ARTHRITIS & RHEUMATISM
`Vol. 58, No. 1, January 2008, pp 15–25
`DOI 10.1002/art.23177
`© 2008, American College of Rheumatology
`
`Estimates of the Prevalence of Arthritis and
`Other Rheumatic Conditions in the United States
`
`Part I
`
`Charles G. Helmick,1 David T. Felson,2 Reva C. Lawrence,3 Sherine Gabriel,4
`Rosemarie Hirsch,5 C. Kent Kwoh,6 Matthew H. Liang,7 Hilal Maradit Kremers,4
`Maureen D. Mayes,8 Peter A. Merkel,2 Stanley R. Pillemer,9 John D. Reveille,8 and
`John H. Stone,10 for the National Arthritis Data Workgroup
`
`Objective. To provide a single source for the best
`available estimates of the US prevalence of and number
`of individuals affected by arthritis overall, rheumatoid
`arthritis, juvenile arthritis, the spondylarthritides, sys-
`temic lupus erythematosus, systemic sclerosis, and Sjo¨-
`gren’s syndrome. A companion article (part II) ad-
`dresses additional conditions.
`Methods. The National Arthritis Data Workgroup
`reviewed published analyses from available national
`
`The findings and conclusions in this report are those of the
`authors and do not necessarily represent the views of the Centers for
`Disease Control and Prevention, the National Institutes of Health, or
`the Department of Veterans Affairs.
`The National Arthritis Data Workgroup is a consortium of
`experts in epidemiology organized to provide a single source of
`national data on the prevalence and impact of rheumatic diseases. It is
`supported by the National Institute of Arthritis and Musculoskeletal
`and Skin Diseases, NIH; the National Center for Chronic Disease
`Prevention and Health Promotion and National Center for Health
`Statistics, CDC; the American College of Rheumatology; and the
`Arthritis Foundation.
`1Charles G. Helmick, MD: CDC, Atlanta, Georgia; 2David T.
`Felson, MD, MPH, Peter A. Merkel, MD, MPH: Boston University
`School of Medicine, Boston, Massachusetts; 3Reva C. Lawrence,
`MPH: NIH, Bethesda, Maryland; 4Sherine Gabriel, MD, MSc, Hilal
`Maradit Kremers, MD, MSc: Mayo Clinic, Rochester, Minnesota;
`5Rosemarie Hirsch, MD, MPH: CDC, Hyattsville, Maryland; 6C. Kent
`Kwoh, MD: University of Pittsburgh School of Medicine and Pitts-
`burgh VA Healthcare System, Pittsburgh, Pennsylvania; 7Matthew H.
`Liang, MD, MPH: Brigham and Women’s Hospital, Boston, Massa-
`chusetts; 8Maureen D. Mayes, MD, MPH, John D. Reveille, MD:
`University of Texas Health Science Center at Houston; 9Stanley R.
`Pillemer, MD: Macrogenics, Rockville, Maryland; 10John H. Stone,
`MD, MPH: Massachusetts General Hospital, Boston.
`Address correspondence and reprint requests to Charles G.
`Helmick, MD, Arthritis Program, CDC, 4770 Buford Highway, K51,
`Atlanta, GA 30341-3717. E-mail: CHelmick@cdc.gov.
`Submitted for publication June 7, 2007; accepted in revised
`form September 14, 2007.
`
`surveys, such as the National Health and Nutrition
`Examination Survey and the National Health Interview
`Survey (NHIS). For analysis of overall arthritis, we used
`the NHIS. Because data based on national population
`samples are unavailable for most specific rheumatic
`conditions, we derived estimates from published studies
`of smaller, defined populations. For specific conditions,
`the best available prevalence estimates were applied to
`the corresponding 2005 US population estimates from
`the Census Bureau, to estimate the number affected
`with each condition.
`Results. More than 21% of US adults (46.4 million
`persons) were found to have self-reported doctor-
`diagnosed arthritis. We estimated that rheumatoid ar-
`thritis affects 1.3 million adults (down from the estimate
`of 2.1 million for 1995), juvenile arthritis affects 294,000
`children, spondylarthritides affect from 0.6 million to
`2.4 million adults, systemic lupus erythematosus affects
`from 161,000 to 322,000 adults, systemic sclerosis af-
`fects 49,000 adults, and primary Sjo¨gren’s syndrome
`affects from 0.4 million to 3.1 million adults.
