A rather small study has suggested that the difficulty processing speech that older adults face is due to more than age-related hearing loss. The findings imply that part of the equation rests in how the aging brain struggles to interpret competing sound signals.
The study looked at 32 native English-speakers with clinically normal hearing. The participants were divided into a younger adult (average age 22) and older adult (average age 65) group. They were then measured in what is known as the Quick Speech-in-Noise (QuickSIN) test, which measures speech comprehension in quiet environments, as well as in environments with four distinct levels of background noise, and where more than one person is talking. Additionally, participants were given scans that measured midbrain and cortex activity.
The researchers found that the older group had trouble tracking speech across all of the QuickSIN components. The older adults took more time to process the acoustic cues and scored lower on speech comprehension in noise. Neurologically, the midbrain and cortical responses in the brain were also more degraded. This, to the researchers, suggests that the reason older adults have trouble with speech comprehension is not just that they do not hear as well, but that the information is not processed the same way.
What This Means
Aside from adding a bit of extra context to how older people might struggle to understand speech, the researchers also produced an accompanying article that adds some extra clarification to the findings. They noted that older adults in part compensate for age-related hearing and comprehension difficulties by relying more on contextual clues. For instance, older adults are much better at following a conversation if the target’s speech has a lot of contextual content, or a background distraction is not meaningful or intelligible (such as being in a foreign language). The brain scans supported this idea by showing that the cortical responses were less deteriorated when the older listener was faced with incomprehensible background noise.
This suggests that an older person could improve their comprehension by minimizing background noise that could be confused with the targeted speech.
Presacco, A., et. al., “Effect of informational content of noise on speech representation in the aging midbrain and cortex,” Journal of Neurophysiology, 2016; 10.1152/jn.00373.2016.
Presacco, A., et. al., “Evidence of degraded representation of speech in noise, in the aging midbrain and cortex,” Journal of Neurophysiology, 2016; 10.1152/jn.00372.2016.
“Ability to process speech declines with age,” Science Daily web site, October 4, 2016; https://www.sciencedaily.com/releases/2016/10/161004130347.htm, last accessed October 5, 2016.