Now hear this

Joe’s Wife:  Jerry just called from Brown’s Boat Basin. 

Old Joe:  Who fell down?  Did you say Larry or Mary? And what’s that about a brown raisin in your throat?

Joe’s Wife:  “YOUR SON JERRY PHONED.  Said he wants to talk with you about coming over for dinner.

Old Joe:  “Oh.  OK.  I would love to go for a walk with him.  And Rover can come too.  He is really a winner.”

Joe’s Wife:  “You mostly don’t get it.  YOU NEED TO GET YOUR HEARING CHECKED.”

Old Joe:  “My hearing is fine.  You need to speak up more clearly.  Now, what were you trying to say?

Joe’s Wife:  Never mind.  Forget it.   I am going shopping.

Social isolation is only one likely consequence of hearing loss(ref) for an older person. “More than 28 million people in the United States have a significant loss of hearing. Almost half of these individuals are under the age of 65, and 54% of the population over 65 years of age have hearing loss. Hearing loss is the third most prevalent chronic health condition in the older population, following arthritis and high blood pressure. The impact of hearing loss can be far reaching and involve many different aspects of one’s life. Hearing impaired individuals may have difficulty localizing sounds, understanding speech in noisy environments, and contributing to conversations. This can lead to social isolation, confusion, frustration, tension, stress and depression. There is mounting evidence that untreated hearing loss has enormous impact on the overall health of individuals(ref). “ 

I set out to research age-related hearing loss and what if anything can be done about it.  This is what I came up with including some relatively good news.

The classical explanation is that hearing loss is something that often comes with the territory of growing older.  It is called Presbycusis and if you have it there is probably nothing that can be done about it except to get a hearing aid or a cochlear implant if you want to go that far.  Hearing loss is mostly at higher frequencies resulting in fricatives and sibilants often being misrecognized and involves multiple changes in hair cells, nerve fibers and molecular markers(ref).  A simplified view is “Tiny hairs inside your ear help you hear. They pick up sound waves and change them into the nerve signals that the brain interprets as sound. Hearing loss occurs when the tiny hairs inside the ear are damaged or die. The hair cells do not regrow, so most hearing loss is permanent(ref).”  Also, hearing loss can be accelerated by repeated exposure to loud noises such as in a rock concert, cigarette smoking and some drugs and diseases. “About half of all people over age 75 have some amount of age-related hearing loss(ref).”  If an older person experiences hearing loss the first step is to confirm that the problem is not just accumulated ear wax, then to get tested by an audiologist to confirm the loss, and then most-often to get fitted with a hearing aid. 

Starting in the 1990s, a large number of studies have established that antioxidants can partially or even in large measure reduce the loss of hearing induced by loud noise, disease or other events traumatic to hearing in a variety of animal models(ref).  “The hearing loss from exposure to noise and ototoxic drugs share a number of audiological and pathological similarities. Recent research has shown that reactive oxygen species (ROS) may be a common factor in both noise- and drug-induced hearing loss. This review describes three experiments that point to ROS as a causative factor in both noise- and drug-induced hearing loss and antioxidants as a protective agent(ref).”  “The pathways of necrotic and apoptotic cell death are also reviewed. Interventions are discussed that target the prevention of noise-induced hair cell death: the use of antioxidants to scavenge and eliminate the damaging ROS, pharmacological interventions to limit the damage resulting from ROS, and new techniques aimed at interrupting the apoptotic biochemical cascade that results in the death of irreplaceable hair cells(ref).”  “– animals treated with MLT (melatonon) experienced an improvement in their hearing functionality. This effect, which is probably linked to MLT’s ability to reduce c-fos and TNF-alpha gene expression thereby preventing outer hair cell (OHC) loss, was even more pronounced in week 3(ref).”  “In this study, experiments provide compelling evidence that long-term treatment with compounds that block or scavenge reactive oxygen metabolites attenuate age-related hearing loss and reduce the impact of associated deleterious changes at the molecular level(ref).”  

·        The view of age-related hearing loss started to shift then too, to where it was seen to a large extent to be the result of accumulated oxidative damage.  This view brings hearing loss into very familiar territory, as being associated with the Oxidative Damage theory of aging.  It also strongly suggests that taking antioxidants might be very useful for staving off age-related hearing loss.  See the supplement firewall for the oxidative damage theory of aging.  Substances in the combined anti-agingfirewall experimentally demonstrated to reduce noise-trauma hearing loss include Vitamins A, C, E,  magnesium, resveratrol, acety l-carnitine, melatonin, folic acid, and R-alpha lipoic acid.  

·         As a variation on this oxidative damage theory of hearing loss, some researchers started to suspect mitochondrial damage as being a serious culprit(ref), bringing us to another island of familiar territory, the Mitochondrial Damage theory of aging.  Again, substances in the firewall for the mitochondrial damage theory of aging appear to be effective against hearing loss. “Acetyl-l-carnitine and alpha-lipoic acid reduce age-associated deterioration in auditory sensitivity and improve cochlear function. This effect appears to be related to the mitochondrial metabolite ability to protect and repair age-induced cochlear mtDNA damage, thereby upregulating mitochondrial function and improving energy-producing capabilities(ref).” 

·        Starting in the 2000s, yet-another view of age-related hearing loss has been emerging, seeing presbycusis as a result of decline in the rate of differentiation of hair follicle stem cells in the cochlear canal.  All along it has been known that hearing is the result of movement by sounds of delicate hairs in the cochlea and that presbycusis is directly associated with decline in the numbers of such hairs and corresponding hair cells.  More and more of the hair cells die out with age and are not replaced and hearing goes downhill.  And cochlear hair cells do not live in isolation; their wellbeing is correlated with the wellbeing of associated nerve cells like spiral ganglion neurons.  “- – neurotransmitter release from the hair cells drives membrane electrical activity in spiral ganglion neurons which also supports their survival(ref).  “The recent discovery of stem cells in the adult inner ear that are capable of differentiating into hair cells, as well as the finding that embryonic stem cells can be converted into hair cells, raise hope for the future development of stem-cell-based treatment regimens(ref).  This new stem-cell view of hearing loss leads to yet-another island of familiar territory – the Decline in Adult Stem Cell Differentiation theory of aging.   

·        Various means(ref) are being considered to remedy this situation in old folks, one being to make new cochlear hair follicle cells out of induced pluripotent stem cells and re-introduce them into the cochlea(ref).  This might be a good idea for the longer run but in the shorter run a simpler approach may be use of telomerase activation to increase the rate of differentiation of the existing hair follicle stem cells.  We know that telomerase can increase the rate of differentiation of hair stem cells via a process independent of telomere extension(See the shaggy mouse story). 

And I know from personal experience (N=1) that since starting telomerase activation many months back I am slowly getting more and more grey hairs on my previously-bald scalp.  Now, am I also getting more hairs in my cochlea?  Possibly; it is hard to count them.  Is my hearing improving?  Not insofar as I can tell.  My hearing right now is definitely not as good as it was back 5 years ago when I was only 74 but my immediate problem could simply be ear wax.   I will be cleaning my outer ear and watching carefully (actually listening carefully) to see what direction my hearing is going in.