Effects of Age, Period, and Cohort on the Incidence of Psoriasis in Spain: A 30-year Review (1990-2019).

ABSTRACT

AIM: This study aimed to investigate the effects of age, period, and cohort on the incidence of psoriasis in Spain from 1990 through 2019 using the Global Burden of Disease (GBD) database and age-period-cohort (A-P-C) analysis. METHODS: We conducted an ecological trend study to analyze the incidence rates of psoriasis in Spain from 1990 through 2019. Joinpoint Regression Program, Version 5.0.2 - May 2023; Surveillance Research Program, National Cancer Institute and National Cancer Institute A-P-C tools were used to identify trends and assess the effects of age, period, and cohort. RESULTS: From 1990 through 2019, an estimated 2.99 million cases of psoriasis were diagnosed in Spain, with a mean annual increase of 0.49%. Significant decreases in age-standardized incidence rates (ASIR) were reported for both sexes, with women consistently maintaining a slightly higher ASIR. Joinpoint analysis revealed multiple turning points in the downward trend, indicating periods of stabilization. A-P-C analysis demonstrated significant declines in both net (overall trend) and local drift (age-specific trends), indicating a broad decrease in the incidence of psoriasis across most age groups. While the risk of psoriasis increased with age, peaking in the 50-54 age group, it declined thereafter. Furthermore, the analysis revealed a continuous decline in risk from 1990 through 2019 for both sexes, with individuals born in the early 21st century exhibiting a significantly lower risk vs those born in the early 20th century. CONCLUSION: This study observed a slight decline in the reported psoriasis ASIR in Spain, potentially due to reduced exposure to risk factors. However, limitations in data and the complexity of factors influencing the incidence of psoriasis require further research.