Arthritis: The Facts

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Introduction

“Arthritis” literally means joint inflammation, but it is often used more broadly to describe any joint or connective tissue disorder. These diseases are also referred to as the rheumatic diseases of which over 150 different disorders have been described. This chapter presents information on osteoarthritis, rheumatoid arthritis, juvenile rheumatoid arthritis, gout and ankylosing spondylitis with additional material on osteoporosis.

The National Institute of Arthritis and Musculoskeletal and Skin Diseases considers arthritis the nation’s leading crippler: over 37 million Americans have one or more of the rheumatic diseases. A U.S. Health Interview Survey in 1974 showed that the activities of 4.4 million Americans were limited by arthritis and rheumatism. Approximately 1.5 million persons are completely work-disabled by rheumatic disease, and another 1.5 million are partially disabled. The Arthritis Foundation estimates that 26.6 million days are lost from work each year due to arthritis. The economic costs of arthritis, including medical expenses and lost wages, have been estimated at $6–$14 billion.

The arthritis disorders are a heterogenous group of diseases that have been the subject of intense investigation. Rheumatoid arthritis is thought to be an autoimmune response characterized by tissue inflammation and damage as a result of a reaction to immune complexes consisting of antibodies to IgG (rheumatoid factor) and IgM. Osteoarthritis, or degenerative joint disease, results from a wearing out of articular cartilage, especially in weight-bearing joints. Gout is associated with elevated serum uric acid levels that result in deposits of urate crystals in and around joints. Ankylosing spondylitis is a chronic inflammatory arthritis resulting in progressive immobility and consolidation of the spine. Juvenile rheumatoid arthritis is a diverse group of inflammatory disorders occurring in childhood, including arthritis and often systemic manifestations. Osteoporosis is a disorder characterized by a reduction in the density of bone that is frequently found in older adults.

Incidence and Prevalence

Osteoarthritis

Using data from the 1971-72 National Health and Nutrition Examination Survey (NHANES I) of adults ages 25-74 based on a medical examination and history only (no X-ray), it is estimated that 12.1% of the U.S. adult population or about 15.8 million persons have osteoarthritis.

The 1960-62 Health Examination Survey showed that 37% of the U.S. population aged 18-79 years had radiologic evidence of osteoarthrosis of the hands and/or feet.

A British survey indicated that 25% of workers with X-ray evidence of osteoarthrosis in the knee gave a history of knee pain, and the NHANES I indicated that 57% of people with evidence of severe osteoarthrosis of the hip reported significant hip pain on most days for at least a month.

Rheumatoid Arthritis

The most current national survey that examined individuals for rheumatoid arthritis was the 1960-62 Health Examination Survey (HES). Using revised American Rheumatism Association criteria, the HES survey revealed that 0.7% of males and 1.6% of females 18 years or older had classical or definite rheumatoid arthritis (RA). Based on 1985 population estimates, approximately .6 million males and 1.5 million females or a total of 2.1 million adults in the U.S. have classical or definite RA.

The natural history of rheumatoid arthritis indicates that 15% will have short-lived disease remitting without residua; 25% will have recurrent disease remitting with mild to moderate residua, 50% will have persistent disease leading to progressive deformity and 10% will have relentless disease, unresponsive to therapy, culminating in complete disability.

Rheumatoid arthritis patients have mortality rates (from all causes) that are about 1.5-2.0 times that of controls.

A 25-year study in the Rochester, Minnesota, area showed that the age-adjusted annual incidence of probable, definite or classical rheumatoid arthritis was 68.1 per 100,000 for females and 32.6 per 100,000 for males.

Gout

The overall prevalence of gout in the U.S. is estimated at 4.0 per 1,000, indicating that approximately 1,000,000 Americans suffer from gout.

90% of gout cases are primary or idiopathic resulting from defects in purine metabolism of unknown origin, while 10% are secondary resulting from the presence of another disease (renal failure, blood dyscrasia) or from the intake of drugs (salicylates, diuretics).

