This article is part of a series on The Scientific Basis of Rheumatology: A Decade of Progress, edited by Peter Lipsky and Ravinder Maini.

Review

Epidemiological studies in incidence, prevalence, mortality, and comorbidity of the rheumatic diseases

Sherine E Gabriel¹ and Kaleb Michaud^2,3

¹  Department of Health Sciences Research, Mayo Foundation, First St. SW, Rochester, MN 55905, USA

²  Nebraska Arthritis Outcomes Research Center, University of Nebraska Medical Center, Omaha, NE 68198, USA

³  National Data Bank for Rheumatic Diseases, N Emporia, Wichita, KS 67214, USA

author email corresponding author email

Arthritis Research & Therapy 2009, 11:229doi:10.1186/ar2669

Published:	19 May 2009

Abstract

Epidemiology is the study of the distribution and determinants of disease in human populations. Over the past decade there has been considerable progress in our understanding of the fundamental descriptive epidemiology (levels of disease frequency: incidence and prevalence, comorbidity, mortality, trends over time, geographic distributions, and clinical characteristics) of the rheumatic diseases. This progress is reviewed for the following major rheumatic diseases: rheumatoid arthritis (RA), juvenile rheumatoid arthritis, psoriatic arthritis, osteoarthritis, systemic lupus erythematosus, giant cell arteritis, polymyalgia rheumatica, gout, Sjögren's syndrome, and ankylosing spondylitis. These findings demonstrate the dynamic nature of the incidence and prevalence of these conditions – a reflection of the impact of genetic and environmental factors. The past decade has also brought new insights regarding the comorbidity associated with rheumatic diseases. Strong evidence now shows that persons with RA are at a high risk for developing several comorbid disorders, that these conditions may have atypical features and thus may be difficult to diagnose, and that persons with RA experience poorer outcomes after comorbidity compared with the general population. Taken together, these findings underscore the complexity of the rheumatic diseases and highlight the key role of epidemiological research in understanding these intriguing conditions.