`Conclusion. Arthritis and other rheumatic condi-
`tions continue to be a large and growing public health
`problem. Estimates for many specific rheumatic condi-
`tions rely on a few, small studies of uncertain general-
`izability to the US population. This report provides the
`best available prevalence estimates for the US, but for
`most specific conditions, more studies generalizable to
`the US or addressing understudied populations are
`needed.
`
`In adults, arthritis is the leading cause of disabil-
`ity (1) and is among the leading conditions causing work
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`15
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`16
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`HELMICK ET AL
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`limitations (2). Over the next 25 years the number of
`people affected and the social
`impact of doctor-
`diagnosed arthritis are projected to increase by 40% in
`the US (3). Estimating the burden in the US population
`of the various rheumatic conditions that comprise arthri-
`tis is important for understanding their current and
`potential future impact on the health care and public
`health systems. Equally important is identifying the gaps
`in our understanding of burden.
`This and a companion article (4) update the
`National Arthritis Data Workgroup (NADW) reports of
`arthritis prevalence, our measure of burden, from 1989
`and 1998 (5,6). Sjo¨gren’s syndrome and carpal tunnel
`syndrome have been included for the first time, and
`additionally, the common symptoms of neck and back
`pain are addressed.
`
`METHODS
`
`The term “prevalence” has been defined and used in
`conflicting ways. In these 2 articles, we use prevalence to mean
`“prevalence proportion” (incorrectly called “prevalence rate”
`at times), meaning the proportion of persons in the population
`with the condition. We use the phrase “number affected” to
`refer to the absolute number of people affected in the popu-
`lation.
`
`US estimates of disease prevalence were usually based
`on data from published national or local population-based
`studies from the US and, if no accurate US data were available,
`from international studies. For overall arthritis, the number
`affected was based on the population sampled in the 2003–
`2005 National Health Interview Survey (NHIS). For other
`conditions, the best available prevalence estimates were ap-
`plied to the corresponding July 1, 2005 population estimates
`from the Census Bureau (http://www.census.gov/popest/
`national/asrh/NC-EST2005-sa.html) to estimate the number
`affected. Some of the US population-based studies were
`special studies in small areas that may not reflect the racial and
`ethnic profile of the US or of those affected by the illness.
`Caveats accompany the estimates presented, when there are
`concerns about generalizability.
`Several estimates came from 2 National Center for
`Health Statistics surveys: the NHIS and the National Health
`and Nutrition Examination Survey (NHANES). Both use
`probability samples of the US civilian, noninstitutionalized
`population to generate national health estimates. The
`NHANES uses interviews and examinations (e.g., physical
`examinations, laboratory tests, and radiographs) from ⬃5,000
`respondents annually. The much larger NHIS uses an annual
`cross-sectional, in-person interview survey of ⬃106,000 respon-
`dents in 43,000 households to collect self-reported health
`status information. Estimates for overall arthritis obtained
`using the NHIS were age adjusted to the projected 2000
`population age ⱖ18 years by 3 age groups (18–44 years, 45–64
`years, and ⱖ65 years) to allow better comparison of demo-
`graphic groups (available at http://www.cdc.gov/nchs/data/
`
`statnt/statnt20.pdf [used .530458, .299194, and .170271 from
`distribution 9, for ages 18–44, 45–64, and ⱖ65, respectively]).
`Measuring the prevalence of arthritis poses many
`challenges. From study to study, the distinction between point
`prevalence and cumulative (i.e., lifetime) prevalence is not
`always clear. Prevalence is difficult to determine for conditions
`that are episodic. Some conditions have no standard case
`definition, whereas others have competing or evolving case
`definitions based on different symptoms, signs, radiographic
`findings, or laboratory data. Estimates vary depending on the
`inclusion or exclusion of asymptomatic, mild, or early disease
`and the aggressiveness of case finding. Symptomatic individu-
`als in the community who do not seek treatment may go
`uncounted. Furthermore, individuals frequently do not know
`what specific rheumatic disease they have, so self-reported
`data cannot be used for estimates of specific conditions.
`
`RESULTS
`Overall arthritis. The case definition used to
`identify persons with arthritis has changed since our last
`report (6). In 1997 the NHIS stopped using condition
`lists and International Classification of Diseases, Ninth
`Revision, Clinical Modification (ICD-9-CM) codes, the
`basis of our previous method, and instead adopted new
`surveillance questions. Based on cognitive and valida-
`tion studies (7,8), “self-reported doctor-diagnosed ar-
`thritis” is thought to provide the most credible estimate
`of overall arthritis prevalence, with acceptable sensitivity
`and specificity for surveillance purposes. Respondents
`were defined as having doctor-diagnosed arthritis if they
`answered “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?” Among those with doctor-
`diagnosed arthritis, activity limitation attributable to
`arthritis was defined by a “yes” answer to the question,
`“Are you now limited in any way in any of your usual
`activities because of arthritis or joint symptoms?”
