Age and Sex Specific Trends in Incidence of Juvenile Idiopathic Arthritis in Danish Birth Cohorts from 1992 to 2002: A Nationwide Register Linkage Study.

Isabel Cardoso,Fanney Thorsteinsdottir,Ina Olmer Specht,Berit Lilienthal Heitmann,Peder Frederiksen,Lars Erik Kristensen,Mina Nicole Händel

doi:10.3390/ijerph18168331

Abstract

This study reports age- and sex-specific incidence rates of juvenile idiopathic arthritis (JIA) in complete Danish birth cohorts from 1992 through 2002. Data were obtained from the Danish registries. All persons born in Denmark, from 1992–2002, were followed from birth and until either the date of first diagnosis recording, death, emigration, 16th birthday or administrative censoring (17 May 2017), whichever came first. The number of incident JIA cases and its incidence rate (per 100,000 person-years) were calculated within sex and age group for each of the birth cohorts. A multiplicative Poisson regression model was used to analyze the variation in the incidence rates by age and year of birth for boys and girls separately. The overall incidence of JIA was 24.1 (23.6–24.5) per 100,000 person-years. The rate per 100,000 person-years was higher among girls (29.9 (29.2–30.7)) than among boys (18.5 (18.0–19.1)). There were no evident peaks for any age group at diagnosis for boys but for girls two small peaks appeared at ages 0–5 years and 12–15 years. This study showed that the incidence rates of JIA in Denmark were higher for girls than for boys and remained stable over the observed period for both sexes.

Highlights

Juvenile idiopathic arthritis (JIA) is a disease that comprises a heterogeneous group of inflammatory arthritis phenotypes, which are characterized by arthritis of unknown origin in one or more joints that persists for more than 6 weeks and with onset before the age of 16 years [1,2]
This study reported incidence rates (ILAR criteria) of 9 and 16/100,000 children/year in two different areas in Denmark: east Denmark and Aarhus, respectively [9]
There were approximately 67,000 births per year, with equal sex distribution. Among those diagnosed with JIA, the incidence rate was higher for girls (29.9 (29.2–30.7)

Summary

Introduction

Juvenile idiopathic arthritis (JIA) is a disease that comprises a heterogeneous group of inflammatory arthritis phenotypes, which are characterized by arthritis of unknown origin in one or more joints that persists for more than 6 weeks and with onset before the age of 16 years [1,2]. Overall JIA is characterized by joint inflammation, but the course of the disease and its associated conditions depend on the subtype, severity of the disease and treatment given [6]. When the disease is not properly controlled, it may lead to joint destruction and physical disability [6,7]; and extra-articular manifestations, such as uveitis, which are not uncommon either [7]. This condition can greatly decrease quality of life, physical function and development [5], and impose a substantial burden for the affected children, their parents and society [1].

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