Anatomically the brain shrinks in size with advancing age; after age 60 years, its size declines by 5 to 10%. The decrease in size is caused primarily by a decrease in brain tissue in the cerebral cortex. Novel adjustments made by the brain include the formation of new connections between remaining neurons. Aging is associated with a progressive decline in the synthesis of neurotransmitters and a decline in their corresponding receptors. A major functional change is slower reaction times, which may be the result of a slower nerve conduction or transsynaptic speed.

The farsightedness of aging is caused by the diminished ability of the lens to focus on nearby objects because of its thickening and stiffening. There is reduced ability to distinguish colors, particularly blue, owing to yellowing of the lens. Overall transmission of light through the lens may decline by 50 to 65% between ages 25 to 60 years; as a result, individuals require more ambient light. Older individuals experience more glare because light scatters through the thickened lens. Older individuals also notice more floaters as the vitreous jelly becomes slightly more liquefied and mobile with advancing age. Tear production is decreased, leading to a sense of grittiness in the older eye. Overall visual acuity tends to decrease with age, and by age 65 years, 40% of men and 60% of women have a visual acuity of 20/70 or worse.

Approximately 25% of individuals older than age 65 experience hearing loss with age, with men affected more than women. The degeneration of neural transmission from the ear to the brain results in difficulty identifying a voice or understanding a spoken message when there is background noise. Presbycusis results in high-frequency sound loss and more difficulty distinguishing high-pitched consonants and voices compared with lower pitched vowels and sounds.

Sleep patterns change with advancing age. Functionally, older adults are more wakeful during the night and spend much more time in bed. The pattern of sleep characteristically changes from the fairly regular stepwise patterns of childhood and young adulthood to a more fragmented pattern, with frequent awakenings in late life.