Background/Purpose Several studies published recently found that knee osteoarthritis (OA) is associated with an increased mortality in Caucasians. While prevalence of knee OA is higher in Chinese than Caucasians, no study has examined whether knee OA increases mortality in Chinese population.

Methods Between 8/2005-10/2005 1025 residents aged ≥ 50 years were recruited using door-to-door enumeration in randomly selected rural communities in Wuchuan, China. Subjects completed a home interview and had a hospital examination including weight-bearing posteroanterior semiflexed view of radiographs at TF joints and skyline view of radiographs at PF joints. We defined a knee as having whole ROA if either K/L score at TF joint ≥ 2 or presence of PFOA based on OARSI criteria. Symptomatic knee OA (SxOA) was recorded if both pain (i.e., knee pain occurred on most days in past month) and whole ROA were present at the same knee. Subjects were followed until November 31, 2013. Follow-up time for each subject was computed as the amount of time from the date of knee radiograph was obtained to the date of the first of the following events: death; the last date of contact; or the end of follow-up. All-cause mortality was calculated by dividing the number of deaths by the number of person-years of follow-up. We used a Cox-proportional hazard models to examine the relation of whole knee ROA and knee SxOA, respectively, to the all-cause mortality adjusting for age, sex, body mass index (BMI), education, income level, level of daily physical activity, and comorbidities.

Results Among 1025 participants (men: 49.3%, mean age: 55.5 years, mean BMI: 22.4 kg/m²) prevalence of whole knee ROA and SxOA at baseline was 17.7% and 6.2, respectively. For K/L grading, the weighted kappa for inter-rater reliability was 0.80 (95% confidence interval (CI): 0.72-0.88) and the intra-rater reliability was 0.92 (95% CI: 0.86-0.99). Over the follow-up period 99 subjects died. The mortality rate was higher among subjects with knee SxOA (32.6/1000 person-years) than those without SxOA (10.9/1000 person-years). After adjustment for age, sex and other potential confounders, subjects with knee SxOA had 90% higher mortality rate than those without SxOA (hazard ratio=1.9, 95% confidence interval(CI): 1.0-3.5). While mortality among subjects with whole knee ROA (20.1/1000 person years) was higher than those without it (10.5/1000 person-years), after adjusting for age, sex and other potential confounders the association was not statistically significantly (hazard ratio=1.2, 95% CI: 0.7-1.9) (Table).

Conclusion Knee SxOA was associated with an increased risk of all-cause mortality among the residents in the rural areas of China. Future studies to understand the mechanisms underlying this association are needed.

Knee OA status	No. of subjects	Follow-up years	No. of death	Mortality rate (1/1000 P-YRs)	Adjusted hazard ratio (95% CI)*
Presence of knee SxOA
No	962	7691.3	84	10.9	1.0 (reference)
Yes	63	460.8	15	32.6	1.9 (1.0,3.5)
Presence of ROA
No	844	6759.4	71	10.5	1.0 (reference)
Yes	181	1392.6	28	20.1	1.2 (0.7,1.9)

 * adjusted for age, sex, BMI, education, income level, level of daily physical activity, and comorbidities

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/knee-osteoarthritis-and-all-cause-mortality-the-wuchuan-osteoarthritis-study/