The earsplitting sound of ambulance sirens in New York City is surely hastening the day when I, and many others repeatedly subjected to such noise, will be forced to get hearing aids. I just hope this doesn’t happen before 2021 or so when these devices become available over the counter and are far less expensive and perhaps more effective than they are now.

Now, a growing body of research by Dr Frank R. Lin, director of the Cochlear Center for Hearing and Public Health at the Johns Hopkins Bloomberg School of Public Health, and others is linking untreated hearing loss to several costly ills.

Not only is poor hearing annoying and inconvenient, it is also an unmistakable health hazard, threatening mind, life and limb. Currently, 38.2 million Americans aged 12 or older have hearing loss, a problem that becomes increasingly common and more severe with age. More than half the people in their 70s and more than 80 per cent in their 80s have mild to moderate hearing loss or worse, according to the National Health and Nutrition Examination Survey between 2001 and 2010.

Two huge new studies have demonstrated a clear association between untreated hearing loss and an increased risk of dementia, depression, falls and even cardiovascular diseases. In a significant number of people, the studies indicate, uncorrected hearing loss itself appears to be the cause of the associated health problem.

In one of the studies that covered 1,54,414 adults 50 and older, researchers at Johns Hopkins found that untreated hearing loss increased the risk of dementia by 50 per cent and depression by 40 per cent in just five years. An analysis of the voluminous data by Nicholas S. Reed and colleagues linked untreated hearing loss to more and longer hospitalisations and readmissions and more visits to an emergency room.

About 85 per cent of those with hearing loss are untreated, Lin said. For older adults alone, this increased healthcare costs by 46 per cent over a period of 10 years, the authors reported in JAMA Otolaryngology Head and Neck Surgery.

One of the authors, Jennifer A. Deal, an epidemiologist and gerontologist at the Johns Hopkins Bloomberg School of Public Health, said that while “hearing loss itself is not very expensive, the effect of hearing loss on everything else is expensive”. Unfortunately, people tend to wait too long to get tested and treated with hearing aids, and the longer they wait, the harder it is to treat hearing loss, Lin said. He cited two good clues to when to get your hearing tested: family members or friends say you should, or you notice that you often mishear or don’t know what others are saying.

But even when people are tested and spend thousands to purchase hearing aids, the devices often sit in a drawer. People may complain that the sound quality is poor, too static-y or otherwise annoying, and that the aids merely amplify all sound, making it still hard to hear in a noisy environment. All aids are not created equal, Lin said, and even expensive, properly fitted aids can require multiple adjustments. Some people give up too readily to get the best results.

The new studies give ample cause for taking hearing loss seriously. Consider, for example, the link to dementia. People who can’t hear well often become socially isolated and deprived of stimuli that keep the brain cognitively engaged. As input lessens, so does brain function. There’s also a heavier load on the brain when it’s forced to use too much of its capacity to process sound. Our brains are not designed for multitasking.

With respect to falls, Deal said, hearing loss often goes hand-in-hand with balance issues. “Even when we don’t realise it, we’re using our ears to position ourselves in space,” she explained. Also, when people can’t hear well, they are less aware of sounds around them. They may fall when startled by someone or something that seems to come silently from behind.

Deal said she and her co-authors were surprised to find a link between poor hearing and cardiovascular disease. “It could be that vascular disease is common to both,” she said, but added that social isolation and stress resulting from hearing loss are also play a role.