Aging changes in the senses
Aging changes in the senses are perceptual changes related to growing older.
When you age, the way your senses (taste, smell, touch, vision, and hearing) are able to give you information about the world changes. Your senses become less acute, and you may have trouble distinguishing details.
Sensory changes can have a tremendous impact on your lifestyle. You may have problems with communication, enjoyment of activities, and social interactions. Sensory changes can contribute to a sense of isolation.
All of the senses receive information of some type from the environment (light, sound vibrations, and so on). This is converted to a nerve impulse and carried to the brain, where it is interpreted into a meaningful sensation.
Everyone requires a certain minimum amount of stimulation before a sensation is perceived. This minimum level is called the threshold. Aging increases this threshold, so the amount of sensory input needed to be aware of the sensation becomes greater. Changes in the body part related to the sensation account for most of the other sensation changes.
Hearing and vision changes are the most dramatic, but all senses can be affected by aging. Fortunately, many of the aging changes in the senses can be compensated for with equipment such as glasses and hearing aids or by minor changes in lifestyle.
Your ears have two jobs. One is hearing and the other is maintaining balance. Hearing occurs after vibrations cross the eardrum to the inner ear. They are changed into nerve impulses and carried to the brain by the auditory nerve.
Balance (equilibrium) is controlled in a portion of the inner ear. Fluid and small hairs in the semicircular canal (labyrinth) stimulate the nerve that helps the brain maintain balance.
As you age, your ear structures deteriorate. The eardrum often thickens and the bones of the middle ear and other structures are affected. It often becomes increasingly difficult to maintain balance.
Hearing may decline, especially that of high-frequency sounds, particularly in people who have been exposed to a lot of noise when younger. This age-related hearing loss is called presbycusis. Some hearing loss is almost inevitable. It is estimated that 30% of all people over 65 have significant hearing impairment.
The sharpness (acuity) of hearing may decline slightly beginning about age 50, possibly caused by changes in the auditory nerve. In addition, the brain may have a slightly decreased ability to process or translate sounds into meaningful information. Impacted ear wax is another cause of trouble hearing and is more common with increasing age. Impacted ear wax may be removed in your doctor's office.
Sensorineural hearing loss involves damage to the inner ear, auditory nerve, or the brain. This type of hearing loss may or may not respond to treatment, but function can be helped by hearing aids.
Conductive hearing loss occurs when sound has problems getting through the outer and middle ear to the inner ear. Surgery or a hearing aid may be helpful for this type of hearing loss, depending on the specific cause.
Persistent, abnormal ear noise (tinnitus) is another fairly common hearing problem, especially for older adults. It is usually a result of mild hearing loss.
Vision occurs when light is processed by your eye and interpreted by your brain. Light passes through the transparent eye surface (cornea).
Your pupil is an opening to the inside of the eye. It becomes larger or smaller to control the amount of light that enters your eye. The colored portion (iris) is a muscle that controls the pupil size.
After light passes through your pupil, it reaches the lens. The lens focuses light on your retina (the back of the eye). Your retina converts light energy into a nerve impulse that is carried to the brain and interpreted.
Some age-related eye changes may begin as early as your 30s. Aging eyes produce less tears. Dry eyes can be quite uncomfortable. Many people find relief by using eyedrops or artificial tears solutions.
All of the eye structures change with aging. The cornea becomes less sensitive, so injuries may not be noticed. By the time you turn 60, your pupils decrease to about one-third of the size they were when you were 20.
The pupil may also react more slowly in response to darkness or bright light. The lens becomes yellowed, less flexible, and slightly cloudy. The fat pads supporting the eye decrease and the eye sinks back into the socket. The eye muscles become less able to fully rotate the eye.
As you age, the sharpness of your vision (visual acuity) may gradually decline. Glasses or contact lenses may help correct age-related vision changes. You may eventually need bifocals.
Almost everyone older than 55 needs glasses at least part of the time. However, the amount of change is not universal. Only 15% to 20% of older people have bad enough vision to impair driving ability, and only 5% become unable to read. The most common problem is difficulty focusing the eyes on something close (a condition called presbyopia).
You may be less able to tolerate glare, and you may find that you have more trouble adapting to darkness or bright light. Many older people find that although their vision is good enough to drive during the day, they must give up night driving because of problems with glare, brightness, and darkness. Significant difficulty with night driving may be the first sign of a cataract (a clouding of the eye lens).
Indoor glare, such as glare from a shiny floor in a sunlit room, can also make it difficult to get around inside.
For people of all ages, it is harder to distinguish blues and greens than it is to distinguish reds and yellows. This becomes even more pronounced with aging. As your age increases, using warm contrasting colors (yellow, orange, and red) in your home can improve your ability to tell where things are and makes it easier to perform daily activities.
Many older people find that keeping a red light on in darkened rooms (such as the hallway or bathroom) makes it easier to see than using a "regular" night light. Red light produces less glare than a regular incandescent bulb.
