in the proportion of patients who used healthcare services, as a proxy for disease activity, between the hot and cold seasons and the difference in the standardised prevalence of comorbidities between severe and mild disease. The measures were estimated separately for the two broad disease categories of psoriasis and PPP but not in all patients as planned because the two disease categories had major differences.

Results: The national prevalence of psoriasis and PPP was 0.34% (95% CI 0.34% to 0.34%) and 0.12% (0.12% to 0.12%), respectively. The difference in the proportion of patients who used healthcare services in the hot compared to the cold season was -0.3% (-0.5% to -0.1%) for psoriasis and 10.0% (9.8% to 10.3%) for PPP. The difference in the standardised prevalence between severe and mild psoriasis was 3.1% (2.7% to 3.4%), 3.2% (2.8% to 3.6%) and 5.1% (4.7% to 5.6%) for concurrent diabetes mellitus, hyperlipidaemia and hypertension, respectively. No significant difference in the prevalence of comorbidity was observed for PPP.

Conclusions: The national prevalence, seasonal variation in disease activity and prevalence of comorbidities in Japanese patients with psoriasis and PPP estimated in this descriptive study may be used as basic information for future studies.

Keywords: Japan; database; palmoplantar pustulosis.

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Figures

Figure 1
Figure 1
Prevalence of psoriasis and palmoplantar pustulosis (PPP) in the Japanese population. The prevalence of psoriasis and PPP in Japan was estimated by dividing the number of patients with a psoriasis or PPP diagnosis code by the size of the population according to the census of October 2010.
Figure 2
Figure 2
Use of healthcare services by patients with psoriasis and palmoplantar pustulosis (PPP). The proportion was estimated as the number of patients for whom a claim with a psoriasis or PPP diagnosis code was issued in each of the 12 months between April 2010 and March 2011 divided by the number of patients with psoriasis and PPP, respectively.
See this image and copyright information in PMC

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