Epidemiology
of Adult Rheumatoid Arthritis.
Risk
factors
It is multi factorial disease with interaction of
both genetic and environmental factors. Exact cause is still unknown.
Gender.
It is 2-3 times more common in
women.
Age
Incidence of this disease
increases with age but it can occur at any age.
Genetic factors
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Persons with positive family
history of disease are more prone to develop this disease. It
Contributes about 60 % in aetiology of RA.[29].It shows that
environmental factors also contribute in aetiology of disease.
Socio-economic factors.
Some evidence in U.K. that poor
prognosis in socially deprived people.[13]
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Infectious agents.
Some infectious agents are
implicated but evidence is poor .The probable agents are Parvovirus,
rubella virus, Epstein-Barr virus, borrelia burgdorferi etc.[19]
Lifestyle.
Smoking is now established
risk factor. It also aggravate
the disease course .A study in Sweden concludes that smoking causes RF
positive RA in both sexes.[30]
Hormonal factors
As this disease is more common in
women so it seems that some hormonal factors might be involved. Many
studies have been done to know the relationship between oral contraceptive
pills and pregnancy with rheumatoid arthritis .
Spector TD did the case control study(1990)[31] and suggest
that oral contraceptives and parity is protective against rheumatoid arthritis. But
in the same year he did metaanalysis on protective effect of
OCP on RA[32] and he
select 6 case control and 3
longitudinal. studies and concluded that OCP might not have any protective
effect but may change the course of disease.
Prospective cohort
study[33] of 140 women were followed from last trimester of pregnancy and
6 months postpartum. This study concluded that there was little effect of
pregnancy on rheumatoid arthritis outcome plus great variability of
disease. Researcher criticise the previous studies and make argument that
many previous
studies were retrospective (recall bias) without any validated
methods and sample size was small.
This study was followed by
another study in Netherlands[34] and came up with same conclusions but
they followed cohorts for 12 years and ascertain that multiple pregnancies
and ocp use before symptoms was associated with good outcome (less
radiographic joint damage and a better functional level).
Dietary factors.
Some dietary factors also
been implicated as risk factors but the evidence is not strong .Some
dietary factors are also investigated for its beneficial role in
alleviating the symptoms of rheumatoid arthritis but according to
NICE guidelines [35]if we put patient on diet for long time the
patient will develop some nutritional deficiencies.
Fish oil ,olive oil are
beneficial for patients. [36][37][38]
Fasting and vegetarian diet also
improves the pain score. [39]
Tea ,coffee and caffeine
consumption .[40]
A cohort study was done in
Birmingham, USA, started in 1986 in older women
31,336 women from age range of
55-69 years were selected without rheumatoid arthritis . By 1997
156 cases of rheumatoid arthritis were diagnosed. Results show
the relative risk of 2.58,
95% CI 1.63-4.06 for women who consume >4 cups of decaffeinated coffee while for women with daily consumption of >3 cups of tea
show RR of 0.39, 95% CI
0.16-0.97) compared with women who were never drinker of tea.
Ethnicity
More common in native
Americans. But now there is evidence that incidence and prevalence is
decreasing in this group as well.[41]
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