The Physiological Realities of Aging

Key Insight

Aging involves a complex, systemic degradation of the body's components. For instance, teeth, the hardest substance, wear away, exposing softer layers, while blood supply to roots atrophies and saliva diminishes. Gums inflame and recede, making teeth unstable and elongating their appearance. Experts can estimate a person's age within five years from a single tooth. Challenges like arthritis or tremors hinder dental care, and reduced nerve sensitivity can delay cavity detection. Jaw muscles lose about 40% of their mass, and mandible bones lose around 20%, becoming porous, leading to decreased chewing ability and a shift to softer, often cavity-promoting foods. By age sixty, people in industrialized nations average a one-third tooth loss, and after eighty-five, almost 40% are toothless.

Concurrently, while bones and teeth soften, much of the rest of the body stiffens. Blood vessels, joints, heart muscles and valves, and even lungs accumulate substantial calcium deposits, displaying a bone-like calcium form under a microscope, making major vessels feel 'crunchy' during surgery. Loss of bone density has been found to be a better predictor of death from atherosclerotic disease than cholesterol levels, suggesting calcium redistributes from the skeleton to soft tissues. The heart must generate increased pressure to maintain blood flow through narrowed, stiffened vessels, leading to hypertension in over half of individuals by age sixty-five. The heart muscle thickens, becoming less responsive to exertion, and its peak output steadily decreases from age thirty, resulting in reduced physical endurance.

Muscle mass and power begin to decline around age forty, with individuals losing between a quarter and a half of their muscle weight by age eighty. This decline is evident in the hand, where thenar (thumb) muscles can lose 40% of their mass, making the palm flat rather than bulging. X-rays show arterial calcification and bones losing density at nearly 1% per year from age fifty. The hand's twenty-nine joints are prone to osteoarthritis, causing ragged surfaces, collapsed joint spaces, pain, swelling, reduced wrist motion, and diminished grip. Deterioration of forty-eight named nerve branches, along with loss of mechanoreceptors and motor neurons, impairs touch sensitivity and dexterity, degrading handwriting and making modern devices challenging to use. Brains also shrink, losing almost an inch of gray matter by the seventies, increasing susceptibility to cerebral bleeding. Frontal lobes (judgment, planning) and the hippocampus (memory) are the earliest to shrink, causing memory and multitasking abilities to peak in midlife and then decline, with processing speeds decreasing even before age forty. By eighty-five, 40% of people exhibit textbook dementia due to impaired working memory and judgment. These physiological changes are normal and, though they can be slowed by diet and activity, cannot be stopped.