The basal metabolism, or 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 decline although they need never entirely end for either sex. Hearing changes also come with greater age. Older people hear low tones fairly well, but their ability to perceive the high tones declines. The capacity of tissue and bone to repair itself is slowed, as is cellular growth and division.
Bones are more brittle.
Skin becomes drier and loses some of its elasticity. Artificial teeth may become necessary. Much of the disability and discomfort that used to be considered a part of normal aging can now be delayed with proper medical care and health habits. No disease is caused by old age, but the expected changes that occur with aging increase the possibility that illness will occur. For example, the cardiovascular system undergoes many structural and functional changes that predispose a person to some pathological conditions.