With aging, the fluid inside your eye may change. Small particles can create "floaters" in your vision. Although annoying, floaters usually do not indicate a dangerous condition and usually do not reduce vision. If you suddenly develop floaters or have a rapid increase in the number of them, you should have your eyes checked by a professional.
When your eyes are examined, you may not be able to move your eye in all directions. Your upward gaze may be limited. The area in which objects can be seen (visual field) gets smaller.
Reduced peripheral vision is common and can limit social interaction and activity. Older people may not communicate with people sitting next to them because they cannot see them well -- or perhaps at all. Food and drinks may be spilled. Driving can become dangerous.
TASTE AND SMELL
The senses of taste and smell interact closely, helping you appreciate food. Most taste really comes from odors. The sense of smell begins at nerve receptors high in the membranes of the nose.
You have approximately 9,000 taste buds. Your taste buds are primarily responsible for sensing sweet, salty, sour, and bitter tastes.
Smell (and to a lesser extent, taste) also play a role in both safety and enjoyment. We detect certain dangers, such as spoiled food, noxious gases, and smoke with taste and smell. A delicious meal or pleasant aroma can improve social interaction and enjoyment of life.
The number of taste buds decreases beginning at about age 40 to 50 in women and at 50 to 60 in men. Each remaining taste bud also begins to atrophy (lose mass). The sensitivity to the four taste sensations does not seem to decrease until after age 60, if at all. If taste sensation is lost, usually salty and sweet tastes are lost first, with bitter and sour tastes lasting slightly longer.
Additionally, your mouth produces less saliva as you age. This causes dry mouth, which can make swallowing more difficult. It also makes digestion slightly less efficient and can increase dental problems.
The sense of smell may diminish, especially after age 70. This may be related to loss of nerve endings in the nose.
Studies about the cause of decreased sense of taste and smell with aging have conflicting results. Some studies have indicated that normal aging by itself produces very little change in taste and smell. Rather, changes may be related to diseases, smoking, and environmental exposures over a lifetime.
Regardless of the cause, decreased taste and smell can lessen your interest and enjoyment in eating. Some people become less aware of personal hygiene when the sense of smell is decreased. Enjoyment of your environment may be diminished.
Sometimes changes in the way food is prepared, such as a change in the spices used, may help.
For some people, there is an increased risk of asphyxia because they cannot detect the odor of natural gas from the stove, furnace or other appliance. A visual gas detector that changes appearance when natural gas is present may be helpful.
TOUCH, VIBRATION, AND PAIN
The sense of touch also includes awareness of vibrations, pain, and your body position. The skin, muscles, tendons, joints, and internal organs have receptors that detect touch, temperature, or pain.
Your brain interprets the type and amount of touch sensation. It also interprets the sensation as pleasant (such as being comfortably warm), unpleasant (such as being very hot) or neutral (such as being aware that you are touching something).
Medications, brain surgery, problems in the brain, confusion, and nerve damage from trauma or chronic diseases such as diabetes can change this interpretation without changing awareness of the sensation. For example, you may feel and recognize a painful sensation, but it does not bother you.
Some of the receptors give the brain information about the position and condition of internal organs. Even though you may not be consciously aware of this information, it helps to identify changes (for example, the pain of appendicitis).
Many studies have shown that with aging, you may have reduced or changed sensations of pain, vibration, cold, heat, pressure, and touch. It is hard to tell whether these changes are related to aging itself or to the disorders that occur more often in the elderly.
It may be that some of the normal changes of aging are caused by decreased blood flow to the touch receptors or to the brain and spinal cord. Minor dietary deficiencies, such as decreased vitamin B1 (thiamine) levels, may also be a cause of changes.
Regardless of the cause, many people experience changes in the touch-related sensations as they age. You may find it harder, for example, to tell the difference between cool and cold. Decreased temperature sensitivity increases the risk of injuries such as frostbite, hypothermia, and burns.
Reduced ability to detect vibration, touch, and pressure increases the risk of injuries, including pressure ulcers. After age 50, many people have reduced sensitivity to pain. You may develop problems with walking because of reduced ability to perceive where your body is in relation to the floor. This increase your risk of falling, a common problem for older people.
Fine touch may decrease. However, some people develop an increased sensitivity to light touch because of thinner skin (especially people older than 70).
To increase safety, make allowances for changes in touch-related sensations:
- Limit the maximum water temperature in your house (there is an adjustment on the water heater) to reduce the risk of burns.
- Look at the thermometer to decide how to dress rather than waiting until you feel overheated or chilled.
- Inspect your skin (especially your feet) for injuries, and if you find an injury, treat it. Don't assume that just because an area is not painful, the injury is not significant.
Caprio TV, Williams TF. Comprehensive geriatric assessment. In: Duthie EH, Katz PR, Malone ML, eds. Practice of Geriatrics. 4th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 4.
Hile ES, Studenski SA. Instability and falls. In: Duthie EH, Katz PR, Malone ML, eds. Practice of Geriatrics. 4th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 17.
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc