A modifiable risk factor?
Higher appendicular lean mass was associated with higher levels of cognitive performance, with each SD increase in lean mass associated with an SD increase in cognitive performance (OR, 0.09; 95% CI, 0.06-0.11; P = .001).
“Adjusting for potential mediation through performance did not reduce the association between appendicular lean mass and risk of AD,” the authors wrote.
They obtained similar results using genetically proxied trunk and whole-body lean mass, after adjusting for fat mass.
The authors noted several limitations. The bioimpedance measures “only predict, but do not directly measure, lean mass.” Moreover, the approach didn’t examine whether a “critical window of risk factor timing” exists, during which lean mass might play a role in influencing AD risk and after which “interventions would no longer be effective.” Nor could the study determine whether increasing lean mass could reverse AD pathology in patients with preclinical disease or mild cognitive impairment.
Nevertheless, the findings suggest “that lean mass might be a possible modifiable protective factor for Alzheimer’s disease,” the authors wrote. “The mechanisms underlying this finding, as well as the clinical and public health implications, warrant further investigation.”
Novel strategies
In a comment, Iva Miljkovic, MD, PhD, associate professor, department of epidemiology, University of Pittsburgh, said the investigators used “very rigorous methodology.”
The finding suggesting that lean mass is associated with better cognitive function is “important, as cognitive impairment can become stable rather than progress to a pathological state; and, in some cases, can even be reversed.”
In those cases, “identifying the underlying cause – e.g., low lean mass – can significantly improve cognitive function,” said Dr. Miljkovic, senior author of a study showing muscle fat as a risk factor for cognitive decline.
More research will enable us to “expand our understanding” of the mechanisms involved and determine whether interventions aimed at preventing muscle loss and/or increasing muscle fat may have a beneficial effect on cognitive function,” she said. “This might lead to novel strategies to prevent AD.”
Dr. Daghlas is supported by the British Heart Foundation Centre of Research Excellence at Imperial College, London, and is employed part-time by Novo Nordisk. Dr. Miljkovic reports no relevant financial relationships.
A version of this article first appeared on Medscape.com.