Hearing impairment is associated with accelerated cognitive decline with age, though the impact of mild hearing loss may be lessened by higher education, researchers say.

The findings suggest that those with more serious hearing impairment had worse performance at the initial visit on a pair of commonly used cognitive assessment tests. However, the association of mild hearing impairment with rate of cognitive decline was modified by education, said the researchers at University of California, San Diego.

"We surmise that higher education may provide sufficient cognitive reserve to counter the effects of mild hearing loss, but not enough to overcome effects of more severe hearing impairment," said senior author Linda K. McEvoy, Professor at the varsity.

For the study, published in the Journal of Gerontology: Series A Medical Sciences, the research team tracked 1,164 participants with a mean age 73.5 years of whom 64 per cent were women. All had undergone assessments for hearing accuracy and cognitive function between 1992 and 1996 and had up to five subsequent cognitive assessments at approximately four-year intervals. None used a hearing aid.

They found that almost half of the participants had mild hearing impairment, with 16.8 per cent suffering moderate-to-severe hearing loss. The team said that mild hearing impairment was associated with steeper decline among study participants without a college education, but not among those with higher education.

Mild hearing impairment was associated with steeper decline among study participants without a college education, but not among those with higher education. Moderate-to-severe hearing impairment was associated with steeper cognitive decline regardless of education level, the researchers said.