CDC - Arthritis - Basics - Definition

Arthritis

Childhood Arthritis

I. Background

There is much disagreement among experts about definitions of childhood arthritis. At least three clinical classification schemes exist—juvenile rheumatoid arthritis (JRA), juvenile chronic arthritis (JCA), and juvenile idiopathic arthritis (JIA). All three schemes do not include many of the conditions considered as part of the larger rubric of arthritis and other rheumatic conditions in adults. Also, a case counted in one classification system may not be a case in another system; however, all schemes define childhood arthritis as occurring in people younger than 16 years.
Because childhood arthritis is an umbrella term covering a number of types of arthritis and because there are a number of different clinical case definitions for childhood arthritis, there is a wide range of estimates of how much childhood arthritis exists and much difficulty in describing its epidemiology.
The most common form of juvenile arthritis is JRA (the term and classification system used most commonly in the United States). JRA involves at least 6 weeks of persistent arthritis in a child younger than 16 years with no other type of childhood arthritis. JRA has three distinct subtypes: systemic (10%), polyarticular (40%) and pauciarticular (50%). Each type has a unique presentation and clinical course and immunogenetic association. For the latter two types, girls are more commonly affected (3–5:1). In all three types about 40–45% still have active disease after 10 years. For the systemic type, the peak age of onset is 1– to 6–years-old and about 50% of cases show very short stature in adulthood as a result. For the pauciarticular form, there are two distinct subtypes- early onset and late onset. Early onset is more common in girls, late onset is more common in boys. The genetics differ as do the clinical courses. In the polyarticular form, there are also two subtypes: rheumatoid factor (RF) positive and negative. RF positive usually affect girls with onset after 8 years of age and a poorer prognosis compared with RF negative children. (1)
For adults, more than 150 conditions are counted as arthritis and other rheumatic conditions (AORC). Many of these conditions occur in children, although much more rarely.

Top of Page

II. Prevalence

National Health Interview Survey (NHIS) data from 2001–2004 on parentally-reported doctor or other health care professional diagnosed arthritis among children younger than age 18 estimated an average of 80,100 cases (95% CI = 51,500–108,600).
NHIS data from 2001–2004 using 18 year-olds’ self reported prevalence of ever being told by a doctor or other health professional they had arthritis, rheumatoid arthritis, gout, lupus, or fibromyalgia yields an estimate of 119,600 (95% CI = 79,400–159,900). This estimate assumes that incidence has not changed in the 18 years since this cohort was born.
Applying prevalence rates of juvenile rheumatoid arthritis (JRA) from geographically proscribed, short term studies done in the United States² between 1975 and 1996 (rate range = 9.2–94.3 per 100,000 children) to the 2003 child population younger than 18 years of age yields estimates ranging from 11,700–69,000 cases of JRA in the United States. Applying those rates to the population under age 16, yields estimates between 10,300 and 60,900.
As a result of conflicting case definitions and varying prevalence estimates, the CDC, in collaboration with several other organizations, began an intensive review of options on how to estimate the number of children with arthritis and related conditions and also what conditions should be included. The study was prompted by a portion of the (proposed) Arthritis Prevention, Control, and Cure Act of 2004 which called for better determining the size of the childhood arthritis problem. The results follow.

A 2007 CDC study estimates that 294,000 U.S. children under age 18 (or 1 in 250 children) have been diagnosed with arthritis or another rheumatologic condition. This study provides for the first time a national data-based estimate of the number of children diagnosed with arthritis and related rheumatic conditions across the United States and within each state, creating a benchmark to measure future shifts in occurrence. (8)
In addition to providing these improved national estimates, the study also provides estimates for each state. CDC's first-ever estimates of childhood arthritis-related diagnoses show a state-by-state range from a low of 500 children in Wyoming to a high of 38,000 children in California. Study data also show that children diagnosed with arthritis and other rheumatologic conditions account for approximately 827,000 doctor visits each year, including an average of 83,000 emergency department room visits. (8) Read more about pediatric arthritis surveillance.
The 2007 CDC study estimates that among the estimated 294,000 children with arthritis or other rheumatic conditions (8), there were:
- 16,000 classified as rheumatoid arthritis and other inflammatory polyarthropathies.
- 92,000 with synovitis and tenosynovitis
- 67,000 with myalgia and myositis, unspecified

Top of Page

III. Incidence

There are no national studies of the incidence of juvenile arthritis.
Rates from geographically proscribed, short-term studies done in the United States between 1975 and 1996 yield incidence rate estimates ranging from 6.6–15 per 100,000 children, which translates into 4,800–11,000 new cases of childhood (under age 18) arthritis in the United States in 2003 and 4,300–9,700 in children under age 16. (2)
Overall, juvenile arthritis occurs more frequently in girls than boys. Family studies also suggest an increased risk for certain genetic make-ups.
Incidence rates vary by place. Even in one area, rates vary over time. These facts suggest an environmental component to the occurrence of juvenile arthritis.

