Genetic and environmental effects on isometric muscle strength and leg extensor power followed up for three years among older female twins

Abstract

The purpose of this study was to examine changes in the contribution of genetic and environmental effects to isometric knee extensor strength and leg extensor power among 63- to 76-year-old female twins over a 3-yr follow-up. At baseline in 2000 the sample comprised 206 monozygotic (MZ) and 228 dizygotic (DZ) twin individuals, and at follow-up in 2003 the sample comprised 149 MZ and 164 DZ twin individuals. Genetic modeling showed that genetic effects explained 58% (95% CI: 46-68%) of the variance in muscle strength at baseline and 56% (95% CI: 41-68%) at follow-up, with no occasion-specific genetic effect. Nonshared environmental effects accounted for 42% (95% CI: 32-54%) of the variation at baseline and 15% (95% CI: 7-26%) at follow-up. In addition, new nonshared environmental effects explained the remaining variance, 29% (95% CI: 22-37%) of muscle strength at follow-up. For muscle power, the same genetic effects accounted for 67% (95% CI: 57-74%) of the variation at baseline and 48% (95% CI: 34-61%) at follow-up. Nonshared environmental effects in common at both measurement points explained 33% (95% CI: 25-43%) of the total variation at baseline and 11% (95% CI: 5-21%) at follow-up. The remaining variance of muscle power at follow-up was accounted for by time-specific environmental effects. Results indicated that the contribution of genetic effects to isometric muscle strength was stable, whereas for leg extensor power the proportion of genetic effects decreased during the follow-up. We observed new specific environmental effects underlying follow-up muscle strength and power, which effects could be due to the onset of new disease processes or changes in lifestyle.

Genetic aspects of skeletal muscle strength and mass with relevance to sarcopenia

“…Even the change in muscle strength with advancing age has been found to be heritable, 44,45 though some studies indicate that the contribution of environmental factors increases at older ages. 42,46 Overall, genetic variation explains a significant fraction of the inter-individual variability in skeletal muscle phenotypes, including muscle traits in older individuals. Despite strong evidence for a heritable component to muscle phenotypes, the genetic underpinnings of this heritability is only beginning to be known.…”

“…47 -51 Only one linkage study has targeted older individuals in particular. Tiainen et al 42 examined 397 microsatellite markers in 94 female dizygotic twin pairs aged 66 -75 years from the Finnish Twin Study on Aging. Significant linkages were reported for knee extensor isometric strength, leg extensor power and calf muscle cross-sectional area.…”

Genes and the ageing muscle: a review on genetic association studies

“…Some data are also available on the heritability of muscle phenotypes in the lower extremities of old people. In research conducted on monozygotic and dizygotic female Finnish twin pairs aged 63-76 years, Tiainen and colleagues found that genetic effects accounted for 20-30% of the variance in handgrip strength, leg extensor power and maximal walking speed (Tiainen et al 2004(Tiainen et al , 2005(Tiainen et al , 2008(Tiainen et al , 2009.…”

Cross-national differences in grip strength among 50+ year-old Europeans: results from the SHARE study

“…Recently, Kuh et al (2002) demonstrated that birth weight, prepubertal height gain, pubertal growth and early infant motor development were associated with midlife grip strength, indicating a beneficial role of early childhood growth. Nutritional factors in early life may thus be in involved, but also genetic factors may play a role as twin studies have shown a substantial genetic component to muscle strength (Frederiksen et al 2002;Tiainen et al 2004Tiainen et al , 2009.…”