Can ACTN3 help with longevity?

Yes, the ACTN3 gene variant (R577X, rs1815739) is well-studied for its influence on athletic performance. The R allele is associated with sprint/power performance, while the X allele (null) is linked to endurance. Evidence is human-strong from multiple meta-analyses and cohort studies. However, the effect is moderate and interacts with training, diet, and other genetic factors. Consumer DNA tests can report this variant, but it should not be used as a sole predictor. Regarding the original seed question about longevity: there is no strong evidence that ACTN3 directly affects lifespan. The gene's role is primarily in muscle fiber composition and athletic traits. Caveat: population-specific effects exist; the variant is common (e.g., ~18% X/X in Europeans).