What slows aging the most?

Consistent daily sunscreen use is the most evidence-backed external factor in slowing skin ageing. UV exposure is responsible for up to 80% of visible facial ageing. Beyond sun protection, not smoking, maintaining skin hydration, and using retinoids or antioxidants at night are the next most studied contributors to slower skin ageing.

Photoaging, the ageing caused by UV exposure, accounts for the majority of what we visually associate with older skin: fine lines, loss of elasticity, age spots, and rough texture. A landmark study in the Annals of Internal Medicine found that people who used sunscreen daily showed no detectable increase in skin ageing over a four-and-a-half-year period. Sleep, stress management, and diet contribute to skin health at a cellular level. But if you had to choose one daily habit with the strongest evidence behind it, sunscreen wins.

Sources:
Hughes et al., Annals of Internal Medicine, 2013.