`The prevalence of
`self-reported doctor-
`diagnosed arthritis among adults age ⱖ18 years, esti-
`mated using the annual average from the 2003–2005
`NHIS surveys, was 21.6%, or 46.4 million (9) (Table 1).
`Although arthritis prevalence was higher in older age
`groups, with half of adults age ⱖ65 years being affected,
`nearly two-thirds of
`the adults reporting doctor-
`diagnosed arthritis were younger than 65 (Table 1).
`More than 60% were women. Age-adjusted arthritis
`prevalence was higher for women than for men (24%
`versus 18%) but was similar for non-Hispanic whites and
`African Americans (⬃22%), whose rates were higher
`than those for Hispanics (16.5%). The number of per-
`sons with doctor-diagnosed arthritis is projected to
`
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`PREVALENCE OF RHEUMATIC DISEASES IN THE US, PART I
`
`17
`
`Table 1. Unadjusted and age-adjusted estimates of the prevalence of and number affected by self-reported doctor-diagnosed arthritis and
`arthritis-attributable activity limitations among adults age ⱖ18 years, by sex, age, and race/ethnicity, National Health Interview Survey, United
`States, 2003–2005*
`
`Doctor-diagnosed arthritis
`(46.4 million affected)
`
`Arthritis-attributable activity
`limitation (18.9 million affected)
`
`Proportion with arthritis-
`attributable activity limitation
`among those with doctor-
`diagnosed arthritis
`
`Population,
`in 1,000’s
`
`Unadjusted
`% ⫾ 95% CI
`(no. affected)
`
`Age-adjusted
`% ⫾ 95% CI†
`
`Sex
`Men
`
`Women
`
`Age, years
`18–44
`
`45–64
`
`ⱖ65†
`
`Race/ethnicity
`White, non-Hispanic
`
`Black, non-Hispanic
`
`Hispanic
`
`Other non-Hispanic
`
`Total
`
`103,362
`
`111,411
`
`110,318
`
`70,019
`
`34,435
`
`153,148
`
`23,775
`
`26,904
`
`10,946
`
`214,772
`
`17.6 ⫾ 0.5
`(18.2 million)
`25.4 ⫾ 0.6
`(28.3 million)
`
`7.9 ⫾ 0.3
`(8.7 million)
`29.3 ⫾ 0.7
`(20.5 million)
`50.0 ⫾ 0.9
`(17.2 million)
`
`24.3 ⫾ 0.5
`(37.2 million)
`19.2 ⫾ 0.9
`(4.6 million)
`11.4 ⫾ 0.6
`(3.1 million)
`14.7 ⫾ 1.3
`(1.6 million)
`21.6 ⫾ 0.4
`
`18.1 ⫾ 0.5
`
`24.4 ⫾ 0.5
`
`–
`
`–
`
`–
`
`22.6 ⫾ 0.4
`
`21.4 ⫾ 0.9
`
`16.5 ⫾ 0.8
`
`17.3 ⫾ 1.3
`
`21.5 ⫾ 0.4
`
`Unadjusted
`% ⫾ 95% CI
`(no. affected)
`
`6.8 ⫾ 0.3
`(7.0 million)
`10.7 ⫾ 0.3
`(11.9 million)
`
`2.7 ⫾ 0.2
`(3.0 million)
`11.8 ⫾ 0.4
`(8.2 million)
`22.4 ⫾ 0.7
`(7.7 million)
`
`9.6 ⫾ 0.3
`(14.7 million)
`9.2 ⫾ 0.6
`(2.2 million)
`5.4 ⫾ 0.4
`(1.5 million)
`6.0 ⫾ 0.8
`(0.66 million)
`8.8 ⫾ 0.2
`
`Age-adjusted
`% ⫾ 95% CI†
`
`Unadjusted
`% ⫾ 95% CI
`
`Age-adjusted
`% ⫾ 95% CI†
`
`7.0 ⫾ 0.3
`
`10.3 ⫾ 0.3
`
`–
`
`–
`
`–
`
`8.9 ⫾ 0.3
`
`10.3 ⫾ 0.7
`
`8.2 ⫾ 0.6
`
`7.2 ⫾ 1.0
`
`8.8 ⫾ 0.2
`
`38.8 ⫾ 1.4
`
`42.3 ⫾ 0.9
`
`34.6 ⫾ 1.9
`
`40.3 ⫾ 1.2
`
`44.9 ⫾ 1.3
`
`39.5 ⫾ 0.9
`
`47.8 ⫾ 2.4
`
`47.6 ⫾ 2.6
`
`41.1 ⫾ 4.8
`
`40.9 ⫾ 0.8
`
`36.6 ⫾ 1.8
`
`39.0 ⫾ 1.2
`
`–
`
`–
`
`–
`
`36.4 ⫾ 1.2
`
`44.3 ⫾ 3.2
`
`45.2 ⫾ 3.2
`
`40.5 ⫾ 5.4
`
`38.1 ⫾ 1.0
`
`* See ref. 9.
