Merck Manual

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How the Body Ages: Some Normal Changes

How the Body Ages: Some Normal Changes

What Happens?


Mental function

Difficulty remembering or coming up with the right word

Difficulty concentrating

Difficulty learning new material

The nerve cells in the brain release different amounts of some chemical messengers (which send impulses from cell to cell), and the number of receptors on nerve cells may decrease. Thus, the brain does not send or process impulses as well or as quickly.

Physical activity

Unsteadiness or loss of balance

Structures in the inner ear that help with balance stiffen and deteriorate slightly.

The part of the brain that controls balance (cerebellum) may degenerate.

Dizziness or light-headedness when standing

The heart does not pump enough blood to the head because the heart is less able to respond to changes in position.

The nervous system signals the heart to increase blood flow less effectively.

The blood vessels do not constrict enough to maintain normal blood pressure when a person stands.

Loss of muscle strength

The number and size of muscle fibers decrease.

The body produces less growth hormone and (in men) less testosterone, which help maintain muscles.

Difficulty moving

Less flexibility

Less joint fluid is produced.

The cartilage between bones in joints becomes stiffer and may erode.

Tendons and ligaments become stiffer and weaker.

Muscle tissue is lost, replaced by fatty or fibrous tissue, decreasing strength and making muscles stiffer.

Difficulty exercising strenuously

The heart cannot keep up with the demand for more blood during exercise. It cannot speed up as quickly or pump as fast as it used to, partly because the heart and blood vessels become stiffer and less elastic. Also, the heart does not respond as quickly or as well to chemical messengers that normally stimulate it to speed up.

The lungs cannot keep up with the demand for oxygen during exercise. Less air is taken in with each breath, and the lungs do not absorb as much oxygen.

The senses

Need for reading glasses

The lens of the eye stiffens, making focusing on close objects more difficult.

Difficulty seeing in dim light

The retina of the eye becomes less sensitive to light.

The lens of the eye becomes less transparent.

Difficulty adjusting to changes in light levels

The pupils react more slowly to changes in light.

Darkened areas in the lens of the eye increase glare.

The number of cells that produce fluids to lubricate the eyes decreases.

The tear glands produce fewer tears.

Difficulty understanding words

Age-related hearing loss (presbycusis) develops, which often affects mainly high frequencies (which include consonants—the sounds that help people identify words).

Age-related hearing loss (presbycusis) develops.

Earwax accumulates.

Loss of taste

Taste buds become less sensitive.

People detect odors less well because the lining of the nose becomes thinner and drier and the nerve endings in the nose deteriorate.

Less saliva is produced.

Eating problems

The mouth is dry.

The muscles involved in swallowing weaken, and coordination is impaired.

People may not chew food enough because teeth are missing or dentures do not fit well. Then, chunks of food are too large to swallow.

The bones at the top of the spine change, tipping the head forward and thus compressing the throat.

Disinterest in eating

Taste decreases, making food less appetizing.

Smell decreases, making food less appetizing.

The mouth is dry, leading to loss of taste.

Chewing may be difficult because teeth are missing, jaw muscles are weak, or dentures do not fit well.

Swallowing is difficult.

Skin and hair


More tears in the skin

The fat layer under the skin, which acts as a cushion, thins.

The body produces less collagen and elastin, which make the skin tough and elastic.

Glands in the skin produce less oil.

Bruises and broken blood vessels

Blood vessels in the skin become more fragile.

Slow healing of wounds

The number of blood vessels in the skin decreases.

Cells responsible for healing wounds act more slowly and decrease in number.

Difficulty adjusting to changes in temperature

The fat layer under the skin, which helps conserve body heat, thins.

The number of sweat glands decrease, and the sweat glands produce less sweat. Sweat helps cool the body.

The number of blood vessels decreases, and blood flow in the deep layers of the skin decreases. As a result, the body cannot remove heat from the body as well.

Decreased sensation and sensitivity to pain

The number of nerve endings in the skin decreases.

Gray or white hair

The hair follicles produce less pigment (melanin).

Thinning or loss of hair

Hairs, which must be replaced periodically, grow more slowly, and some hair follicles stop producing new hair.

Sexual function

Dryness of the vagina

Less estrogen is produced.

Erections that do not last as long, are less rigid, or take more time

Less testosterone is produced.

Blood flow to the penis decreases.