At 100, Ann Stenzel is feisty and sharp, in part because her hearing aids, which she has used for a decade, keep her in touch with the world around her.

She likes to spend her mornings reading the newspaper in the sunny lobby of her seniors residence center, Eskaton Lodge Granite Bay, where she strikes up conversations with fellow residents.

"I don't want to miss anything," said Stenzel. "But half the people here can't hear. What they tell you is, 'Hearing aids? I don't need hearing aids.' It gets to me when they say that, because they do need them.

"They'll say it makes them feel old to get hearing aids. But wearing them makes me feel young."

The incidence of hearing loss, one of the hidden impairments of old age, has doubled in the past three decades. It affects 26.7 million Americans 50 and older, including four out of five people above age 80, and numbers are expected to rise with the aging of baby boomers.

But despite its prevalence among older adults, hearing loss remains largely untreated: Only 14 percent of seniors who need hearing devices actually have them.

As a result, many older adults are unnecessarily missing out on the life that's swirling around them, unheard and unacknowledged.

Researchers say it's possible they're putting their health at risk, too. A recent Johns Hopkins University study suggests that hearing loss can upset fragile seniors' sense of balance, tripling their chances of a fall.

And diminished hearing affects older adults' quality of life. It can lead to early retirement and less independence for people in their 50s and 60s – and for older seniors, inability to hear and communicate can launch them into a downward spiral of isolation and self-neglect.

"If hearing loss is mild, people are still able to be involved in the environment around them and take part in social activities," said Kaiser Permanente South Sacramento Medical Center audiologist Robert Spacagna. "If it's greater, they can't sit in a restaurant and hear separate conversations. They can't communicate. It's frustrating because it's so much work for them.

"Over time, they become isolated and give up their normal activities. They stay in their own little world and forget the other world."

Some research suggests that severe hearing loss later in life goes hand in hand with an older adult's risk of dementia, although experts say more study is required to establish causality, rather than correlation.

"As someone becomes increasingly hearing impaired, it can be difficult separating out the confusion caused by their isolation and inability to hear, on the one hand, and the confusion caused by a brain disorder," said Elizabeth Edgerly, chief program officer of the Alzheimer's Association of Northern California.

"We educate people on the impact of hearing loss and cognition. If information isn't getting in to begin with, the person won't be able to remember it and use it later."

Gradual hearing loss is the most common chronic condition of old age after hypertension and arthritis, says the American Association on Hearing Loss. It has become a normal, almost inevitable part of aging as a result of many decades' worth of exposure to the loud noises of modern life: the screeching and honking of rush-hour traffic, the roar of jet engines, the deafening whir of lawn mowers and power tools.

Medications commonly used in advanced age, including some antibiotics and diuretics, also have been found to cause temporary or permanent hearing loss. So have Viagra and Cialis, according to the U.S. Food and Drug Administration.

But in most cases, age-related hearing loss is easily correctable through the use of properly fitted hearing aids, which these days are tiny digital devices that can be fine-tuned to accommodate different sound environments.

A restaurant, for example, or a movie theater. Or a telephone conversation.

So why do such a small number of hearing-impaired older adults – only one of every seven – actually use hearing aids?

For one thing, the technology can overwhelm older people, who tend to be a few decades removed from the Bluetooth-wearing, earbud-loving generations for whom a hearing aid might be just another high-tech device to put in the ear.

Some seniors are too proud to admit they need assistance with their hearing, experts say – and other seniors, frankly, are too vain to wear hearing aids.

Besides, said 90-year-old Elk Grove resident Opal Murphy: "Hearing is one thing you can get along without, if you have to."

She knows. Up until a few months ago, she lived with diminished hearing. It took her awhile to realize her ears were the problem: For years, she thought people were mumbling.

As many older adults like to tell one another, you don't miss what you don't hear.

"It's really unfortunate," said Senior Center of Elk Grove executive director Pat Beal. "Seniors say, 'I get by.' Or when you talk to them, they just smile and nod and say, 'Uh-huh.'

"It's one more thing going wrong with them as they get older, and it really speaks to them about aging."

But Murphy finally decided she was missing a lot.

"Here at the senior center," she said, "I couldn't hear my friends talking just across the table from me."

So she had her hearing tested. And then she faced the third major reason that older adults hesitate to buy hearing aids: the price tag.

Medicare doesn't routinely cover the cost of hearing aids – which can run from $1,000 to $4,000 per ear – nor do most private medical plans. (Similarly, Medicare covers only prescription eyeglasses after certain cataract surgeries.) Murphy took half her hearing devices' $2,000 cost out of savings and put the rest on a credit card.

"It's an investment," said Jane Rupp, a registered nurse with Eskaton whose father wears hearing aids. "But from the perspective of spouses and families, it makes communicating with your loved ones easier."

In her Granite Bay assisted living center, Ann Stenzel has become a staunch hearing aid advocate, mostly because she remembers how astonished she was when she tried on her first pair and learned how much of life around her she'd been missing.

"I put those things in and said, 'I can hear! I can hear!' " she said. "This hearing aid business, I'm all for it.

"We have a gal here I'm trying to talk into hearing aids. She says she can't afford them. And I tell her, 'Well, find a way. Because your hearing's not going to get better. It's only going to get worse.' "

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