`† Adjusted to the projected 2000 population age ⱖ18 years by 3 age groups: 18–44 years, 45–64 years, and ⱖ65 years (see ref. 88). 95% CI ⫽ 95%
`confidence interval.
`
`increase to nearly 67 million by 2030 (3)—an increase of
`⬃40%.
`Using the same report as was used to determine
`prevalence (9), we found that an estimated 8.8% of all
`US adults, or nearly 19 million persons, had arthritis-
`attributable activity limitations (Table 1). The preva-
`lence of activity limitations was higher in older age
`groups (affecting ⬎22% of all adults age ⱖ65 years),
`higher among women, and lower among Hispanics.
`Arthritis or joint symptoms led to activity limitation in
`⬎40% of adults with doctor-diagnosed arthritis. This
`outcome is projected to increase to 25 million (9.3% of
`the adult population) by 2030 (3).
`The high population prevalence of arthritis and
`of arthritis-related activity limitations translates into an
`immense personal and societal burden, often differing
`by race/ethnicity (10). This situation results in “arthritis
`and rheumatism” being the leading cause of physical
`disability in the US (1) and causes affected persons to
`have a substantially worse health-related quality of life
`
`(11). Among various other impact/burden measures,
`arthritis and other rheumatic conditions in 1997 were
`the underlying cause of death in 9,367 persons in the US
`(12), were present in 300,000 nursing home residents
`(19%) (13), and resulted in 744,000 hospitalizations (14)
`and 36.5 million ambulatory care visits (15). Costs of
`arthritis and other rheumatic conditions in 2003 were
`$128 billion (16).
`Rheumatoid arthritis (RA). RA is a multisystem
`disorder of unknown etiology, characterized by chronic
`destructive synovitis. Our previous national prevalence
`estimates for RA (6) were derived from the NHANES I,
`which used a case definition based on the clinical
`diagnosis by the examining physician. Since that time,
`classification criteria for RA have been revised (17–19).
`Several studies have provided estimates of the
`prevalence of RA in defined populations. Although
`these studies had a number of methodologic limitations
`(20), the remarkable finding was the uniformity of
`prevalence estimates in populations from different de-
`
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`

`18
`
`HELMICK ET AL
`
`66.8 years in 1995, suggesting that RA is becoming a
`disease of older adults. This observation, along with the
`expected rapid growth in the proportion of Americans
`age ⬎60 years, suggests that RA-associated morbidity,
`mortality, and disability are likely to increase among
`older adults.
`Using the 1995 Rochester, Minnesota age/sex-
`specific prevalence and the corresponding 2005 popula-
`tion estimates from the Census Bureau, we estimated
`that 1,293,000 American adults age ⱖ18 years (0.6%)
`have RA. This is lower than the previous estimate of
`2,100,000 (6) because of the decline in RA prevalence.
`These Rochester estimates are likely to be generalizable
`to the white US population, but their generalizability to
`other racial/ethnic populations is uncertain.
`Juvenile arthritis. The prevalence of chronic,
`inflammatory arthritis in children is difficult to estimate
`because of differences in nomenclature (e.g., “juvenile
`rheumatoid arthritis” [JRA], “juvenile chronic arthritis”
`[JCA], and most recently “juvenile idiopathic arthritis”
`[JIA]) and classification criteria (1977 American College
`of Rheumatology [ACR; formerly, the American Rheu-
`matism Association]
`[31], 1978 European League
`Against Rheumatism [32], and 1997 International
`League of Associations for Rheumatology [33] with a
`revision published in 2004 [34]), and the heterogeneity
`of the diseases and their subtypes encompassed under
`this rubric (35). In addition, variability in disease course
`among the subtypes of JIA may make it difficult to
`compare prevalence estimates for this condition across
`different study settings. In some types of the disease
`extended remissions occur, so that prevalence estimates
`include individuals who were ever affected, but are not
`currently affected.
