CDC - Arthritis - Basics - Definition

Arthritis

Arthritis in General

The word arthritis actually means joint inflammation. The term arthritis is used to describe more than 100 rheumatic diseases and conditions that affect joints, the tissues which surround the joint and other connective tissue. The pattern, severity and location of symptoms can vary depending on the specific form of the disease. Typically, rheumatic conditions are characterized by pain and stiffness in and around one or more joints. The symptoms can develop gradually or suddenly. Certain rheumatic conditions can also involve the immune system and various internal organs of the body.

I. Background

Arthritis can be defined clinically, epidemiologically, or in other ways depending on the analyst's perspective. Here we use two standard approaches for defining arthritis:
- For estimating population prevalence using self-report surveys, we use the case definition of “doctor-diagnosed arthritis”—defined by answering ‘yes’ to the question “Have you EVER been told by a doctor or other health professional that you have some form of arthritis, rheumatoid arthritis, gout, lupus, or fibromyalgia?” This question is used by the Behavior Risk Factor Surveillance System (2002 and later) and the National Health Interview Survey (2002 and later). Because respondents are frequently not familiar with their specific types of arthritis, such self-report data are used only for the most generic definition of arthritis, where any misclassification is likely to occur between arthritis categories already included in the case definition.
- For estimates from health care system or other data using ICD-9-CM codes, we use a standard set of ICD-9-CM codes [53K] for “arthritis and other rheumatic conditions” (AORC) developed by the National Arthritis Data Workgroup in 1994.
Diagnosis. Most of these diseases are clinically diagnosed using the patient’s history, physical examination, and selected, supportive radiographic and laboratory studies. Only a few of these diseases (e.g., gout) have a definitive diagnosis.
Treatments. Non-inflammatory types are usually treated with pain medications, physical activity, weight loss (if overweight), and self-management education. Inflammatory types are treated with these modalities as well as anti-inflammatory medications (corticosteroids and nonsteroidal anti-inflammatory drugs (NSAIDs)), disease-modifying anti-rheumatic drugs (DMARDs), and a relatively new class of drugs known as biologic agents.

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II. Prevalence

About 21% of U.S. adults, or 46.4 million people aged 18 years or older, have self-reported doctor-diagnosed arthritis among the civilian, non-institutionalized population. (1)
Prevalence proportions for adults were higher among:
- Older adults (50% for persons aged >65 years, 29.3% for persons age 45–64 years, and 7.9% for persons aged 18–44 years). (1)
- Females (age-adjusted: 24.4% among women versus 18.1% among men). (1)
- Non-Hispanic whites and blacks (age-adjusted: 22.6% and 21.4%) versus Hispanics (16.5%) and other non-Hispanics (17.3%). (1)
- Obese and overweight people. Obese (age-adjusted: 29.3%) versus overweight (20.5%) or underweight/normal weight (17.4%). (1)
- Physically inactive people (age-adjusted: 22.3% for physically inactive versus 20.8% among physical active). (1)
About 8% of U.S. adults, or 18.9 million people aged 18 years or older, have arthritis attributable activity limitations 1 defined as a "yes" answer to "Are you now limited in any way in any of your usual activities because of arthritis or joint symptoms?"

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III. Incidence

Incidence data are not available.

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IV. Mortality

Mortality data for 20-year period 1979-1998 estimated 146,377 deaths with an underlying cause of arthritis and other rheumatic conditions (AORC). Deaths rose from 5537/year to 9367/year during that period, corresponding to an age-standardized annual rate of ~3/100,000. (2)
Deaths occurred among all age groups, including children; 12.1% occurred among persons aged 15–44. (2)
Age-standardized death rates were higher for women and blacks. (2)
Using 10 categories of AORC, three accounted for almost 80% of deaths: diffuse connective tissues diseases (34%; mostly systemic lupus erythematosus and systemic sclerosis), other specified rheumatic conditions (23%, mostly vasculitis), and rheumatoid arthritis (22%). (2)
During the 20-year period an additional 585,446 persons had AORC listed as an associated cause of death. (2)
These estimates may not capture mortality from treatment-related adverse effects, such as NSAID-induced gastrointestinal bleeds.

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V. Hospitalizations

An analysis of 2004 data from the Nationwide Inpatient Sample estimated 992,000 hospitalizations with a principal diagnosis of AORC. (3a)

A study using similar 1997 data showed that these people were older, had fewer comorbidities, had shorter stays, were more like to undergo a procedure, and were more likely to be discharged to short- and long-term care facilities than people with nonarthritis hospitalizations. The most common diagnoses and procedures related to osteoarthritis. This profile is consistent with a healthier-than-average hospital population electively admitted for specific procedures and subsequent rehabilitation. (3)
In 2004 there were an additional 3.6 million hospitalizations with AORC as a secondary diagnosis. (3a)

