Scientists called epidemiologists study patterns of how diseases affect groups of people. For instance, epidemiologists are often called in to find out why an outbreak of a viral infection happens in a particular location or why one group of people may be more likely to get a certain disease than another group.
Epidemiologists also estimate how common a disease is. They determine the incidence of a disease, or how many new people are diagnosed with the disease each year, and the prevalence of a disease, or how many people in a population have the disease at any given time.
RA and other types of arthritis
Arthritis is a common health problem in the US population, affecting more than 54 million people, with this number expected to rise to 78 million in the next 20 years.1,2 Among chronic diseases in the US, arthritis causes more disability than any other condition, including heart disease, diabetes, and back or spine problems.1 RA is the third most common type of arthritis behind osteoarthritis (prevalence 31 million) and gout (prevalence over 8 million).3 RA affects over 1.3 million in the US.3,4
How common is RA among autoimmune diseases?
RA is one of the more common autoimmune diseases, with rates higher than a number of other conditions, including psoriasis, Crohn’s disease, Type I (insulin-dependent) diabetes, lupus, and multiple sclerosis.5
The prevalence of RA globally and in the US
RA is a common chronic disease that affects about 1% of the world population and about 0.6% of the American population.3,6 The annual incidence of RA has been estimated to be about 40 per 100,000. That means, each year, 40 new cases of RA will be diagnosed for every 100,000 people.7 RA often initially impacts individuals between 30 and 50 years of age, however, many children and older adults are impacted by the condition. About three-quarters of all individuals with RA are women.8
The burden of living with RA
Those with RA are more likely to have depression than those without the condition. Some data has shown that men with RA are hospitalized for depression more so than their counterparts without RA. Additionally, those with RA are more likely to be hospitalized for other conditions, like diabetes mellitus, than those without RA.3
Disability and costly medical expenses
It has been estimated that anywhere from 20 to 70 percent of working individuals with RA become disabled after seven to ten years, with up to half being unable to work within ten to twenty years. Nearly half of individuals with RA report struggling with medical bills, even after support from insurance, with younger individuals being the most burdened by medical expenditures. The total societal costs of RA have been estimated to be nearly $40 billion, which includes direct costs and indirect costs (including impacts to quality of life).3
Prevalence in different populations
The prevalence of RA varies widely from population to population, with the lowest rates in Asian countries and higher rates among certain Native American populations. This suggests that there is indeed some genetic component underlying susceptibility to the disease.9