CDC reports increase in US adults hindered by arthritis;
Arthritis Foundation says obesity may be reason
CDC report: http://www.cdc.gov/mmwr



Morbidity and Mortality Weekly Report (MMWR)

Prevalence of Doctor-Diagnosed Arthritis and Arthritis-Attributable
Activity Limitation --- United States, 2007--2009
Weekly
October 8, 2010 / 59(39);1261-1265


Arthritis is a large and growing public health problem in the United
States (1), resulting in costs of $128 billion annually, and continues
to be the most common cause of disability (2). With the aging of the
U.S. population, even assuming that the prevalence of obesity and
other risk factors remain unchanged, the prevalence of doctor-
diagnosed arthritis and arthritis-attributable activity limitation
(AAAL) is expected to increase significantly by 2030 (1). To update
previous U.S. estimates of doctor-diagnosed arthritis and AAAL, CDC
analyzed National Health Interview Survey (NHIS) data from 2007--2009.
This report summarizes the results of that analysis, which found that
22.2% (49.9 million) of adults aged ≥18 years had self-reported doctor-
diagnosed arthritis, and 9.4% (21.1 million or 42.4% of those with
arthritis) had AAAL.

Among persons who are obese, an age-adjusted 33.8% of women and 25.2%
of men reported doctor-diagnosed arthritis. Arthritis and AAAL
represent a major public health problem in the United States that can
be addressed, at least in part, by implementing proven obesity
prevention strategies and increasing availability of effective
physical activity programs and self-management education courses in
local communities.

NHIS is an annual, in-person interview survey of the health status and
behaviors of the noninstitutionalized U.S. population of all ages. The
analysis described in this report used the sample adult component,
which is limited to persons aged ≥18 years. One adult per selected
household was chosen randomly to participate. Because NHIS oversamples
blacks, Hispanics, and Asians, persons in these populations aged ≥65
years have twice the probability of being selected, compared with
other adults. For this analysis, NHIS data from 2007, 2008, and 2009
were combined, and annualized prevalence estimates were calculated and
stratified by selected characteristics (i.e., sex, age group, race/
ethnicity, education level, body mass index (BMI) category,* physical
activity level,â€* and smoking status). Unweighted sample sizes were
23,393 in 2007; 21,781 in 2008; and 27,731 in 2009. Response rates for
the sample adult component were 67.8% in 2007, 62.6% in 2008, and
65.4% in 2009.§ Respondents were defined as having doctor-diagnosed
arthritis if they answered "yes" to "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?" Those
who responded "yes" to having doctor-diagnosed arthritis were asked
"Are you limited in any way in any of your usual activities because of
arthritis or joint symptoms?" Those responding "yes" to both questions
were categorized as having AAAL.

Statistical software was used to account for complex multistage
sampling design and produce weighted estimates and 95% confidence
intervals. Unadjusted prevalence was estimated to describe the actual
population burden; age-adjusted prevalence, standardized to the 2000
U.S. standard population, was estimated to facilitate comparisons
among demographic subgroups. For all comparisons, statistical
significance was determined using a two-sided t-test; differences were
considered statistically significant at p<0.05.

During 2007--2009, an estimated 22.2% (49.9 million) of U.S. adults
reported doctor-diagnosed arthritis. Arthritis prevalence increased
significantly with age. After adjustment for age, arthritis prevalence
was significantly higher among women (24.3%) than among men (18.2%);
those with less than a high school diploma (21.9%), compared with
those with at least some college (20.5%); persons who are obese
(29.6%), compared with normal/underweight (16.9%) and overweight
(19.8% ); physically inactive persons (23.5%) versus those meeting
physical activity recommendations (18.7%); and current (23.7%) or
former (25.4%) smokers, compared with never smokers (19.0%) (Table).
For all these comparisons, p values were <0.001.

During 2007--2009, an estimated 9.4% (21.1 million) of U.S. adults
reported AAAL. After adjustment for age, patterns of prevalence of
AAAL were similar to those for doctor-diagnosed arthritis (Table).

