Epidemiology

Understanding a chronic disease such as arthritis requires knowledge of how the disease affects people over their life span. This understanding will help identify potentially modifiable factors that can reduce the incidence (new cases) of and disability from arthritis. A critical scientific tool of public health, epidemiology, can help to develop the necessary knowledge to understand arthritis.

Although a great deal is known about arthritis, much more epidemiological information is needed to reduce the incidence of and disability from arthritis. For example, The National Arthritis Action Plan (NAAP) suggests that multiyear studies of the same people (with and without arthritis) are necessary to understand the risk factors that contribute to the development of arthritis and the effects of arthritis over a life span. Although a few modifiable risk factors are known for some types of arthritis, many others need to be identified to make a significant difference in the incidence and prevalence (total number of cases) of arthritis. Finally, knowing the personal impact of arthritis and how the various symptoms and long-term effects interact and cause disability can help suggest better ways of managing the disease.

We discussed the personal impact of arthritis in the Arthritis Basics section of this course. Here, we will present statistical information about the prevalence of arthritis, factors contributing to arthritis, disability, costs, healthcare utilization and mortality. We will also give information on modifiable risk factors. In addition, we will further describe questions for additional epidemiology study as outlined in the NAAP.

Estimating Arthritis Prevalence

For the purpose of estimating the population prevalence of arthritis, the CDC uses self-report data, specifically a "yes" response 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?” The best source for national arthritis prevalence estimates is the National Health Interview Survey (NHIS), an annual survey conducted by the National Center for Health Statistics. The Behavioral Risk Factor Surveillance System (BRFSS) is the best source for state arthritis prevalence estimates. Data from these and other surveys offer valuable information on arthritis related issues such as disability, limitations, body weight, health care utilization and health related quality of life. The estimated prevalence in each state varies, and depends, in part, on the age and gender distribution of the state's population.