Researchers have found a close relationship between losing your hearing and losing your memory and believe the former could be used as an early warning or the latter.

They say that interventions that could delay the onset of dementia by even one year could lead to a more than 10pc decrease in the prevalence of dementia by 2050.

Dr Frank Lin, of Johns Hopkins Medical Institutions in Baltimore, and colleagues studied 639 individuals age 36 to 90 without dementia.

Participants initially underwent cognitive and hearing testing between 1990 and 1994 and were followed for the development of dementia and Alzheimer's disease through to May 31st, 2008.

Of the participants, 125 had mild hearing loss (25 to 40 decibels), 53 had moderate hearing loss (41 to 70 decibels) and six had severe hearing loss (more than 70 decibels).

During a midpoint follow-up of 11.9 years, 58 individuals were diagnosed with dementia, including 37 who had Alzheimer's disease.

The risk of dementia was increased among those with hearing loss of greater than 25 decibels, with further increases in risk observed among those with moderate or severe hearing loss as compared with mild hearing loss.

For participants age 60 and older, more than a third (36.4pc) of the risk of dementia was associated with hearing loss.

The risk of developing Alzheimer's disease specifically also increased with hearing loss, such that for every 10 decibels of hearing loss, the extra risk increased by 20pc.

Dr Lin said that the two conditions may share the same cause.

"Hearing loss may be causally related to dementia, possibly through exhaustion of cognitive reserve, social isolation, environmental deafferentation [elimination of sensory nerve fibres] or a combination of these pathways," he said.

"If confirmed in other independent cohorts, the findings of our study could have substantial implications for individuals and public health.

By the year 2050, an estimated 100 million people or nearly one in 85 individuals worldwide will be affected by dementia.

The research was published in the Archives of Neurology.