This discovery opens up a new method to treat patients with hearing loss.
So what is a Circadian rhythm? According to the National Institute of General Medical Sciences, Circadian rhythms are physical, mental and behavioural changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism’s environment. They are found in most living things, including animals, plants and many tiny microbes. The study of Circadian rhythms is called chronobiology.
The Science Daily article says that important body functions, such as sleep, the immune system, and hormone levels are controlled by this inner clock. A team of researchers at Karolinska Institutet have discovered that there is also a biological clock in the ear, controlled by genes known to regulate Circadian rhythms. The article explained:
- By measuring the activity of the auditory nerve, researchers found that mice exposed to moderate noise levels during the night suffered from permanent hearing damages while mice exposed to similar noise levels during the day did not.
- The ability to heal after hearing damage was therefore linked to the time of day during which the noise damage occurred, and here the ear's Circadian clock played an important role.
- The growth hormone, BDNF (brain-derived neurotrophic factor), known to protect auditory nerve cells, fluctuates throughout the day. When mice were exposed to noise during daytime, their concentration of BDNF in the ear increased, which protected them from permanent hearing damage. This protective response was absent at night.
- Researchers succeeded in tricking the mice's ear clocks in an experiment where they exposed mice to noise at night while stimulating BDNF at the same time. Mice were then protected from permanent hearing loss as their auditory nerve cells successfully recovered from noise injury.
What does this mean to you? These findings, published in the journal Current Biology, may explain why we have different levels of noise sensitivity during different times of the day. The discovery may pave the way for new treatment methods for hearing damage, which affects between 10 and 15 per cent of the population.
According to the Hearing Foundation of Canada, the cost of hearing loss to the Canadian economy could be in the tens of billions of dollars. A 2006 Australian study estimated that costs to that nation’s economy from hearing loss amounted to $10.6 billion per year. On a per capita basis, this could mean a Canadian equivalent of almost $18 billion per year.
Connect Hearing Audiologist & Director of Professional Practice MJ Desousa says people should be excited about the benefits this study will have in the fight against hearing loss.
“At Connect Hearing, we see the numbers and we realize the impact hearing loss is having on Canadian society and the world, so I am always encouraged when I see breakthroughs in research. What we have here is really good news,” said Desousa. “This study opens up a whole new way of thinking in the way researchers can approach the fight against hearing loss. Researchers are doing their part in this fight, but we also want the public to do theirs. And they can pitch in by being more mindful about their hearing health and the hearing health of their loved ones.”