Growing older can take a toll on your hearing, but even more than your age, a new study has revealed another biological factor that may influence how your ears respond to sound: your sex.
According to an international study, “women consistently exhibit higher sensitivity” to loud clicking noises at low, mid, and high frequencies.
When the ear is stimulated in this way, researchers found the hairs inside the cochlea of women were two decibels more sensitive, on average, than the cochlear hairs of men. While this may not be noticeable to an individual, it is measurable in a cochlear test.
The findings provide “compelling evidence” that the inner ears of women are more sensitive to sounds than the inner ears of men.
“Age is a well-established factor in the decline of cochlear sensitivity,” write the authors, led by evolutionary biologist Patricia Balaresque from Paul Sabatier University in France. “However, in our study, the effect of age is overshadowed by sex and environmental factors.”
Using a click test called Transient-Evoked Otoacoustic Emissions (TEOAE), researchers analyzed the cochlear sensitivity of 448 healthy participants from five different countries: Ecuador, England, Gabon, South Africa, and Uzbekistan.
In all the analytical models the team ran, sex was the main biological factor explaining inter-individual differences in TEOAE results. Age came second.
When the authors turned to non-biological factors, they found where a person lived had a greater impact on their cochlear sensitivity than their age. Those who live in forest environments, for instance, tend to outperform those in high-altitude or urban environments.
“Our findings challenge existing assumptions and highlight the need to consider both biological and environmental factors when studying hearing,” says Balaresque.
“Identifying drivers behind natural hearing variation will improve our understanding of hearing loss and individual differences in noise tolerance.”
Initial research indicates that as males age, they lose their hearing twice as fast as their female counterparts, and that is especially true for higher frequency sounds.
Scientists still don’t understand why that is. Some have proposed that men are exposed to more damaging noises in their lives, which could exacerbate age-related hearing loss, but these new results suggest sex differences in cochlear sensitivity cannot simply be explained by age or by environmental exposure.
Some previous studies have found that women exhibit subtle yet higher sensitivity on TEOAE tests when the click is at least above 2,000 hertz (Hz), while other studies have found no differences between the sexes.
This field of research remains relatively unexplored, but Balaresque and her colleagues have now put forward a few hypotheses.
Sex differences in cochlear sensitivity, they explain, could be due to hormone exposure during early-life development, possibly influencing how tiny hairs in the cochlea form, gather, and respond to sound.
Women also tend to perform better in other tests of hearing, which suggests they may have “superior” inner and outer ear function compared to men. Whether that is due to cultural or biological factors needs more research.
“We don’t really know why this might be, but given the detrimental effect of noise on overall health such as sleep quality and increased cardiovascular disease, having more sensitive hearing in noisy environments may not always be a good thing,” explains evolutionary biologist Turi King from the University of Bath in the UK.
The study is one of the first detailed investigations of what influences the sensitivity of the human inner ear using a diverse cohort with a variety of ethnicities and languages considered.
The robust sex-based differences the authors identified now need to be studied further. Identifying what drives hearing loss and noise tolerance will be essential when it comes to tailoring hearing aids to diverse populations, the team concludes.
The study was published in Scientific Reports.
