Is ACTN3 useful for skin aging?

The ACTN3 gene variant (R577X) is well-studied for muscle fiber composition – the RR genotype is associated with sprint and power performance. However, there is no robust scientific evidence linking ACTN3 to skin aging. The few studies that explore a connection are mechanistic or speculative (e.g., possible effects on collagen metabolism or inflammation). Effect sizes are very small, and clinical translation is absent. Many direct-to-consumer tests market ACTN3 as a 'fitness and anti-aging gene,' which is not supported by evidence. Skin aging is driven by UV exposure, lifestyle, hormones, and other genetic factors (e.g., MC1R, COL1A1), not ACTN3. Testing ACTN3 for skin aging is not useful and may mislead consumers. Evidence: mechanistic/speculative.