Among adults reporting doctor-diagnosed arthritis, the unadjusted
prevalence of AAAL was 42.4%. After adjustment for age, the greatest
prevalences were among persons categorized as obese class III (52.9%),
those with less than a high school diploma (52.0%), physically
inactive persons (51.2%), current smokers (47.6%), those categorized
as obese class II (46.7%), and non-Hispanic blacks (45.5%) (Table).

Among both men and women, age-adjusted arthritis prevalence increased
significantly with increasing BMI (p<0.001 for trend). The age-
adjusted prevalence among persons who are obese (25.2% for men, 33.8%
for women) was approximately double that for persons who are
underweight/normal weight (13.8% for men, 18.9% for women) (Figure).
Among those with arthritis, the age-adjusted prevalence of AAAL also
increased significantly with increasing BMI, from 34.7% for those who
are underweight/normal weight to 44.8% for those who are obese
(Table).

Reported by
YJ Cheng, MD, PhD, JM Hootman, PhD, LB Murphy, PhD, GA Langmaid, CG
Helmick, MD, Div of Adult and Community Health, National Center for
Chronic Disease Prevention and Health Promotion, CDC.

Editorial Note
Approximately one in five (49.9 million) adults in the United States
reported doctor-diagnosed arthritis during 2007--2009, and 21.1
million adults reported AAAL. The prevalence of arthritis and AAAL is
particularly high among persons who are obese. With the aging
population and continued high prevalence of obesity (3) in the United
States, the prevalence of arthritis is expected to increase
significantly over the next 2 decades.

Compared with previous estimates, the number of adults with arthritis
increased, but not significantly (p=0.07), from 46.4 million during
2003--2005 to 49.9 million during 2007--2009, an increase of
approximately 1 million adults per year (4). During the same period,
the prevalence of AAAL increased significantly (p=0.005), from 8.8%
(18.9 million persons) to 9.4% (21.1 million). The data on arthritis
prevalence appear consistent with a previous analysis that estimated
51.9 million adults would have arthritis by 2010 and 67 million by
2030 (1). That analysis also estimated that 19.1 million adults would
have AAAL by 2010 and 25 million by 2030; however, the findings in
this report indicate that 21.1 million persons already had AAAL during
2007--2009 (1).

Obesity is associated with onset of knee osteoarthritis (the most
common type of arthritis), disease progression, disability, total knee
joint replacement, and poor clinical outcomes after knee joint
replacement, and likely has a critical role in the increasing impact
of arthritis on disability, health-related quality of life, and health-
care costs (5). Lifetime risk for symptomatic knee osteoarthritis
alone is 60.5% among persons who are obese, double the risk for those
of normal/underweight (6). Because even small amounts of weight loss
(approximately 11 lbs [5 kg]) can reduce the risk for incident knee
osteoarthritis among women by 50% (7) and might also reduce mortality
risk in osteoarthritis patients by half (8), large-scale clinical and
community efforts to prevent and treat obesity as recommended by the
National Institutes of Health¶ might reduce the obesity-related burden
and impact of arthritis in the population.

The findings in this report are subject to at least four limitations.
First, doctor-diagnosed arthritis was self-reported and not confirmed
by a health-care professional; however, self-reports are sufficiently
sensitive for public health surveillance (9). Second, osteoarthritis,
rheumatoid arthritis, gout, lupus, and fibromyalgia have different
etiologies and risk factors; however, the public health
recommendations for these different types of arthritis are the same
(e.g., weight loss and increased physical activity), regardless of
differences in etiology or medical management. Third, because NHIS is
a cross-sectional survey, a cause-effect relationship between risk
factors (e.g., obesity) and arthritis and AAAL could not be
determined; certain risk factors, such as obesity, could develop after
onset of arthritis. However, prospective studies consistently have
identified excess body weight as a risk factor for incident arthritis,
particularly lower extremity osteoarthritis (5,7). Finally, because
all NHIS information is self-reported, underreporting of weight and
overreporting of leisure-time physical activity might have occurred
because of social desirability bias.

