Routine
data and descriptive studies .
Prevalence
is Approx 1% worldwide.
However the prevalence is not same across the world. Women are affected
2-3 times more than men. Prevalence increases
with age and sex differences diminish with increase in age. It affects all
races but it is more common in certain races like Pima Indians[4] (prevalence
5.3-6.0)
and
in the Chippewa Indians (6.8%)[5].
|
It is rare in rural parts of China, Hong Kong [6]
,Indonesia, Japan .One study fails to find
even a single case of Rheumatoid arthritis in Nigeria.[7]
Prevalence in Northern Europe and North America is 0.5
-1.1%.[9][10][11][12][13]Southern Europe=0.3-0.7%.[14][15]There is
higher incidence if we go from south to north Europe. Prevalence in
developing countries is 0.1
-0.5% [16][17]. But in India ,the prevalence of rheumatoid
arthritis is .75% ,is similar to the developed countries.
|
|
Reason
might be
north
Indian population is genetically closer to the Caucasians than to
other ethnic groups.[18]
Prevalence
and incidence rates of RA worldwide (cases per
100
inhabitants)
|
Population
|
|
Prevalence rates
|
Incidence rates
|
|
North America
|
• USA (general population)
|
0.9–1.1
|
0.02–0.07
|
|
|
• USA (native-Americans)
|
5.3–6.0
|
0.09–0.89
|
|
North Europe
|
• England
|
0.8–1.10
|
0.02–0.04
|
|
|
• Finland
|
0.8
|
0.03–0.04
|
|
|
• Sweden
|
0.5–0.9
|
|
|
|
• Norway
|
0.4–0.5
|
0.02–0.03
|
|
|
• Netherlands
|
0.9
|
0.05
|
|
|
• Denmark
|
0.9
|
|
|
|
• Ireland
|
0.5
|
|
|
South Europe
|
• Spain
|
0.5
|
|
|
|
• France
|
0.6
|
0.01
|
|
|
• Italy
|
0.3
|
|
|
|
• Greece
|
0.3–0.7
|
0.02
|
|
|
• Yugoslavia
|
0.2
|
|
|
South America
|
• Argentina
|
0.2
|
|
|
|
• Brazil
|
0.5
|
|
|
|
• Colombia
|
0.1
|
|
|
Asia
|
• Japan
|
0.3
|
0.04–0.09
|
|
|
• China
|
0.2–0.3
|
|
|
|
• Taiwan
|
|
0.3
|
|
|
• Indonesia
|
0.2–0.3
|
|
|
|
• Philippines
|
0.2
|
|
|
|
• Pakistan
|
0.1
|
|
|
Middle East
|
• Egypt
|
0.2
|
|
|
|
• Israel
|
0.3
|
|
|
|
• Oman
|
0.4
|
|
|
|
• Turkey
|
0.5
|
|
|
|
• Africa
|
0–0.3
|
|
TABLE
NO 2 TAKEN FROM [19]
Incidence
and prevalence of rheumatoid arthritis is decreasing
in developed world .[12][13] But especially in women not in men and
proposed causes are
Use
of oral contraceptives by females after 1960s .[20]
There
is decrease in severity of disease .[21][22]
Change
in classification criteria of rheumatoid arthritis .[23]
Birth
cohort effect.
Norfolk
study.[13]
The
first study in uk for prevalence of rheumatoid arthritis was done in 1958
by Lawrence JS.[24]Since then the classification criteria had changed and
to see whether there is any decrease in prevalence of disease Norfolk
study was conducted in
primary setting . By stratified randomisation
according to seven age and
gender bands,7050 patients were mailed and then positive responders for disease
were examined by rheumatologist. The overall response rate was 82%.
Sixty-six cases of RA were identified. Extrapolated to the population of
the UK, the overall minimum prevalence of RA is 1.16% in women and 0.44%
in men. If we look at fig.2 which compares
the data from both studies,
it is clear that prevalence in women is decreasing in all age groups
except in 75+group.but the prevalence in men had increased.
Figure
1 and 2 taken from [44]