Growth patterns in early juvenile idiopathic arthritis: Results from the Childhood Arthritis Prospective Study (CAPS)

Abstract

Objectives: To investigate early vertical growth patterns and factors associated with poor growth in a modern inception cohort of UK children with juvenile idiopathic arthritis (JIA) using data from the Childhood Arthritis Prospective Study (CAPS).

Methods: A study period of 3 years was chosen. Children included in this analysis had a physician diagnosis of JIA and had height measurements available at both baseline and at 3-years of follow-up. Height is presented as z-scores calculated using World Health Organisation growth standards for age and gender. Growth over the 3-year period was assessed using change in z-score and height velocity. Univariable and multivariable linear regressions were used to identify factors associated with height z-score at baseline and change of height z-score at 3 years.

Results: 568 patients were included; 65% female, median baseline age 7.4 years [interquartile range (IQR) 3.6, 11.2], median symptom duration at presentation 5.5 months [IQR 3.1, 11.6]. Height z-score decreased significantly from baseline to 3 years (p ≤ 0.0001); baseline median height z-score was -0.02 (IQR -0.71, 0.61), decreasing to -0.47 (IQR -1.12, 0.24) at 3 years. Growth restriction, defined as change of height z-score ≤-0.5, was observed in 39% of patients. At 3 years, higher baseline height z-score was the strongest predictor for a negative change in height z-score [-0.3 per unit of baseline height z-score (95% CI: -0.36, -0.24), p < 0.0001].

Conclusions: Although overall height at 3 years after initial presentation to rheumatology is within the population norm, as a cohort, children with JIA experience a reduction of growth in height over the first 3 years of disease. Late presentation to paediatric rheumatology services is associated with lower height at presentation. However, patients with the lowest height z scores at presentation were also the most likely to see an improvement at 3 years. The impact of JIA on growth patterns is important to children and families and this study provides useful new data to support informed clinical care.

Keywords: Growth restriction; Height velocity; Juvenile idiopathic arthritis; Steroids; functional disability.

Fig. 1

Patient selection flowchart.

Fig. 2

Short stature: presented for the whole cohort and by ILAR subtype. ^†Short stature: height z score ≤ −2. Abbreviations: sJIA = systemic arthritis; RF = rheumatoid factor; ERA = enthesitis related arthritis; PSA = psoriatic arthritis.

Fig. 3

Average height velocity over 3 years of follow up by age at baseline (male and female). Median annual height velocity over the 3-year period plotted for each child and compared against age and gender matched reference population (WHO). Abbreviation: WHO = World Health Organisation.

Fig. 4

BMI classification at baseline and 3 years. BMI classification was defined using the Extended International (IOTF) Body Mass Index Cut-Offs for Thinness, Overweight and Obesity in Children. Abbreviations: BMI = body mass index; IOTF = International Obesity Task Force.