Walking Speed and Muscle Mass Estimated by the D3-Creatine Dilution Method Are Important Components of Sarcopenia Associated With Incident Mobility Disability in Older Men: A Classification and Regression Tree Analysis.
Jesse Zanker, Sheena Patel, Terri Blackwell and 10 others
PMID 32381425WHAT IT FOUND
In older men, walking speed under 0.88 m/s was the most important predictor of later mobility disability.
Estimated muscle mass and chair stand speed also predicted it. Grip strength and DXA lean mass did not.
Key findings
01Walking speed was the most important predictor of incident mobility disability; men with walking speed less than 0.88 m/s were more than 5 times more likely to develop it.
02When walking speed was excluded, D3 creatine muscle mass/weight (35%) and chair stands in 10 seconds (33%) were the most important predictors; 41.3% of men with chair stands less than 2.5 and D3 creatine muscle mass/weight less than 0.3 developed incident mobility disability.
03In the model that included walking speed, grip strength, DXA appendicular lean mass measures, total body fat, height, weight, BMI, and chair stands were not selected as nodes and had low variable importance.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The analysed sample was 1098 older men from MrOS, mostly white and community-dwelling, so the results may not apply to women, other racial or ethnic groups, or population-based samples. Many men were lost or excluded before analysis: 5994 were enrolled, but only 1098 were included in the tree analysis. Mobility disability was based on self-reported difficulty with walking 2 to 3 blocks, climbing 10 steps, and carrying or lifting 10 lb, not on observed performance. The D3 creatine dilution method is not approved for clinical use and requires urine collection 72 to 144 hours after ingesting labeled creatine. The paper states the walking speed and muscle mass cutpoints are not proposed as diagnostic criteria because the sample has limited generalizability. The model excluding walking speed was a separate exploratory analysis because walking speed is close to the mobility outcome. The supplied text contains an inconsistency in the model without walking speed: chair stands is described as the primary node, but also listed among variables not selected and low importance. CART does not consider patient factors such as inability to perform chair stands because of osteoarthritis, test availability, or cost-benefit ratios.
Declared interests
Research support is listed as NIH extramural and non-U.S. government. The supplied text does not include an author conflict-of-interest declaration.
The easy way to misread this
Do not treat the 0.88 m/s walking speed cutpoint as a diagnostic threshold or as proof that improving walking speed will prevent mobility disability. The paper says the cutpoints are not proposed for diagnosis, the sample was older mostly white community-dwelling men, and the D3 creatine muscle mass method is not approved for clinical use.