The rate of energy production in the body cells is gradually lowered so that people tire more easily and are more sensitive to weather changes. Sexual desire and ability lower although they never entirely end for either sex. The capacity to bear children ends in women with menopause, which is the time when the ovaries stop functioning, causing the menstrual cycle to stop. Men retain their reproductive function into the late years. The use of eyeglasses may become necessary, even if they were not necessary earlier in life.
Old people can hear low tones fairly well, but their ability to hear high tones decreases.
The capacity of tissue and bone to repair itself is slowed, as is cellular growth and division. Bones become brittle and skin loses its thickness and elasticity, causing wrinkles. As brain cells die some capacity for memorization and learning is lost. Breathing becomes difficult, and hardening arteries circulation to worsen and blood pressure to rise. Joints lose their mobility and deteriorate from constant wear and pressure.