Top of Page

IV. Mortality

Using codes for AORC as defined in adults, the Centers for Disease Control and Prevention’s (CDC) National Center for Health Statistics (NCHS) death data show that ~1,000 children younger than 15 years of age died from arthritis and other rheumatic conditions in the 20 years from 1979–1998 (average = 50 deaths / year).³The juvenile AORC death rate fell 25% during the 20-year period from 1.2 per million to 0.9 per million (average = 1 death per million children per year).

Top of Page

V. Hospitalizations

Using codes for AORC as defined in adults, in 1997, among children <14 years, there were 21,000 hospitalizations with principal diagnosis of AORC (rate = 3.5/10,000) and 33,000 hospitalizations with any mention of AORC (rate = 9.2/10,000) out of 2,266,000 childhood hospitalizations (0.9%–1.45% of all hospitalizations). (4)

Top of Page

VI. Ambulatory Care

Using codes for AORC as defined in adults, National Ambulatory Medical Care Survey (NAMCS) and National Hospital Ambulatory Medical Care Survey (NHAMCS) found that among children <17 years in 1997-98, there was an average of 1.3 million AORC-related ambulatory care visits per year. (5)
- Pediatric arthritis-related visits were more likely to be made by girls (67%), whites (82%), non-Hispanics (66%) and children aged 12–17 years (59%). Most visits occurred in physician offices (75%) compared to outpatient departments (18%) and emergency departments (7%). (5)
- Top three conditions were: soft tissue disorders excluding back (41%; 513,000), unspecified joint pain/effusion (31%; 387,000), and rheumatoid arthritis (10%; 122,000). (5)
- Among physician office visits, the medical specialties most commonly seen were family practice / general practitioners / internal medicine (41%), rheumatologists / orthopedists / neurologists (33%), while the rest (26%) saw pediatricians. (5)
Using the same data source but a different definition of childhood arthritis, a 2007 CDC study’s data show that children diagnosed with arthritis and other rheumatologic conditions account for approximately 827,000 doctor visits each year, including an average of 83,000 emergency department room visits. (6) Further information on the pediatric arthritis surveillance is available.

Top of Page

VII. Costs

The economic impacts of JRA appear substantial with national direct costs in 1989 estimated at $285 million. (7)

Top of Page

VIII. Impact on Health-related Quality of Life

Depending on the specific condition, the impact on quality of life can be considerable. For example, for systemic type JRA, about 50% of cases develop short stature (<5th percentile) in adulthood. Overall, about 30% of people with JRA had significant functional limitations 10 or more years after onset. (1)

Top of Page

IX. Unique characteristics

Transient childhood arthritis may follow certain infectious diseases.
Many cases of childhood arthritis remit.

Top of Page

X. References

Klippel JH , ed. Primer on the Rheumatic Diseases. Edition 12. Arthritis Foundation, Atlanta, GA;2001.
Manners PJ, Bower C. Worldwide prevalence of juvenile arthritis why does it vary so much? J Rheum 2002;29:1520–1530.
Sacks JJ, Helmick CG, Langmaid G. Deaths from arthritis and other rheumatic conditions, United States, 1979–1998. J Rheumatol 2004;31:1823–1828.
Lethbridge-Cejku M, Helmick CG, Popovic JR. Hospitalizations for arthritis and other rheumatic conditions. Med Care 2003;41:1367–1373.
Hootman JM, Helmick CG. Pediatric Arthritis-Related Ambulatory Medical Care Visits, United States, 1997–98, abstract for ACR will appear in supplement of Arthritis and Rheumatism).
Sacks JJ, Helmick CG, Luo YH, Ilowite NT, Bowyer S. Prevalence of and annual ambulatory health care visits for pediatric arthritis and other rheumatologic conditions in the United States in 2001–2004. Arthritis Care Res 2007;57(8):1439–1445.
Allaire SH, DeNardo BS, Szer IS, Meenan RF, Schaller J. The economic impacts of juvenile rheumatoid arthritis. J Rheumatol 1992;19:952–955.
Sacks JJ, Helmick CG, Luo YH, Ilowite NT, Bowyer S. Prevalence of and annual ambulatory health care visits for pediatric arthritis and other rheumatologic conditions in the United States in 2001–2004. Arthritis Care Res 2007;57(8):1439–1445. abstract