There are two factors that affect the aging of the skin: extrinsic (external) and intrinsic (internal) aging.
Intrinsic aging is biological aging that occurs with the passing of time. Over time, the body experiences a break down in cell to cell communication, causing everything to slow down. From cellular metabolism and cellular turnover to mutations in DNA - our body cannot repair itself like it did when we were younger. Glycation is another concern that affects the body and skin over time. A loss of resources such as collagen, elastin and hyaluronic acid while also triggering fine lines, wrinkles, loss of hydration and firmness.
Extrinsic aging is a result of our daily environment. Daily exposure to UV rays, pollution, poor nutrition, and stress all contribute. Whether this is from a depletion of antioxidants, mutations in our DNA, increased inflammation or external factors- each will contribute in accelerating the aging process.