CHAPEL HILL, N.C. - Adults age 45 and older who engaged in moderate physical activity up to two and a half hours a week did not increase their risk of developing knee osteoarthritis over a 6-year follow-up period, a new study finds.
Study participants who engaged in the highest levels of physical activity - up to 5 hours a week - did have a slightly higher risk of knee osteoarthritis, but the difference was not statistically significant.
Those findings taken together are good news, said Joanne Jordan, MD, MPH, senior study author and director of the Thurston Arthritis Research Center in the University of North Carolina School of Medicine.
"This study shows that engaging in physical activity at these levels is not going to put you at a greater risk of knee osteoarthritis," she said. "Furthermore, we found this held true no matter what a person's race, sex or body weight is. There was absolutely no association between these factors and a person's risk."
The corresponding author of the study, published online August 27 by the journal Arthritis Care & Research, is Kamil Barbour, PhD, of the Centers for Disease Control and Prevention (CDC) in Atlanta.
"Moderate physical activities are those that produce some increase in heart rate or breathing, like rapid walking," Barbour said. "Meeting physical activity recommendations through these simple activities are a great way to reduce your risk of heart disease, stroke, high blood pressure, diabetes, and other diseases."
The results are based on an analysis of data collected from 1999 to 2010 as part of UNC's long-running Johnston County Osteoarthritis Project, a prospective, population-based study of knee, hip, hand and spine osteoarthritis and disability in African Americans and Caucasians, aged 45 years and older. This project is funded by the CDC and the National Institute of Arthritis, Musculoskeletal, and Skin Diseases (NIAMS).
This new analysis included data from 1,522 study participants and tested whether or not there was an association between meeting Department of Health and Human Services (HHS) guidelines for 150 minutes of physical activity per week and the development of knee osteoarthritis, as confirmed both by X-rays and the presence of knee pain or other symptoms.
The study's findings support HHS recommendations and concludes that activities such as walking, conditioning exercises and household activities such as gardening or yard work that amount to moderate weekly levels of physical activity should continue to be encouraged.
Study authors from UNC are Joanne Jordan, MD, MPH and Jordan Renner, MD, from the School of Medicine; and Todd Schwartz, DrPH and Bill Kalsbeek, PhD, both from the UNC Gillings School of Global Public Health.
Authors from the CDC are Kamil Barbour, PhD, Jennifer Hootman, PhD, Charles Helmick, MD, Louise Murphy, PhD, and Kristina Theis, MPH.