UC Davis

Background

Falls in the older population are a major public health concern. While many physiological and environmental factors have been associated with fall risk, muscle mitochondrial energetics has not yet been investigated.

Methods

In this analysis, 835 Study of Muscle, Mobility and Aging (SOMMA) participants aged 70-94 were surveyed for number of falls (total), recurrent falls (2+), and fall-related injuries over the past 12 months at baseline and again after one year. Skeletal muscle energetics were assessed at baseline in vivo using 31P Magnetic Resonance Spectroscopy (MRS) after an acute bout of exercise (ATPmax) and ex vivo by High Resolution Respirometry (HRR) of permeabilized muscle fibers from the vastus lateralis (MaxOXPHOS).

Results

At least one fall was reported in 28.7% of SOMMA participants in the first year of the study, with 12% of older adults reporting recurrent falls (2+). Individuals who experienced recurrent falls had a slower 400m walk gait speed (1.0 ± 0.2 vs. 1.1 ± 0.2, p<.001), reported fewer alcoholic drinks per week in the past year (2.4 ± 4.3 vs. 2.8 ± 4.4, p= 0.054), and took a significantly greater number of medication in the 30 days before their baseline visit (5.6 ± 4.4 vs. 4.2 ± 3.4, p<0.05). A history of falls was reported in 63% of individuals who experienced recurrent falls in the first year of the study compared to 22.8% who experienced one or fewer falls. MaxOXPHOS was significantly lower in those who reported recurrent falls (p=0.008) compared to those with one or fewer falls, but there was no significant difference in ATPmax (p=0.369). Neither muscle energetics measure was significantly associated with total number of falls or injurious falls, but recurrent falls were significantly higher with lower MaxOXPHOS (RR=1.33, 95% CI= 1.02-1.73, p=0.033). However, covariates accounted for the increased risk.

Conclusions

Mitochondrial energetics were largely unrelated to fall risk in older adults when accounting for variables, suggesting that the complex etiology of falls may not be related to a single "hallmark of aging" biological pathway.