Nutrient Cycling

Hair loss is more common in old age due to a combination of factors, including reduction in blood supply, changes in hormone levels, and the aging of hair follicles. As people age, the blood circulation to the scalp can decrease, affecting the health and nourishment of hair follicles. Additionally, hormonal changes, such as a decrease in estrogen and progesterone in women and changes in androgen levels in both sexes, can contribute to hair thinning and loss. Furthermore, the aging process can cause hair follicles to become less active and result in slower hair growth, leading to increased hair loss.

So, the correct option is (A): Reduction of blood supply