SINGAPORE - Older Singaporeans who lose their hearing are 2.3 times more likely to develop mild cognitive impairment or dementia, a local study has found.

Early diagnosis and intervention for hearing loss could therefore potentially delay dementia and cognitive decline, experts say.

This is significant, given that more than 60 per cent of Singaporeans aged over 60 experience some form of hearing loss, according to the National University of Singapore and Ng Teng Fong General Hospital, which were behind the study.

The study involved 1,515 Singaporeans, aged 55 and above, who went through two rounds of cognitive and clinical assessments at regular intervals of approximately three years. They had normal memory and thinking skills at the start.

It is part of the larger, long-term Singapore Longitudinal Ageing Study, which is led by Associate Professor Ng Tze Pin from the department of psychological medicine at the National University of Singapore's (NUS) Yong Loo Lin School of Medicine.

"This is the first longitudinal ageing study in Singapore and Asia that supports emerging evidence around the world that hearing loss is a risk factor for dementia," said Dr Rebecca Heywood a consultant at the ear, nose & throat, head & neck surgery department at Ng Teng Fong General Hospital who was the study's principal otolaryngology researcher.

In Singapore, almost a quarter of the population will be over 65 by 2030 and the prevalence of dementia in adults over 60 is currently about 10 per cent.

Dementia, which takes many years to develop, occurs as a result of several factors. Most of these, including hearing loss, can be modified with suitable lifestyle changes, said Prof Ng.

While hearing loss does not cause mental decline or dementia by itself, the results show a link between untreated hearing loss and more rapid cognitive decline.

Dr Heywood said there are a few theories on how hearing loss and dementia are connected.

"For example, those with hearing loss need more effort to hear a degraded sound, so less brain resources are available for thinking and memory," she said.

"Hearing loss results in less auditory stimulation and as a result, the hearing areas in the brain which are also involved in memory, become underused and decline in function."

It is also possible that hearing loss may give rise to social isolation, which is itself a risk factor for cognitive decline, she added.

However it can be treated using technologies such as hearing aids and cochlear implants.