One-half of the 14 million persons in the US with knee osteoarthritis (OA) are not physically active, despite evidence that physical activity (PA) is associated with improved health. We undertook this study to estimate both the quality-adjusted life-year (QALY) losses in a US population with knee OA due to physical inactivity and the health benefits associated with higher PA levels.
We used data from the Osteoarthritis Initiative and the Centers for Disease Control and Prevention to estimate the proportions of a US population with knee OA ages ≥45 years that are inactive, insufficiently active, and active, and the likelihood of a shift in their PA level. We used the OA Policy Model, a computer simulation of knee OA, to determine QALYs lost due to inactivity and to measure potential benefits of increased PA (comorbidities averted and QALYs saved).
Among 13.7 million persons with knee OA, a total of 7.5 million QALYs, or 0.55 QALYs per person, were lost due to inactivity or insufficient PA relative to activity over their remaining lifetimes. Black Hispanic women experienced the highest losses, at 0.76 QALYs per person. Women of all races/ethnicities had ~20% higher loss burdens than men. According to our model, if 20% of the inactive population were instead active, 95,920 cases of cancer, 222,413 of cardiovascular disease, and 214,725 of diabetes mellitus would potentially be averted, and 871,541 potential QALYs would be saved.
Physical inactivity leads to substantial QALY losses in a US population with knee OA. Increases in the activity levels in even a fraction of this population may have considerable collateral health benefits, potentially averting cases of cancer, cardiovascular disease, and diabetes mellitus.