Both clinical treatment guidelines (10) and public health
recommendations for osteoarthritis** call for proven community-based
intervention strategies (e.g., self-management education, increased
physical activity, and weight management) to reduce pain and improve
physical function and health-related quality-of-life for persons with
osteoarthritis. Health-care providers and public health organizations
should work together to increase the availability of these
interventions for persons with all types of arthritis.

References
Hootman JM, Helmick CG. Projections of US prevalence of arthritis and
associated activity limitations. Arthritis Rheum 2006;54:226--9.
CDC. National and state medical expenditures and lost earnings
attributable to arthritis and other rheumatic conditions---United
States, 2003. MMWR 2007;56:4--7.
Flegal KM, Carroll MD, Ogden CI, Curtin LR. Prevalence and trends in
obesity among US adults, 1999--2008. JAMA 2010;303:235--41.
CDC. Prevalence of doctor-diagnosed arthritis and arthritis-
attributable activity limitation---United States, 2003--2005. MMWR
2006;55:1089--92.
Anandacoomarasamy A, Caterson I, Sambrook P, Fransen M, March L. The
impact of obesity on the musculoskeletal system. Int J Obes
2008;32:211--22.
Murphy L, Schwartz TA, Helmick CG, et al. Lifetime risk of symptomatic
knee osteoarthritis. Arthritis Rheum 2008;59:1207--13.
Felson DT, Zhang Y. An update on the epidemiology of knee and hip
osteoarthritis with a view to prevention. Arthritis Rheum
1998;41:1343--55.
Shea MK, Houston DK, Nicklas BJ, et al. The effect of randomization to
weight loss on total mortality in older overweight and obese adults:
the ADAPT Study. J Gerontol A Biol Sci Med Sci 2010;65:519--25.
Sacks JJ, Harrold LR, Helmick CG, Gurwitz JH, Emani S, Yood RA.
Validation of a surveillance case definition for arthritis. J
Rheumatol 2005;32:340--7.
Zhang W, Nuki G, Moskowitz RW, et al. OARSI recommendations for the
management of hip and knee osteoarthritis. Part III: changes in
evidence following systematic cumulative update of research published
through January 2009. Osteoarthritis Cartilage 2010;18:476--99.


* BMI = weight (kg) / height (m2). Categorized as follows: underweight/
normal weight (<25.0), overweight (25.0 to <30.0), obese (≥30.0),
obese class I (30.0 to <35.0), obese class II (35.0 to <40.0), obese
class III (≥40.0).

â€* Determined from responses to six questions regarding frequency and
duration of participation in leisure-time activities of moderate or
vigorous intensity and categorized according to the U.S. Department of
Health and Human Services 2008 Physical Activity Guidelines for
Americans. Total minutes (moderate plus 2 × vigorous) of physical
activity per week were categorized as follows: meeting recommendations
(≥150 min per week), insufficient activity (10--149 min), and inactive
(<10 min).

§ Information available at http://www.cdc.gov/nchs/nhis/quest_d...97_forward.htm.

¶ Available at http://www.nhlbi.nih.gov/guidelines/...y/ob_gdlns.htm.

** Available at http://www.cdc.gov/arthritis/docs/oaagenda.pdf .



What is already known on this topic?

Arthritis is a large and growing public health problem in the United
States, resulting in costs of $128 billion annually, and continues to
be the most common cause of disability.

What does this report add?

During 2007--2009, 22.2% of adults aged ≥18 years (49.9 million) had
self-reported doctor-diagnosed arthritis, and 9.4% (21.1 million or
42.4% of those with arthritis) had self-reported arthritis-
attributable activity limitation (AAAL). Among persons who are obese,
an age-adjusted 33.8% of women and 25.2% of men reported doctor-
diagnosed arthritis.

What are the implications for public health?

Arthritis and AAAL represent a major public health problem in the
United States that can be addressed, at least in part, by implementing
proven obesity prevention strategies and increasing availability of
effective physical activity programs and self-management education
courses in local communities.