As we age, both the size and strength of our muscle declines from disuse, resulting in an increase in functional limitations. It would make sense that these two factors play a role in increasing risk of mortality due to their effects on overall function, but muscle strength may have a more association with mortality than you’d expect. In a recent study published in the Journal of Gerontology by Newman et al., the ratio of muscle size to strength was examined in relationship to mortality along with a host of other factors.
This study included 3075 healthy men and women aged 70-79 surveyed every 6 months with total mortality being assessed over a span of 6 years. Two main variables were of importance in this study – measurements of muscle mass and body composition which were taken via imaging (CT, DXA), and muscle strength which was measured via grip strength and knee extension (quadriceps) strength. The study also looked at other variables that may affect the strength-mortality association including age, race, physical activity, chronic conditions, and smoking.
What the study found, is that low muscle strength (grip and quadriceps) alone can, in fact, be a predictor of mortality in both men and women. Measurements of muscle mass did not play a role in this relationship and even when accounting for variables such as chronic illness or physical inactivity, this association between strength and mortality can still be seen. Future research is needed to uncover the underlying cause for this strength-mortality association, but until then perhaps we need to be paying closer attention to grandma and grandpa’s handshake!