There is increasing evidence linking the onset of dementia to poor sleep quality and depression. Both have been identified as key risk factors, along with traumatic injury to the brain, said Professor Kristine Yaffe, a visiting expert on dementia from the University of California in San Francisco.

Prof Yaffe, this year’s Oon Chiew Seng Speaker, was here in March to speak about research in this field. She said that that these findings add to what scientists already know about diabetes and obesity and the risk they pose to adults and middle-aged people. Dementia, the debilitating and life-sapping illness that robs sufferers of their memory, identity and dignity, affects more than 46.8 million people worldwide. In Singapore, dementia affects 40,000 people today; the number of people diagnosed with the illness is expected to double to 80,000 by 2030.

In two lectures delivered at NUS Medicine, Prof Yaffe dwelt on ways to prevent dementia through changing lifestyle factors and the link between sleep and the risk of dementia. The lectures are part of the Oon Chiew Seng Distinguished Visitor Programme, established in 2011 through a donation by NUS Medicine alumna Dr Oon Chiew Seng to bring in world-renowned experts to share their knowledge.

“Many, many things change with ageing in terms of sleep, and it is becoming very clear that this is something we have not paid enough attention to, and that there are huge connections with metabolic disease, cardiovascular disease, and dementia,” said Prof Yaffe.

Sleep disturbance is common in older adults and affects up to 50% of older people, said Prof Yaffe. These older adults suffer from decreased sleep quality, overall less restorative sleep, shifted circadian rhythms and sleep apnea.

Studies have shown that poor sleep quality may be a risk factor for cognitive impairment and dementia, but these epidemiological investigations have been limited by cross-sectional design and subjective measures of sleep quality.

Professor Yaffe’s recent studies on older adults have linked objectively measured sleep variables, including sleep efficiency, changes in sleep architecture, and periodic limb movements, to cognitive impairment. These findings also suggest that these associations may be bidirectional. Abnormal circadian rhythms and sleep disordered breathing may also increase the risk of dementia, according to Professor Yaffe’s research.

While further exploration of the mechanism of these associations is needed, modification of sleep quality could be a promising target for dementia prevention, as sleep disorders and disturbances are often treatable, she said.


Another likely culprit responsible for the onset of dementia is depression, according to research. The earlier depression or its symptoms are treated, the lower the likelihood that it will lead to dementia, said Prof Yaffe, whose research proved that the burden of depressive symptoms over time increases the risk of dementia. She suggested that older adults should be monitored more aggressively for the onset of new depressive symptoms.

“Public health strategies at the societal level can impact dementia trends, in addition to improved education and economic well-being,” she added.

Traumatic brain injury too increases the risk of dementia, though more research on treatment and rehabilitation needs to be done to potentially reduce dementia risk in future, added Prof Yaffe.

The two things Professor Yaffe believe Singaporeans can do to prevent dementia are engaging in physical activity and keeping cardiovascular disease at bay.

“My understanding is that people now are less active than they used to be, and there are a lot of heart disease risk factors such as diabetes, hypertension and stroke. These two areas are important for dementia, and they seem to have a 

Professor Kristine Yaffe giving a public lecture on lifestyle factors that could prevent dementia, at the NUHS Tower Block Auditorium on February 27, 2017.

lot of connections for Singapore. The world should expect more research studies on dementia in time to come. But for now, everyone should take responsibility in delaying dementia.”

Referring to a 2001 study of 5,925 elderly women in their seventies and eighties, Prof Yaffe said she found that the more blocks they walked in their neighbourhoods over six to eight years, the less they suffered from the risk of cognitive decline. It also showed that exercising improves cognitive function in older adults with memory complaints.

Observational studies have also shown that dementia is lower in people with more education, higher intelligence quotient (IQ), and greater occupational achievement, as well as in those who engage in mentally stimulating leisure activities. This was supported by another piece of research, in 2011. It showed that, in older adults without dementia, lower amyloid beta (β-amyloid) 42/40 levels – amino acids in human brains known to cause Alzheimer’s disease were not as closely associated with cognitive decline over nine years in more highly educated people than in those with a lower-than-high-school education. These results are important as biomarkers such as plasma β-amyloid are relatively easy to obtain and minimally invasive, and can contribute to better dementia treatment.

While a cure for dementia may not be on the horizon, Professor Yaffe believes that more research on dementia and its risk factors will allow for better treatment in future.

“I’m not sure I see a cure, but I think we will have much better medications, and my prediction is that dementia will be like heart disease, where you give (the patient) a couple of different medications combined with lifestyle (changes). We need not ever be able to cure or have the disease go away completely, but we will be able to manage it better so the symptoms are less and do not progress as quickly,” she said.

For those afflicted with dementia, a change of perspective and preventing a worsening of the symptoms may be all they need.

“Once somebody has dementia, you cannot expect to go back to when you were 30, but you can have other ways of having meaning and quality of life and productivity. You have to change your perspective. You want to be active, so doing things, stimulating your brain, moving your body, connecting with people are all very important. The other one is preventing cardiovascular disease risk, and taking what is good for the heart, that is good for the brain.”