A study using similar 1997 data showed that these people were older, had more comorbidities, and a longer hospital stay than those with nonarthritis hospitalizations. This profile consistent with a sicker-than-average hospital population non-electively admitted for reasons other than their AORC, especially cardiovascular disease, with AORC complicating their hospitalization. (3)
More than 9% of all disease-related hospitalizations involved AORC. (3)

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VI. Ambulatory Care

Using 2004 data from the National Ambulatory medical Care Survey (NAMCS) and the National Hospital Ambulatory medical Care Survey (NHAMCS), there were an estimated 44.2 million visits for a primary diagnosis of AORC to physician offices (89%), and acute care hospital outpatient (6%) and emergency departments (5%). (3a)
For office visits the most frequent specialties involved were primary care physicians (45%) and orthopedic surgeons (36%). Other office staff involved in care included nursing staff (41%) and mid-level practitioners (3%). (3a)
Three of 11 AORC categories accounted for over 50% of visits: osteoarthritis and allied disorders (25%), joint pain/effusion/ other unspecified joint disorders (23%), and fibromyalgia (6%). (3a)
In a 1997 study using 1997 data, ambulatory care visits for AORC exceeded those for other common chronic conditions, such as cardiovascular disease and other circulatory diseases, essential hypertension, asthma/COPD/chronic bronchitis, cancer, and diabetes mellitus. (4) Persons of all ages made these visits, although the proportions were greatest among older ages; women had almost twice as many visits as men. (4)
In 2004, AORC was a secondary diagnosis in an additional 22.3 million ambulatory care visits. (3a)

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VII. Cost

Conservative analyses based on the 2003 Medical Expenditures Panel Survey (MEPS) estimated costs due to arthritis of $128 billion, up 48% from $86.2 billion in 1997 (or up 24% in constant 2003 dollars). The direct cost (medical expenditures) attributable to AORC were $80.8 billion and the indirect cost (earnings losses) were $47.0 billion. [These analyses adjusted for six demographic characteristics, nine expensive comorbidities, and health insurance status.] (5)
The largest components of direct costs were for ambulatory care (52.1%), inpatient care (20.0%), and prescription drugs (19.3%). (5)

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VIII. Impact on health-related quality of life (HRQOL)

No HRQOL measures exist that use either of the current arthritis case definitions listed above.
Analyses using a case definition roughly equivalent to “doctor-diagnosed arthritis OR possible arthritis”, although with slightly different questions, showed that adults with arthritis had significantly worse HRQOL than those without arthritis. This was true for self-reported fair/poor health (23.8 vs. 7.3%) and, in the past month, the number of physically unhealthy days (~5.0 vs. 1.0), mentally unhealthy days (~3.5 vs. 1.7), (physical or mental unhealthy days (~7.6 vs. 2.5), and activity limitation days (~3.0 vs. 0.7). (6)

Those especially affected were people in these categories: aged 45–64 years, blacks, Hispanics, separated marital status, less than a high school education, unemployed for more than one year, homemakers, those unable to work, the physically inactive, those who were underweight, those who lacked health care coverage or insurance, those who currently smoke, and those who did not drink alcohol. (6)

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IX. Unique characteristics

State specific prevalence estimates for 2007 and projections to 2030 for doctor-diagnosed arthritis and arthritis-attributable activities limitations are available.
These generic arthritis estimates are driven primarily by the most common type of arthritis—osteoarthritis.

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X. References

Hootman J, Bolen J, Helmick C, Langmaid G. Prevalence of Doctor-Diagnosed Arthritis and Arthritis-Attributable Activity Limitation—United States, 2003-2005. MMWR [View the errata for this article here and here.] 2006;55(40):1089–1092.
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: Data from the 1997 National Hospital Discharge Survey. Medical Care 2003;41(12):1367–1373.

3a. United States Bone and Joint Decade: The Burden of Musculoskeletal Diseases in the United States. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2008. Chapter 4. Arthritis and Related Conditions.
Hootman JM, Helmick CG, Schappert SM. Magnitude and characteristics of arthritis and other rheumatic conditions on ambulatory medical care visits, United States, 1997. Arthritis Rheum (Arthritis Care & Research) 2002;46(6):571–581.
Yelin E, Murphy L, Cisternas MG, Foreman AJ, Pasta DJ, Helmick CG. Medical care expenditures and earnings losses among persons with arthritis and other rheumatic conditions in 2003, and comparisons with 1997. Arthritis Rheum 2007;56(5):1397–1407.
Mili F, Helmick CG, Zack MM, Moriarty DG. Health related quality of life among adults reporting arthritis: Analysis of data from the Behavioral Risk Factor Surveillance System, US, 1996–1999. J Rheumatol 2003;30(1):160–166.
Freedman M, Hootman JM, Helmick CG. Projected State-Specific Increases in Self-Reported Doctor-Diagnosed Arthritis and Arthritis-Attributable Activity Limitations—United States, 2005–2030. MMWR [View the errata for this article here] 2007;56(17):423-425.