Millions of Quality Years Lost to Knee Osteoarthritis
About 4 million quality-adjusted life years (QALYs) are lost due to knee osteoarthritis (OA), according to research funded in part by the Arthritis Foundation. The majority of this loss will be felt by people who are obese and diagnosed with knee OA.
Epidemiology BasicsQuality-adjusted life years: A way of measuring disease burden, including both the quality and the quantity of life lived. Each year in a person’s life is assigned a value of 1.0 for perfect health down to a value of 0 for death. Take, for example, a completely healthy person whose life expectancy is 10 years. If that person develops a disease or disability that brings his quality of life value down from a 1.0 to a 0.7, that person’s QALY would be 7 years. The person may live for the full 10 years, but his quality of life would have been reduced by 3 years.
A group of researchers from various universities around the country used National Health and Nutrition Examination Survey III (NHANES III) data to estimate the number of people age 60 years or older in the United States in the following categories: 1) no knee OA and no obesity; 2) symptomatic knee OA and no obesity; and 3) symptomatic knee OA and obesity. The team then took that information and used a validated computer model of the natural history of knee OA and OA progression to estimate the impact of the disease on those people’s lives.
The researchers estimated that a 68-year-old individual without knee OA who is not obese is expected to have a life expectancy of 10.57 years. A person with knee OA who is not obese would have a quality-adjusted life expectancy of 9.96 years (a reduction of 0.61 year). An obese person with knee OA would have a quality-adjusted life expectancy of 8.35 years (a reduction of 2.22 years).
Expanding that individual adjustment to the US population of persons greater than 60 years of age affected by symptomatic knee OA will rob healthy-weight Americans of approximately 1.4 million QALYs and it will rob obese Americans of approximately 2.5 million QALYs.
Lead author and Arthritis Foundation grant recipient, Elena Losina, PhD, says, “Substantial QALY losses due to knee OA and obesity underscore the importance of assessing quality of life in interventions focused on reducing the burden of knee OA and adding obesity control to management of patients with knee OA. Focused research is needed to develop effective long-term weight control interventions for persons affected by knee OA.”
Losina E, et al. Millions of quality-adjusted life years lost due to knee osteoarthritis (OA) in the US elderly population: the role of obesity. Abstract presented at American College of Rheumatology Annual Scientific Meeting. San Francisco, October 25-29, 2008.