Most people, as they age, gradually lose their hearing. There are a number of reasons for this. the muscles gradually become stiffer all over, including in the ears. This usually erodes hearing near the top of the pitch range. Additionally, most people are exposed to loud noises—music, trains, highway traffic, even conversation—which can gradually diminish hearing; over the decades, it adds up. While total deafness isn’t common, older people do tend to hear less well than younger people do. In many cases, there is a genetic component to hearing loss as well. Some illnesses (including some that can be prevented by vaccination), medications, or chemical exposure can also cause deafness or diminished hearing ability.
Interestingly, not all noise damages hearing the same way. Research now shows that the time of day at which noise exposure occurs has a bearing on how it affects the ability to hear. It turns out that noise exposure at night results in a greater degree of permanent hearing loss than exposure during the day. Damage to hearing sustained during daytime heals more thoroughly than at night.
A surprising danger of hearing loss is that as a person’s hearing starts to g, their brain becomes smaller. Some brain shrinkage is a normal part of aging, though the effect is not always significant. However, a recent study found that for people with impaired hearing—particularly if left untreated—this loss of brain volume is accelerated. Some of this shrinkage is in the auditory processing regions of the brain. According to MRI scans, however, some of the accelerated shrinkage takes place in the parts of the brain where memory and cognition are located, which makes it a dementia danger.
Another effect of hearing loss on the brain involves mood. Hearing loss—though not total deafness—was associated in a study with higher rates of depression. The correlation was stronger in women than in men. Researchers suspect, however, the hearing loss is not a cause of depression; rather, people who live alone, heavy drinkers, and people with a relatively low educational level were more likely both to have depression and to have suffered some hearing loss.