In 80%-90% of cases, the first attack of gout involves a single joint; in about 50% of cases the involved joint is the metatarsophalangeal joint of the big toe.

Ankylosing Spondylitis

It is estimated that between 300,000 and 500,000 Americans suffer from ankylosing spondylitis.

The annual incidence of ankylosing spondylitis has been estimated in males to be 1.1 per 10,000 and in females 0.4 per 10,000 among persons 15-74 years of age.

Estimates of the prevalence of ankylosing spondylitis in the U.S. range from 2 to 4 per 1,000 in males and 0.5 to 0.7 per 1,000 in females.

One study of patients with ankylosing spondylitis showed that 72% of patients had continuing exacerbations and remissions, while 28% of patients had progressive disability without remissions.

Juvenile Rheumatoid Arthritis

Estimates of the annual incidence of juvenile rheumatoid arthritis (JRA) range from 3 to 9 per 10,000 in persons under 16 years of age.

In 1985, it was estimated that 71,000 children under age 18 years in the U.S. had JRA; or 1.13 per 1,000 population.

JRA can be divided into three major subgroups: systemic-onset disease accounts for about 20% of patients; polyarticular-onset disease accounts for 30%-40% of patients; and pauciarticular disease accounts for about 40%-45% of patients.

About 75% of juvenile rheumatoid arthritis patients have long remissions with no permanent joint damage.

Osteoporosis

Osteoporosis is the most important underlying cause of fractures in the elderly. It has been estimated that 70% of fractures sustained by women 45 years of age and older in the U.S. are related to osteoporosis.

At about age 40, bone mass starts to decrease in all persons at varying rates. Eventually women may lose about one half and men about one quarter of the trabecular bone they had in earlier adulthood.

Risk Factor Prevalence

All Arthritis, Demographic Risk Factors

Age. According to a 1982 National Health Interview Survey (NHIS) 13.3% of Americans of all ages reported having arthritis. The reported prevalence of arthritis increased with age from 5.5% of those ages 1844, to 27.6% of those 45-64 and 49.6% of those 65 years and over.

Sex. The reported prevalence of arthritis is higher among females than males: under age 45, 4.2% of females reported having arthritis compared to 2.7% of males; of those 65 years and over, 55.7% of females and 40.7% of males reported having arthritis in the 1982 NHIS study.

Race. The reported prevalence of arthritis is similar among Blacks and whites: 3.4% of whites and 3.7% of Blacks under age 45 reported having arthritis; and 49% of whites and 52% of Blacks 65 years and over reported having arthritis in the 1982 NHIS study.

Osteoarthritis

Men and women in the U.S. are equally affected by osteoarthritis when all ages are considered; however, under age 45, the prevalence of osteoarthritis is greater in men, and over age 55, the prevalence is greater in women.

Heredity may play a role in the development of Heberden’s nodes (degenerative joint disease of the distal interphalangeal joints of the hands) as these lesions have been found to be twice as common among mothers and three times as common among sisters of affected women as in the general population.

Mechanical stress or wear and tear on joints may predispose to the development of osteoarthritis as evidenced by high prevalence rates of osteoarthritis in the elbows and knees of minors, in the fingers of cotton pickers, in the right hand of persons who are right-handed and in the stronger leg of persons with poliomyelitis.

Previous joint diseases or deformities can lead to osteoarthritis of the affected joint. Congenital dislocation of the hip or slipped capital femoral epiphysis may lead to osteoarthrosis of the hip. Ligamentous instability or torn cartilages may predispose to osteoarthrosis of the knee.

Rheumatoid Arthritis

Rheumatoid arthritis is two to three times more common in women than men. Although rheumatoid arthritis can begin at any age, the peak incidence is between 25 and 55 years. The prevalence of rheumatoid arthritis among first-degree relatives of patients with rheumatoid arthritis is about twice that of the general population.

Most studies indicate that age- and sex-specific prevalence rates for rheumatoid arthritis are approximately equal in Blacks and whites.

Rheumatoid arthritis occurs throughout the world: climate, geography, latitude and altitude have little influence on its prevalence. Certain populations, however, are noted to have a high prevalence (Pima Indians in Arizona) and others to have a low prevalence (Japanese and Puerto Ricans).

Rheumatoid factors are antibodies directed against a patient’s own gammaglobulins. Rheumatoid factors can be detected in about 2% to 5% of the general population and in about 10% to 25% of those diagnosed with rheumatoid arthritis.

Gout

A National Health Interview Survey (NHIS) showed that the reported prevalence of gout in the U.S. was nearly 3 times higher among men than women.

The NHIS study indicated that the reported incidence of gout increased with age from 4.1 per 1,000 of those ages 17-44 to 24.4 per 1,000 of those ages 65 and over.

The risk of gout increases with higher serum uric acid levels. A Framingham study showed that 1.1% of men with a uric acid level less than 6.0 (mg/100ml) developed gout over a 10-year period compared to 83.3% of men with a uric acid level greater than 9.0.

Normal serum uric acid levels are generally considered to be up to 7.0 mg/100ml in males and 6.0 mg/100ml in females. Using those values, one study in Michigan found a prevalence of hyperuricemia of 6.4% of males and 6.3% of females using a single determination.

Ankylosing Spondylitis

Ankylosing spondylitis is about three times more common in men than in women.

The age of onset of ankylosing spondylitis is most commonly between 15 and 35 years. The onset occurs earlier than age 15 in 10% of cases and later than age 50 in 5% of cases.

The human leukocyte associated (HLA) histocompatibility antigen B-27 is found in 88%-96% of Caucasian ankylosing spondylitis patients while it is found in 4%-8% of the general population.

About 20% of persons with the HLA B-27 antigen develop ankylosing spondylitis.

Family relatives of ankylosing spondylitis patients are 22 to 30 times more likely to develop the illness than relatives of individuals in comparison groups.

Juvenile Rheumatoid Arthritis

The prevalence rate of juvenile rheumatoid arthritis among females under age 18 years (2.0 per 1,000) is more than 6 times the rate for males (0.3 per 1,000).

For all three major subtypes of JRA patients (systemic, polyarticular and pauciarticular onset), the most frequent age of onset is between 1 and 3 years, with a second peak between 9 and 14 years.

Incidence and prevalence rates for juvenile rheumatoid arthritis vary little between whites and Blacks. However, a low frequency of JRA has been noted in Oriental children and a high frequency among Haida Indian Children of British Columbia.

Osteoporosis

In a Michigan study of women over age 45, the prevalence of osteoporosis based on X-rays of the lumbar spine was found to increase with age; 17.9% of women ages 45-49 had osteoporosis 57.7% of those ages 55-59; 73.5% of those ages 65-69 and 89.0% of those over age 75.

Osteoporosis affects women much more frequently than men and affects whites more commonly than Blacks. Osteoporosis-associated fractures occur less commonly in Black populations than in white populations.

Exogenous estrogen therapy inhibits bone resorption and preserves bone mass in oophorectomized women. Dietary elements such as calcium, vitamin D and fluoride, as well as physical activity, are thought by some to retard osteoporosis, although epidemiologic studies are needed.

Intervention Data

Health Services Utilization

In 1984, 2.4 million hospital discharges reported diseases of the musculoskeletal system and connective tissue as the first-listed diagnosis, including 536,000 discharges for arthropathies and related disorders and 509,000 discharges for intervertebral disc disorders.

Of the patients discharged from U.S. hospitals in 1984 with arthropathies and related disorders, 61.4% were female and 38.6% were male. 36.6% of those patients were 65 years and older. The average length of stay for those discharged for arthropathies and related disorders was 8.1 days in 1984.

In 1984, 164,000 knee replacement operations were performed in the U.S. 52% of these procedures occurred to males. 43% of knee replacement operations occurred to persons 15-44 years, 21% to those 45-64 years and 34% to those 65 and older.

184,000 hip replacement operations, were performed in the U.S. in 1984, with 71% occurring to females and 77% occurring to those age 65 and older.

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