Difference in muscle quality over the adult life span and biological correlates in the Baltimore Longitudinal Study of Aging.
OBJECTIVE
To examine differences in a proxy measure of muscle quality across the adult life span and explore potential mechanisms of muscle quality change through identification of cross-sectional correlates of muscle quality.


METHODS
Cross-sectional study.


METHODS
Baltimore Longitudinal Study of Aging.


METHODS
Seven hundred eighty-six individuals with a mean age of 66.3 (range 26-96) (N = 786). A sensitivity analysis was conducted in a subset of participants matched according to sex, muscle mass, and body size.


METHODS
Muscle quality was operationalized as the ratio of knee-extension strength (isokinetic dynamometry) to thigh muscle cross-sectional area (computed tomography). Differences in muscle strength, muscle area, and muscle quality ratio with age were evaluated, and the association between the muscle quality ratio and measures reflecting domains of cognitive function, motor control, peripheral nerve function, adiposity, glucose homeostasis, and inflammation were assessed through multivariate regression analyses.


RESULTS
A linear relationship between age and muscle quality ratio was observed, suggesting a gradual decline in muscle quality over the adult life course. Associations were observed between muscle quality ratio and measures of adiposity, as well as peroneal nerve motor conduction velocity, finger tapping speed, and memory performance (P < .01). The association between muscle quality ratio and nerve conduction velocity was maintained after adjustment for anthropometric measurements (P < .05).


CONCLUSIONS
Muscle quality declines progressively with age over the adult life span and is affected by obesity and neurological factors. Studies are needed to clarify the mechanisms of these associations and their implications for functional outcomes.
Longitudinal Studies Section, Translational Gerontology Branch, Baltimore, Maryland.
Ann Zenobia
AZ
Moore
Giorgio
G
Caturegli
E Jeffrey
EJ
Metter
Sokratis
S
Makrogiannis
Susan M
SM
Resnick
Tamara B
TB
Harris
Luigi
L
Ferrucci
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D015142:Baltimore; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D015577:Geriatric Assessment / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging / Q000502:physiology*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
muscle area; muscle quality; muscle strength