Skeletal Muscle Function Deficit Longitudinal Associations With Inflammation and Caloric Intake in Elderly. The InCHIANTI Study
Matteo Candeloro, Chiara Candita, Raffaello Pellegrino, Giada Mariano, Ettore Porreca, Giovanni Barassi, Roberto Paganelli, Angelo Di Iorio, Toshiko Tanaka, Luigi FerrucciABSTRACT
Background
The Skeletal Muscle Function Deficit (SMFD) score integrates muscle mass, strength, power and quality into a single construct that evaluates the multidimensional status of muscle health. The aim of the study is to investigate the longitudinal associations of systemic inflammation and caloric intake with SMFD‐score trajectories in older adults from the InCHIANTI study.
Methods
Data were obtained from the InCHIANTI population‐based longitudinal cohort. A total of 1035 community‐dwelling older adults (mean age 74.97 ± 7.39 years; 44.25% men) contributed 3196 repeated observations across four study waves. SMFD‐score (range 0–20) was derived from sex‐specific quintiles of lower‐limb muscle mass, muscle density, grip strength and lower‐limb power; participants unable to perform a test received a score of 0 for that component. Interleukin‐6 (IL‐6) and caloric intake (kcal/day) were assessed at all study waves. Longitudinal associations between time‐varying IL‐6 tertiles, caloric intake tertiles and SMFD‐score trajectories were evaluated using linear mixed‐effects models adjusted for baseline age and sex and time‐varying multimorbidity and body mass index.
Results
Across follow‐up, SMFD‐score declined significantly from 9.60 ± 4.20 at baseline to 7.07 ± 4.00 at the last wave ( p < 0.001), whereas IL‐6 increased from 3.65 ± 2.50 pg/mL to 4.39 ± 3.10 pg/mL ( p < 0.001). Mean caloric intake showed a non‐significant upward trend (1912.83 ± 562.37 to 1976.00 ± 580.54 kcal/day; p = 0.07). In mixed‐effects models, higher IL‐6 levels were associated with accelerated SMFD decline over time (IL‐6 tertile × time interaction β = −0.31 ± 0.02; p < 0.001). Higher caloric intake was associated with higher SMFD‐score and a slower functional decline (caloric intake tertile main effect β = 1.19 ± 0.16; p < 0.001; caloric intake tertile × time interaction β = 0.24 ± 0.03; p < 0.001). In the model including the combined IL‐6 × caloric intake × time interaction was statistically significant (β = 0.14 ± 0.04; p < 0.001), indicating that higher caloric intake partially attenuated the negative longitudinal association between IL‐6 and SMFD‐score.
Conclusions
SMFD‐score captures longitudinal muscle function decline during aging and reflects the opposing influences of inflammation and caloric intake. These findings support the SMFD‐score as a clinically relevant construct for identifying potentially modifiable determinants of muscle health and functional decline in older adults.