Arthritis and Obesity among U.S. Adults

Jamie Zakkak
Advisor: C.M.G. Buttery, MD
Preceptor: Diane B. Wilson, EdD, MS, RD

Background: Arthritis interferes with quality of life, results in enormous medical and social costs, and is the leading cause of disability in the United States.  Overweight (including obesity) has been found to be associated with specific types of arthritis, but the relationship between excess body weight and arthritis in general has not been well characterized at the population level.  Furthermore, previous studies failed to utilize the CDC validated surveillance case definition of arthritis. 

Objectives:  To examine the association between body mass index (BMI: kg/m2) and arthritis using the CDC validated surveillance case definition of arthritis and to describe the prevalence of arthritis across population subgroups based on body mass index and other select characteristics.

Methods: Cross-sectional data from the 2005 Behavioral Risk Factor Surveillance System survey were analyzed.  Using population weights, descriptive statistics and prevalences were generated.  Univariate and multivariate analyses with 95% confidence intervals (CI) were conducted to examine the risk estimates (odds ratios/ORs) and to assess the relationship between body mass index and arthritis among U.S. adults, (N=356,112).  SAS 9.1 software was used for all analyses.

Results:  Overall, 26% of US adults had self-reported arthritis.  Obese persons (BMI: >30) were 2 times more likely to report arthritis compared to normal weight respondents, (BMI: < 25), and distinguishing among obese levels revealed an even greater association between BMI and arthritis. [Class III Obesity, (BMI: > 40): OR= 3.1, 95%CI= 2.9, 3.4; Class II Obesity, (BMI: 35-39.9): OR=2.4, 95% CI= 2.3, 2.6; Class I Obesity, (BMI: 30-34.9): OR= 2.0, 95% CI= 1.9, 2.1]  The association between the BMI groups and arthritis did not change significantly after taking demographic and socioeconomic variables into account. Older age, female gender, higher income, and lack of any physical activity were associated with a higher odds of reporting arthritis, while insurance status and being non-White were not.

Conclusions:  BMI is an important independent risk factor for self-reported arthritis.  Resources must be allocated to prevent and reduce weight gain in the population, especially among women and younger adults.