Resource: Moriussaq: A Case Study in Hearing Loss

It seems unlikely that people living in one of the quietest places on earth would suffer from hearing loss. But deafness is just what neurophysiologist Allen Counter discovered among the Inuit (formerly called Eskimos) living in the northern Greenland village of Moriussaq. Counter found that males in this community begin losing their hearing at about the age of 10. Their hearing diminishes steadily throughout their lives until, by the age of 60, most Inuit men have lost most or all of their hearing. Girls and women, by contrast, experience little or no hearing loss for the duration of their lives.

To find the explanation for hearing loss among Inuit men, Counter went out onto the ice. Following the men on their seal hunts, he observed the likely cause of their problem. While traditionally, hunters used harpoons to spear seals, modern Inuit hunters use rifles. They wait at the seals' breathing holes and, when the animals come to the surface for a breath, they shoot. Exposure to these sudden and extremely loud explosions of gunfire, again and again over many years, Counter hypothesized, must be the cause of the progressive hearing loss he observed in the men. Lab tests confirmed his hypothesis and also provided a physiological explanation for how it happens.

At the end of the canal leading into the ear there is a tough membrane known as the tympanic membrane, or eardrum. When sound waves reach the eardrum, they cause it to vibrate. These vibrations, in turn, are transferred along three small, interconnected bones into a snail-shaped, fluid-filled tube called the cochlea. The cochlea is lined with receptor cells that have microscopic hairlike structures called stereocilia emanating from them. Receptor cells transform the vibrations that stimulate the stereocilia into electric signals that are picked up by nerve calls and are perceived by the brain as sound.

Sudden loud noises like gunshots, however, flatten the stereocilia, just as a strong gust of wind can knock down trees. And while some receptor cells survive and recover from being battered by loud sounds, others are damaged beyond repair. Indeed, field tests of the Inuit showed that after each gunshot, the hunters experienced a temporary loss of hearing, followed by recovery. The recovery was seldom complete, however. Each time, the hunters' hearing returned, but not to the same level as before. They lost receptor cells, and hearing, one gunshot at a time.

While researchers like Allen Counter are working to develop artificial cochleas, they have had very little success thus far. According to doctors, the best cure for hearing loss, now and probably for a very long time, is no cure at all: It is prevention. Doctors recommend that people working in loud environments, using loud machinery, and certainly firing guns, use adequate ear protection.

Would you expect people who live in the Arctic to have a more-acute or less-acute sense of hearing? Explain your reasons.

How has the changing way of life for the inhabitants of the Arctic resulted in widespread early hearing loss?

Are people in your community exposed to loud noises that might cause hearing loss? Do you think people are aware of the effects of noise and how hearing loss can be prevented?