Researchers find amplitude more influenced by sex than age

Scientists have found that sex is the leading factor explaining differences in hearing sensitivity, with women having significantly more sensitive hearing than men.

Hearing problems are on the rise worldwide, and while hearing sensitivity is well known to decrease with age, little research has been done on the other biological and environmental factors that influence them, such as sex, ear side, language, ethnicity, and local environment.

The team, led by Dr. Patricia Balaresque from the Center for Biodiversity and Environmental Research (CRBE) in Toulouse (France) and including Professor Turi King from the University of Bath (UK), conducted hearing tests for 450 individuals across 13 global populations—Equador, England, Gabon, South Africa, and Uzbekistan.

These populations were selected to capture a wide range of ecological and cultural contexts, including underrepresented rural and non-European groups.

They investigated the sensitivity of the cochlea in the ear, looking at how it transmitted brain signals in response to different amplitudes and frequencies of sound by measuring so-called Transient-Evoked Otoacoustic Emissions (TEOAE).

It’s already well known that people generally have better hearing in their right ear, compared with their left, and that hearing usually declines with age. However, the researchers were surprised by their results on the effects of sex and the environment.

Their findings, published in the journal Scientific Reports, show that hearing amplitude is more influenced by sex than age, with women showing an average of two decibels more sensitive hearing than men across all the populations studied.

The second most significant influence was the environment, which not only affected the response to volume but also the range of frequencies of sound perceived.

People living in forest areas had the highest hearing sensitivity and those living at high altitudes had the lowest.

They found that population, environment, and language all significantly contribute to the variation in hearing across human groups, but it wasn’t clear whether this was due to the whole body being affected by the environment or due to long-term adaptations to varying soundscapes, noise levels, or exposure to pollution.

The researchers suggest that people living in forests could have higher sensitivity because they’ve adapted to soundscapes with lots of non-human sounds, where vigilance is essential for survival. Or it could be due to being exposed to lower levels of pollution.

People living at higher altitudes may have reduced sensitivity due to a number of reasons, including the impact of lower atmospheric pressure on measurements, potential sound reduction in high altitude environments, or physiological adaptations to lower oxygen levels.

The team also found a difference between urban and rural populations, with those living in cities having a shift towards higher frequencies, possibly due to filtering out low-frequency traffic noise.

Professor Turi King, director of the Milner Center for Evolution at the University of Bath, collected samples from the UK participants while in her previous role at the University of Leicester, and is a co-author on the study. She said, “We know that hearing generally declines with age and that exposure to loud noise and chemicals such as tobacco smoke can damage hearing.

“We wanted to investigate in more detail what factors shape our hearing and the diversity of hearing sensitivities and see how our hearing has adapted to our local environment.

“We were surprised to find that women had two decibels more sensitive hearing across all the populations we measured, and this accounted for most of the variations between individuals. This could be due to different exposure to hormones during development in the womb, due to men and women having slight structural differences in cochlear anatomy.

“As well as having higher hearing sensitivity, women also perform better in other hearing tests and speech perception, indicating that their brains are also better at processing the information. 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.”

Dr. Patricia Balaresque, who led the study at CRBE, said, “Our findings challenge existing assumptions and highlight the need to consider both biological and environmental factors when studying hearing. Identifying drivers behind natural hearing variation will improve our understanding of hearing loss and individual differences in noise tolerance.”

Professor King said, “We know that humans are continuing to evolve, so the next question is whether our hearing is able to change in response to different environments generally or whether there are genetic adaptations involved.”

Scientists have found that sex is the leading factor explaining differences in hearing sensitivity, with women having significantly more sensitive hearing than men.

Hearing problems are on the rise worldwide, and while hearing sensitivity is well known to decrease with age, little research has been done on the other biological and environmental factors that influence them, such as sex, ear side, language, ethnicity, and local environment.

The team, led by Dr. Patricia Balaresque from the Center for Biodiversity and Environmental Research (CRBE) in Toulouse (France) and including Professor Turi King from the University of Bath (UK), conducted hearing tests for 450 individuals across 13 global populations—Equador, England, Gabon, South Africa, and Uzbekistan.

These populations were selected to capture a wide range of ecological and cultural contexts, including underrepresented rural and non-European groups.

They investigated the sensitivity of the cochlea in the ear, looking at how it transmitted brain signals in response to different amplitudes and frequencies of sound by measuring so-called Transient-Evoked Otoacoustic Emissions (TEOAE).

It’s already well known that people generally have better hearing in their right ear, compared with their left, and that hearing usually declines with age. However, the researchers were surprised by their results on the effects of sex and the environment.

Their findings, published in the journal Scientific Reports, show that hearing amplitude is more influenced by sex than age, with women showing an average of two decibels more sensitive hearing than men across all the populations studied.

The second most significant influence was the environment, which not only affected the response to volume but also the range of frequencies of sound perceived.

People living in forest areas had the highest hearing sensitivity and those living at high altitudes had the lowest.

They found that population, environment, and language all significantly contribute to the variation in hearing across human groups, but it wasn’t clear whether this was due to the whole body being affected by the environment or due to long-term adaptations to varying soundscapes, noise levels, or exposure to pollution.

The researchers suggest that people living in forests could have higher sensitivity because they’ve adapted to soundscapes with lots of non-human sounds, where vigilance is essential for survival. Or it could be due to being exposed to lower levels of pollution.

People living at higher altitudes may have reduced sensitivity due to a number of reasons, including the impact of lower atmospheric pressure on measurements, potential sound reduction in high altitude environments, or physiological adaptations to lower oxygen levels.

The team also found a difference between urban and rural populations, with those living in cities having a shift towards higher frequencies, possibly due to filtering out low-frequency traffic noise.

Professor Turi King, director of the Milner Center for Evolution at the University of Bath, collected samples from the UK participants while in her previous role at the University of Leicester, and is a co-author on the study. She said, “We know that hearing generally declines with age and that exposure to loud noise and chemicals such as tobacco smoke can damage hearing.

“We wanted to investigate in more detail what factors shape our hearing and the diversity of hearing sensitivities and see how our hearing has adapted to our local environment.

“We were surprised to find that women had two decibels more sensitive hearing across all the populations we measured, and this accounted for most of the variations between individuals. This could be due to different exposure to hormones during development in the womb, due to men and women having slight structural differences in cochlear anatomy.

“As well as having higher hearing sensitivity, women also perform better in other hearing tests and speech perception, indicating that their brains are also better at processing the information. 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.”

Dr. Patricia Balaresque, who led the study at CRBE, said, “Our findings challenge existing assumptions and highlight the need to consider both biological and environmental factors when studying hearing. Identifying drivers behind natural hearing variation will improve our understanding of hearing loss and individual differences in noise tolerance.”

Professor King said, “We know that humans are continuing to evolve, so the next question is whether our hearing is able to change in response to different environments generally or whether there are genetic adaptations involved.”