What role does ACTN3 play in Langlebigkeit?

ACTN3 encodes alpha-actinin-3, a protein in fast-twitch muscle fibers. The R577X variant (rs1815739) causes a common deficiency. While strongly linked to sprint and power performance, its role in longevity is indirect and speculative. Some observational studies suggest that ACTN3 deficiency may influence age-related muscle loss (sarcopenia) because slow-twitch fibers are metabolically more efficient. However, large longitudinal studies directly linking ACTN3 to lifespan are lacking. Evidence is mixed: strong for athletic traits, weak for longevity. Population-specific effects and confounding by lifestyle and other genes further limit conclusions. A consumer DNA test alone cannot predict longevity based on this variant.