How do the heart, lungs, kidneys, and brain change with age?

Aging is a complex physiological process characterized by a gradual decline in the reserve capacities of various organ systems, often exacerbated by a loss of cells and reduced cellular performance.1

Cardiovascular System

The heart experiences a loss of muscle fibers, which are replaced by fat and connective tissue, alongside the accumulation of "age pigment" (lipofuscin). While resting heart rate remains stable, the heart's maximum output and power diminish due to reduced enzyme activity. Blood vessels lose elasticity as collagen fibers stiffen, often leading to increased blood pressure.2

Respiratory System

Lung function declines as the chest cage becomes stiffer and respiratory muscles weaken. The lungs lose elastic properties, and the total volume of air that can be expelled decreases. While oxygen transfer remains generally adequate at rest, it becomes impaired during strenuous exercise.3

Kidneys

The kidneys show a reduced ability to concentrate urine, requiring more water to excrete waste. This is linked to a loss of nephrons and decreased blood flow to the organ.4

Brain

Structural changes are generally subtle, involving a slight loss of neurons. Many observed cognitive impairments are often attributed to disease-related factors, such as reduced blood supply, rather than aging itself.5