Which of the following is a sign of skin aging?

Reduced hydration is a significant sign of skin aging. As individuals age, the skin's ability to retain moisture diminishes due to several factors, including decreased oil production, reduced natural moisturizing factors, and changes in skin structure. This loss of hydration can lead to dryness, flakiness, and the appearance of fine lines and wrinkles, which are characteristic of aging skin.

In contrast, increased elasticity, improved turgor, and enhanced barrier function are generally associated with healthier or younger skin. Increased elasticity indicates that the skin can stretch and bounce back more easily, while improved turgor reflects the skin's firmness and ability to return to its original shape after being stretched. Enhanced barrier function refers to the skin's ability to protect against environmental factors and retain moisture, which tends to decline with age. Therefore, reduced hydration stands out as a clear indicator of skin aging.