Genetic analysis of perceived youthfulness reveals differences in how men's and women’s age is assessed

Skin aging is a natural process that occurs over time, but can be accelerated by sun exposure. Measuring skin age in a large population can provide insight into the extent of skin damage from sun exposure and skin cancer risk. Understanding the genetics of skin aging, within and across sexes, could improve our understanding of the genetic drivers of both skin aging and skin cancer. We used UK Biobank data to examine the genetic overlap between perceived youthfulness and traits relevant to actinic photoaging. Our GWAS identified 22 genome-wide significant loci for women and 43 for men. The genetic correlation between perceived youthfulness in men and women was significantly less than unity (rg=0.75, 95% CI=0.69-0.80), suggesting a gene-by-sex interaction. In women, perceived youthfulness was modestly correlated with keratinocyte cancer (rg = -0.19) and skin tanning (rg = 0.18). In men, perceived youthfulness was correlated with male pattern baldness (rg = -0.23). This suggests that the genetic architecture of perceived youthfulness may differ, with genes influencing skin tanning and skin cancer susceptibility driving the difference in women, while genes influencing male pattern baldness and other puberty-related traits drive the difference in men. We recommend future genetic analysis of skin aging include a sex-stratified component.