`Prevalence reported in a comprehensive review
`ranged from 7 to 401 per 100,000 children across a broad
`diversity of geographic regions (35). Data from Roches-
`ter, Minnesota suggested declining prevalence, from
`9.43 per 100,000 children in 1980 to 8.61 per 100,000
`children in 1990 (36). These prevalences were lower
`than previous estimates from the same population,
`owing,
`in part, to differences in assignment of case
`definition.
`The combined incidence of JRA and juvenile
`spondylarthritis (“spondylarthritis” being a more con-
`temporary term for what is synonymously referred to in
`many earlier publications as “spondylarthropathy” [see
`below]) from other recent US and Canadian studies
`consistently ranges from 4.1 to 6.1 per 100,000, with the
`incidence of juvenile spondylarthritis ranging from 1.1 to
`2 per 100,000 (37–39). These studies have encompassed
`
`Figure 1. Prevalence of rheumatoid arthritis (adjusted to the 2000
`white US population) among female residents (A) and male residents
`(B) of Rochester, Minnesota at 4 time points (1965, 1975, 1985, and
`1995 [January 1 of each year]), by age group.
`
`veloped countries: ⬃0.5%–1% of the adult population.
`However, studies from the Pima Indian population
`showed significantly higher incidence and prevalence
`estimates (21).
`A study from Rochester, Minnesota showed a
`prevalence of RA in 1985 of 1.07% (95% confidence
`interval [95% CI] 0.94–1.20) among adults ⱖ35 years of
`age (22); this fell to 0.85% in 1995 (95% CI 0.75–0.95)
`(Gabriel S, et al: unpublished data). The prevalence
`among women in 1995 was approximately double that in
`men (1.06% versus 0.61%) (Gabriel S, et al: unpublished
`data).
`
`Trends in RA prevalence in Rochester, Minne-
`sota by age and calendar year show increasing preva-
`lence with older age and decreasing prevalence for most
`age groups in more recent time periods (Figure 1).
`These trends, by calendar year, age, and sex, have also
`been demonstrated in numerous other populations (21–
`26). In particular, the temporal decline in RA preva-
`lence is consistent with studies showing a progressive
`decline in RA incidence since the early 1960s (21,27–30).
`Also, the average age of persons with prevalent RA has
`increased steadily over time, from 63.3 years in 1965 to
`
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`PREVALENCE OF RHEUMATIC DISEASES IN THE US, PART I
`
`19
`
`Table 2. Prevalence of spondylarthritides, overall and by subtype
`
`Disease subtype
`
`Ankylosing spondylitis
`
`Psoriatic arthritis
`Enteropathic
`Peripheral
`Axial
`Undifferentiated spondylarthritis
`Overall spondylarthritides
`
`Group
`
`Ref.
`
`Male
`
`Female
`
`Total
`
`Prevalence per 100,000*
`
`Nationally representative (age ⱖ25 years men, ⱖ50 years women)
`Whites (age ⱖ15 years) men and women
`Blacks
`Eskimos (age ⱖ20 years)
`Whites (age ⱖ20 years)
`
`730
`200
`50–200
`400
`
`300
`70
`NA
`400
`
`48
`46
`47
`53, 61
`54
`
`56, 57
`57–59
`60, 61
`
`520
`130
`NA
`400
`101
`
`65
`50–250
`374†
`346–1,310‡
`
`* NA ⫽ not applicable.
`† The undifferentiated spondylarthritis estimate was derived by multiplying the frequency of the other spondylarthritides by 40% (assuming the
`maximum estimate for enteropathic arthritis) ([520 ⫹ 101 ⫹ 65 ⫹ 250] ⫻ 0.4 ⫽ 374).
