Why Is Osteoarthritis Increasing?
Written by Editor   
Thursday, September 21, 2017 03:13 PM
Knee osteoarthritis has more than doubled in prevalence since the mid-20th century after occurring at low frequencies since prehistoric times, a study has found.
Researchers from Harvard University and other centers concluded that rising levels of knee osteoarthritis may be the result of modifiable risk factors, such as high body mass index (BMI), and may be more preventable than previously thought.
Researchers studied cadaver-derived skeletal remains to investigate long-term trends in knee osteoarthritis prevalence in the United States and evaluate the effects of longevity and BMI on disease levels by comparing the prevalence among persons who lived in the 19th to early 20th centuries with persons in the late 20th to early 21st centuries. The researchers also analyzed knee osteoarthritis in a large sample of archaeological skeletons of prehistoric Native American hunter-gatherers and early farmers.
Diagnosis of knee osteoarthritis was based on visual identification of the presence of eburnation on the articular surfaces of the right or left distal femur, proximal tibia, or patella.
The study found that the prevalence of knee osteoarthritis was 16% in the postindustrial sample, but only 6% and 8% in the early industrial and prehistoric samples, respectively.  Its prevalence was 2.1-fold higher in the postindustrial sample than in the early industrial sample.  Females were more affected than males. After controlling for sex, knee osteoarthritis prevalence in the postindustrial sample was 2.6 and two times higher than in the early industrial and prehistoric samples, respectively.  Among postindustrial persons with knee osteoarthritis, 42% had the disease in both knees, which was a 2.5- and 1.4-fold higher proportion than in the prehistoric and early industrial samples, respectively
Age and BMI were positively associated with knee osteoarthritis prevalence, but at all ages, prevalence was at least twice as high in the postindustrial sample as in the early industrial sample, even after controlling for BMI.
The researchers characterized knee osteoarthritis as a condition that from an evolutionary perspective fits the criteria of a “mismatch disease” -- i.e., one that is more prevalent or severe because bodies are inadequately or imperfectly adapted to modern environments.  “Other well-studied mismatch diseases, such as hypertension, atherosclerotic heart disease, and type 2 diabetes, that also have become epidemic during the last few decades are strongly associated with knee OA, suggesting common causes and risk factors.”
Who better to help a body “adjust” to its modern environment than the DC?