In the first study to look at how all five of our senses—hearing, sight, smell, taste, and touch—decline as we age, researchers at the University of Chicago have turned up some surprising new facts. What’s more, the study authors suggest that if you have one or two sensory impairments, such as hearing loss, vision loss, or both, you’re more likely to have other—often unrecognized—sensory deficits.
The researchers sifted through data from about 3,000 participants in the NORC (National Opinion Research Center) survey of older Americans—ages 57 to 85—looking for evidence of decline in any of the five senses. They found that 94 percent of the group had at least one sensory deficit. Thirty-eight percent had deficits in two senses, and 28 percent— more than one in four people—were experiencing difficulties with three, four, or all five senses.
Can one loss beget another?
Most of us over 50 acknowledge that our vision and hearing aren’t as sharp as they once were. But other senses often experience an even sharper decline, the study suggests. The researchers found that 74 percent of the participants had significantly lost some of their sense of taste. Two-thirds of the participants scored below normal on tests of touch. The sense of smell, which is linked to taste, also declined in about a quarter of people.
Perhaps the most intriguing finding from the new research, published in the Journal of the American Geriatrics Society in February 2016, is that sensory losses tend to cluster together in individuals. “What that tells us is that there seems to be a shared underlying process at work,” says William Dale, M.D., Ph.D., associate professor of medicine and section chief of Geriatrics & Palliative Medicine at the University of Chicago Medicine, one of the authors of the new study. Exactly what that process is remains speculative.
“It may be the result of an overall decline in the sensory nervous system, which relays information to the brain from all five senses,” says Dale. “But there may also be environmental factors.” Case in point: The research found that people living in areas with higher levels of pollution were at greater risk of global sensory impairment.
Other key findings included:
- Men were more likely than women to show signs of global sensory loss—except for corrected vision, in which women fared worse.
- Overall, black and Hispanic participants had more sensory dysfunction than white subjects, with one exception, hearing loss, which was similar in all participants regardless of race or ethnicity.
- Hispanic subjects scored better than black and white participants when it came to retaining a sense of taste.
- As could be expected, sensory loss was heightened in older participants—but it was even higher than anticipated, with 94 percent having at least one impairment.
Previous research has shown that sensory decline is associated with poorer health and lower life expectancy. There’s a strong link between loss of sense of smell, for example, and the development of dementia. In a 2014 study published in PLOS ONE, University of Chicago researchers found that a declining sense of smell could effectively predict people who are likely to die over the next five years.
Some sensory loss is expected with age, of course, but it’s important to be alert to trouble and tell your doctor about any changes in your senses so any impairment can be managed or corrected. Your doctor can also rule out any underlying condition, such as diabetes, that may be causing the change. Medications can cause some sensory loss, too, so the fix may be as simple as changing a prescription.
A closer look at the five senses
The sensory system is made up of a vast array of detectors—in the skin and internal organs, the eyes, the ears, the taste buds, and the olfactory center of the nose—that receive information from the world around us and send signals to the brain. With age, all five senses begin to change. Here’s a snapshot of how and why:
1. Vision. The researchers found that 80.3 percent of participants had good vision, 13.6 percent had fair vision, and 6.1 percent were rated poor. (Vision corrected with glasses was consider “good.”)
Aging affects the eyes in many ways. By the time we turn 60, our pupils—the opening that controls the amount of light coming into our eyes—have decreased to about one-third the size they were at age 20. The lens that covers the eye may also become slightly cloudy and stiffer, making it hard to focus.
The most common age-related eye problem, presbyopia (farsightedness), occurs when eye muscles aren’t strong enough to adjust a stiffening lens to allow us to focus up close, such as when reading small print. Other age-related vision problems include macular degeneration (vision loss in the center of the retina) and glaucoma (a rise in fluid pressure inside the eye).
2. Hearing. About 18 percent of the participants in the study had only fair or poor hearing. Age-related hearing loss, called presbycusis, usually affects the ability to hear high-frequency sounds. Unfortunately, those frequencies are important to understanding speech—especially consonant sounds like “t” and “d”—so that people with hearing loss often struggle to understand conversations.
Another common hearing problem in older adults is tinnitus, or ringing in the ears. Additionally, structures in the inner ear, made up of fluid and small hairs, stimulate the auditory nerve, signaling the brain about our position and balance. With age, the sense of balance can also decline, increasing the risk of falls and accidents.
3. Touch. Less than a third of participants were rated as having a normal sense of touch; the rest were either fair or poor. The sense of touch depends on exquisitely sensitive receptors not only in our skin but also in muscles, tendons, joints, and even internal organs. These receptors convey information to the brain about everything from the position of our legs and arms to whether something is hot, cold, rough, or smooth. Health conditions, such as [diabetes] [https://www.healthafter50.com/diabetes/article/what-is-diabetes] or impaired blood flow to nerve endings, and deficiencies in nutrients, such as vitamin B12, can diminish one’s sense of touch.
4. and 5. Smell and taste. The senses of smell and taste work together. If a cold impairs your sense of smell, for example, you may temporarily lose some sense of taste. More than two-thirds of the participants scored only fair or poor on both senses.
A sense of smell and taste may decline for a variety of different reasons. With age, the number of our taste buds declines and those that remain shrink. A sense of taste can also decline when saliva production diminishes. The loss of mucus in the nasal passages, which normally traps odor molecules in the nose long enough for nerve cells to detect them, may be one reason the sense of smell falters. Another may be a loss of nerve endings in the nose.
Whatever the cause, a loss of smell and taste can be hazardous to your health. Being unable to notice when food has spoiled can increase the risk of food poisoning, for example. Loss of taste can compromise your appetite, which can lead to malnutrition and unwanted weight loss. Paradoxically, it can also pose the opposite danger: To compensate for a lack of taste, some people eat richer and richer foods, which can lead to becoming overweight or obese.
Being alert to signs of impairment in the five senses may be important for another crucial reason. “We’re beginning to suspect that a loss of sensory input may affect the brain itself, raising the risk of cognitive problems down the road,” Dale says. “A healthy brain may depend on keeping all those sensory connections as strong as possible.”
For more about sensory impairment, see How to Cope When You Can’t Hear.