`‡ The low range of overall spondylarthritides was derived by adding the total prevalence estimates for ankylosing spondylitis among whites, psoriatic
`arthritis, peripheral enteropathic arthritis, and the low estimate for axial enteropathic arthritis (130 ⫹ 101 ⫹ 65 ⫹ 50 ⫽ 346); undifferentiated
`spondylarthritis was excluded. The high range was derived by adding the total prevalence estimates for nationally representative ankylosing
`spondylitis, psoriatic arthritis, peripheral enteropathic arthritis, the high estimate for axial enteropathic arthritis, and undifferentiated spondylar-
`thritis (520 ⫹ 101 ⫹ 65 ⫹ 250 ⫹ 374 ⫽ 1,310).
`
`a number of diverse regions including New England;
`Manitoba, Canada; and 13 other centers across Canada.
`The prevalence of JCA from 2 Canadian studies was 3.2
`and 4.0 per 100,000 children (40).
`The prevalence of JRA in the US in different
`published reports ranged from 1.6 to 86.1 per 100,000.
`Data from the NHIS suggested a prevalence of 150 per
`100,000 for all types of childhood arthritis, including
`JRA, juvenile spondylarthritis, Lyme disease, arthritis
`associated with the less common pediatric connective
`tissue diseases, and other types of childhood arthritis.
`The prevalence of JCA (the name for JRA outside the
`US) found in a population-based study in Australia, in
`which respondents were surveyed door to door (41), was
`far higher (400 per 100,000) than has been found in
`other studies.
`In summary, there are very wide variations in the
`reported prevalences of chronic inflammatory arthriti-
`des of childhood, such as JRA and juvenile spondylar-
`thritis. The lack of comparable prevalence estimates
`across different regions in the US makes it difficult to
`estimate the total number affected. Perhaps the best
`prevalence estimates come via a novel approach using
`data from pediatric ambulatory care visits recorded in
`the 2001–2004 National Ambulatory and Medical Care
`Survey and the NADW ICD-9-CM case definition for
`adults (6) modified to reflect pediatric conditions, by
`which it was estimated that 294,000 children ages 0–17
`years (95% CI 188,000–400,000) were affected by the
`broadly defined “arthritis or other rheumatic condi-
`tions” (42).
`
`Spondylarthritides. The spondylarthritides (more
`contemporary term for what is synonymously referred to
`in many earlier publications as “spondylarthropathies”)
`are a family of diseases that includes ankylosing spon-
`dylitis (AS), reactive arthritis (formerly known as
`Reiter’s syndrome), psoriatic arthritis, enteropathic ar-
`thritis (associated with ulcerative colitis or Crohn’s
`disease), juvenile spondylarthritis, and undifferentiated
`spondylarthritis, which encompasses disorders express-
`ing elements of but failing to fulfill criteria for the
`above diseases. The prevalence of AS and other spondyl-
`arthritides parallels the frequency of
`the genotype
`HLA–B27.
`Ankylosing spondylitis. Among studies of white
`Europeans and East Asians, the reported prevalence of
`AS has varied between 30 per 100,000 and 900 per
`100,000 (reflecting differences in HLA–B27 frequency
`and in patient referral and disease ascertainment) (43–
`45). In the US, a 1979 study from Rochester, Minnesota
`showed a prevalence of 129 per 100,000 in a Caucasian
`population (46). Prevalence data suggest that AS occurs
`less frequently in African Americans than in whites (47).
`The overall prevalence of severe or moderate
`radiographic sacroiliitis on pelvic radiographs in men
`ages 25–74 years in the NHANES I was 730 per 100,000;
`among women ages 50–74 years, the prevalence was 300
`per 100,000 (48) (Table 2). Of those with moderate to
`severe radiographic sacroiliitis, only 7.6% were currently
`experiencing “significant pain in their lower backs on
`most days for at least one month.” Since questions
`
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`

`20
`
`HELMICK ET AL
`
`regarding inflammatory back pain (49) were not asked in
`this survey, the prevalence of AS cannot be ascertained.
`Reactive arthritis. The prevalence of reactive ar-
`thritis appears to be decreasing in developed countries
`(50). One study in Rochester, Minnesota investigated
`incidence (51), but prevalence in the general US popu-
`lation is unknown. Studies of American Indian groups
`have shown frequencies of 300 per 100,000 among
`Navajos (52) and 200–1,000 per 100,000 among Alaskan
`Yupik and Inupiat Eskimos (53), 2 groups with a high
`frequency of HLA–B27. Because many persons with
`reactive arthritis have remissions, prevalence estimates
`include individuals who were ever affected but are not
`currently affected.
`Psoriatic arthritis. In Olmsted County, Minnesota,
`the prevalence of psoriatic arthritis in 1992 was 101 per
`100,000 (95% CI 81–121 per 100,000) (54) (Table 2).
`There are no published data on its prevalence in African
`Americans or Hispanics.
`Enteropathic arthritis. The prevalence of inflam-
`matory bowel disease (IBD) in the US has been esti-
`mated to be 500 per 100,000 (55). However, the preva-
`lence of enteropathic arthritis/spondylitis has not been
`determined. The self-limited and nondestructive nature
`of peripheral enteropathic arthritis complicates calcula-
`tions of its prevalence (56), although it has been re-
`ported to occur in up to 13% of patients with IBD
`(57–59). Although inflammatory back pain occurs in up
`to 50% of patients with IBD (58,59), AS occurs in ⬍10%
`(57). Applying these percentages (13% for peripheral
`arthritis and 10–50% for spinal arthritis) to the preva-
`lence of 0.5% for IBD, the estimated US prevalence of
`enteropathic peripheral arthritis is 65 per 100,000 and
`that of enteropathic spinal arthritis ranges from 50 to
`250 per 100,000 (Table 2).
`Undifferentiated spondylarthritis. Limited data
`from Europe (60) and Alaska (61) suggest that ⬃40% of
`patients with spondylarthritis have “undifferentiated”
`spondylarthritis. Better population-based data are
`needed, especially from the mainland US, where the
`prevalence of this disorder has not been directly as-
`sessed.
`
`Overall spondylarthritis. The prevalence of spon-
`dylarthritis in the US is unknown. In studies of Euro-
`pean whites, the reported prevalence has varied widely,
`from 470 per 100,000 (60) to 1,900 per 100,000 (44).
`Higher prevalences in Eskimos from Siberia and Alaska
`have been reported (53). The prevalence of overall
`spondylarthritis in the US can be roughly estimated by
`summing either low or high prevalence estimates of its
`component subtypes, resulting in a range of 346–1,310
`
`per 100,000 among those age ⱖ25 years (Table 2). Using
`this range of prevalence and the corresponding 2005
`population estimates from the Census Bureau, we esti-
`mated that between 639,000 and 2,417,000 adults age
`ⱖ25 years have spondylarthritis.
`Systemic lupus erythematosus (SLE). SLE is a
`multisystem autoimmune disorder of unknown etiology,
`with disease manifestations that vary over time. The
`1982 ACR criteria for the classification of SLE (62),
`which are the most widely used, rely on signs and
`symptoms present at any time during a person’s illness.
`Patients with early or atypical disease often have not
`accumulated enough manifestations to meet criteria,
`and may not be counted.
`Studies of SLE prevalence have been performed
`in different regions of the country and have used varying
`methods of case identification, including screening of
`inpatient and outpatient records (63,64) and inferring
`prevalence on the basis of cases identified using multiple
`outpatient and hospital sources (65). In studies from a
`San Francisco, California health maintenance organiza-
`tion (HMO) and from Rochester, Minnesota, both
`involving predominantly white populations, SLE preva-
`lence was estimated to be 44 per 100,000 whites (63) and
`40 per 100,000 (mostly whites) (64,66), respectively. In a
`study from Nogales, Arizona, prevalence in Hispanic
`women was estimated to be 103 per 100,000 (67). A
`study from Hawaii showed a prevalence of 50 per
`100,000 among whites and persons of Japanese descent,
`versus 100 per 100,000 among persons of Chinese de-
`scent (68). In all of these studies, prevalence estimates of
`SLE among nonwhites were based on a limited number
`of cases, resulting in wide confidence intervals and
`limiting the precision of results.
`The estimated prevalence of SLE from the
`NHANES III was 53.6 per 100,000 among adults age
`ⱖ18 years and 100 per 100,000 among adult women,
`based on self-reported physician diagnosis and current
`prescription of medications used for SLE treatment
`(69).
`
`Among both whites and blacks, the prevalence of
`SLE is higher in women than in men. Using data from
`the San Francisco study (63), the prevalences in whites
`and African Americans among those ages 15–64 years
`were as follows: 100 per 100,000 white women, 400 per
`100,000 black women, 10 per 100,000 white men, and 50
`per 100,000 black men.
`Findings of one study suggest that the prevalence
`of suspected SLE is similar to that of definite SLE (66).
`For estimating SLE prevalence, we used a range that
`included the number of persons with definite SLE at the
`
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`PREVALENCE OF RHEUMATIC DISEASES IN THE US, PART I
`
`21
`
`low end and double that number at the high end, to
`include patients with suspected disease who do not meet
`strict ACR criteria for disease. Our reason was that the
`latter patients, like those who do meet the classification
`criteria, consume health resources and must cope with
`their illness, and many of them meet criteria later in
`their disease course (63,64,67–69). Using the San Fran-
`cisco sex/race prevalence among persons ages 15–64 and
`the corresponding 2005 population estimates from the
`Census Bureau, we estimated that as few as 161,000 and
`as many as 322,000 persons in the US have SLE (161,000
`definite SLE [11,000 white men, 80,000 white women,
`7,000 African American men, 56,000 African American
`women, and 7,000 people of other races]; 322,000 defi-
`nite or suspected SLE), although the generalizability of
`the San Francisco HMO data to the US population has
`not been determined.
`Systemic sclerosis (SSc; scleroderma). There are
`2 forms of SSc: a systemic form, which can have limited
`or diffuse skin involvement, and a localized form, which
`is confined to the skin and surrounding tissue. This
`report addresses only the systemic form.
`In a population-based study of SSc in southeast
`Michigan, prevalence was ascertained from multiple
`sources, including hospital discharge data, outpatient
`data from 2 academic centers, private-practice rheuma-
`tologists, and the local chapter of a scleroderma support
`group. Cases were defined as persons age ⱖ18 years who
`met the 1980 ACR preliminary criteria for the classifi-
`cation of SSc (70). Persons were also considered to be
`cases if they had a physician diagnosis and at least 2 of
`the 5 features of CREST syndrome (calcinosis,
`Raynaud’s phenomenon, esophageal dysmotility, sclero-
`dactyly, telangiectasias) (71). Seven hundred six SSc
`cases were identified and extrapolated to the US popu-
`lation, yielding a prevalence of 24.2 per 100,000 adults
`(95% CI 21.3–27.4) (72). Using capture–recapture meth-
`ods, an estimated number of missing cases was added,
`yielding a revised prevalence estimate of 27.6 cases per
`100,000 US adults (95% CI 24.5–31.0). Women were
`affected 4.6 times more frequently than men. SSc prev-
`alence had a modestly higher prevalence among African
`Americans than whites, with an age-adjusted prevalence
`ratio of 1.15 (95% CI 1.02–1.30). In addition, African
`Americans were significantly younger than whites at the
`time of diagnosis (mean ⫾ SD 41.0 ⫾ 14.6 years versus
`48.1 ⫾ 15.9 years; P ⬍ 0.001).
`The highest reported prevalence of SSc has been
`in a Choctaw Indian group in Oklahoma (66 cases per
`100,000, based on 14 cases) (73). There may be genetic
`
`factors that contribute to increased disease susceptibility
`in this group (74–76).
`A 20-year study of hospital-diagnosed sclero-
`derma cases in Allegheny County, Pennsylvania from
`1963 through 1982 suggested that disease incidence
`doubled over this period (77). However, recent data do
`not suggest any continued increase in incidence or
`prevalence (78).
`Using the southeast Michigan sex/race preva-
`lence and the corresponding 2005 population estimates
`from the Census Bureau, we estimated that 49,000
`Americans age 18 and older have SSc, although the
`generalizability of the Michigan data to the US popula-
`tion has not been determined.
`Primary Sjo¨gren’s syndrome (SS). SS may occur
`alone (primary SS) or with other autoimmune diseases,
`including RA or SLE (secondary SS). Prevalence esti-
`mates reported herein are confined to primary SS
`because there are insufficient data to evaluate the
`prevalence of secondary SS.
`Primary SS prevalence estimates have ranged
`from 0.05% to 4.8% across international communities
`(79–86), but only 3 of these studies (79–81) were
`population based. More recently reported prevalence
`rates have generally tended to be lower than those in
`earlier publications, which could reflect increasing rigor
`of epidemiologic studies, more restrictive and objective
`classification criteria, small sample sizes in earlier stud-
`ies, and selection biases. For example, in 1988, a preva-
`lence of 4.8% (95% CI 3.1–6.5%) was found in an
`elderly and institutionalized population (84), and in
`1989 a prevalence of 2.7% (95% CI 1.0–4.3%) was
`found in Swedish adults (85). Subsequent studies pro-
`vided lower SS prevalence estimates in Greek women
`(0.6% [95% CI 0.19–1.39%]) (81), in residents of Olm-
`sted County, Minnesota (0.32% cumulative incidence
`[which approximates prevalence]) (80), and in China
`