Low masseter muscle mass is associated with frailty in community-dwelling older adults: I-Lan Longitudinal Aging...

Sarcopenia, defined as age-related diminution of muscle mass and strength, is a key determinant of frailty status and progression. We investigated the hypothesis that changing masseter muscle structure with advancing age may contribute to the development of frailty.

Study data were excerpted from the I-Lan Longitudinal Aging Study, a research cohort of community-dwelling residents aged ≥53 years from Yilan (I-Lan) County, Taiwan. The study sample comprised 56 subjects classified as frail, 41 pre-frail, and 41 robust, according to Cardiovascular Health Study criteria; all groups were matched by age and sex. Masseter muscle volume was quantified based on T1-weighted magnetic resonance imaging, and adjusted for height to derive the masseter volume index (MVI). Appendicular skeletal muscle mass index (SMI) was determined by dual-energy X-ray absorptiometry, and used to derive the height-adjusted skeletal mass index (SMI). Nutrition status was assessed with the Mini-Nutritional Assessment (MNA) form.

The MVI was significantly smaller in frail versus pre-frail subjects. Among frail individuals, only the MVI was significantly correlated with MNA scores. MVI, but not SMI, was associated with increased risk of being frail versus pre-frail. An MVI cut-off score of 9.5 cm³/m² in males discriminated frail from pre-frail status with acceptable sensitivity and specificity. Low MVI was associated with the frailty criteria of slowness.

MVI is a potential clinical index for evaluating phenotypic frailty. Diminished masseter muscle volume may predispose pre-frail/frail elders to depletion of physical reserves, consequent to its detrimental effect on oral functioning and nutrient intake.