SINGAPORE - One in 10 people aged 60 and above in Singapore has dementia, according to a new nationwide study.

Findings on how common the illness is and its impact on caregivers emerged on Wednesday from the $4.4 million Well-being of the Singapore Elderly (WiSE) study, which interviewed almost 5,000 seniors and their family members.

Its growing prevalence is a concern, according to Institute of Mental Health experts who collaborated with other international investigators for the three-year research.

Most countries have a prevalence rate of 5 to 7 per cent, though researchers from IMH said countries that used the same diagnostic tool as the one in the WiSE study, such as urban China and India, registered an 8 per cent prevalence.

A World Health Organisation survey on ageing carried out here 20 years ago found that only 3 per cent were diagnosed with dementia.

Professor Chong Siow Ann, vice-chairman of the IMH's medical board (research), who led the WiSE study, said: "The concern is how we can use the study to assess if we have adequate resources to meet the challenges we have right now and those that are going to be emerging."

IMH experts attribute the rise in prevalence rate to a rapidly ageing population and increasing prevalence of stroke, obesity, diabetes and hypertension that are risk factors for dementia.

Patients with dementia, a progressive brain disorder, may suffer from memory loss and have difficulty expressing themselves.

In 2012, about 28,000 people in Singapore aged 60 and older had dementia. The number is expected to soar to 80,000 by 2030.

The study also found that age, stroke as well as education and employment were associated factors.

Caregivers of those with dementia also report significantly higher levels of distress and psychological problems compared to other caregivers.