Time trends in epidemiology and characteristics of psoriatic arthritis over 3 decades: a population-based study

Abstract

Objective: To determine time trends in incidence, prevalence, and clinical characteristics of psoriatic arthritis (PsA) over a 30-year period.

Methods: We identified a population-based incidence cohort of subjects aged 18 years or over who fulfilled ClASsification of Psoriatic ARthritis (CASPAR) criteria for PsA between January 1, 1970, and December 31, 1999, in Olmsted County, Minnesota, USA. PsA incidence date was defined as the diagnosis date of those who fulfilled CASPAR criteria. Age- and sex-specific incidence rates were estimated and age- and sex-adjusted to the 2000 US White population.

Results: The PsA incidence cohort comprised 147 adult subjects with a mean age of 42.7 years, and 61% were men. The overall age- and sex-adjusted annual incidence of PsA per 100,000 was 7.2 [95% confidence interval (CI) 6.0, 8.4] with a higher incidence in men (9.1, 95% CI 7.1, 11.0) than women (5.4, 95% CI 4.0, 6.9). The age- and sex-adjusted incidence of PsA per 100,000 increased from 3.6 (95% CI 2.0, 5.2) between 1970 and 1979 to 9.8 (95% CI 7.7, 11.9) between 1990 and 2000 (p for trend < 0.001). The point prevalence per 100,000 was 158 (95% CI 132, 185) in 2000, with a higher prevalence in men (193, 95% CI 150, 237) than women (127, 95% CI 94, 160). At incidence, most PsA subjects had oligoarticular involvement (49%) with enthesopathy (29%).

Conclusion: The incidence of PsA has been rising over 30 years in men and women. Reasons for the increase are unknown, but may be related to a true change in incidence or greater physician awareness of the diagnosis.

Figure 1. Annual incidence (per 100,000) of PsA by age and sex (1/1/1970-12/31/1999, Olmsted County, Minnesota)

Dotted lines represent smoothed incidence curves obtained using smoothing splines

Figure 2. Annual incidence (per 100,000) of PsA by calendar year and sex (1/1/1970-12/31/1999, Olmsted County, Minnesota)