Experts: Control hypertension to cut risk of dementia

It is top factor for silent strokes, which cause significant number of vascular dementia cases
By Salma Khalik, Senior Health Correspondent, The Straits Times, 1 Feb 2017

The number of people getting dementia in Singapore could be cut by more than a third, if only those with hypertension were able to keep their blood pressure under control.

This is because more Asians than Caucasians suffer from a type of dementia that is caused by "silent" strokes.

Amid the rising incidence of dementia, there should be more education on the dangers of high blood pressure and how to manage the condition, experts urged.

"Partnership with primary care services will be crucial," said Associate Professor Nagaendran Kandiah, a senior neurologist at the National Neuroscience Institute (NNI), noting that most patients with high blood pressure are being treated by general practitioners and polyclinic doctors.

Dementia, or the severe decline of mental ability, including memory and judgment, affects about 40,000 people in Singapore today. It is expected to double to 80,000 by 2030 as the population ages.

The NNI has been seeing more dementia patients, said Prof Kandiah, with numbers rising from 1,324 in 2014 to 2,246 last year.

Of them, two in five suffer from vascular dementia. And this is where the link to hypertension comes in.

A "significant" number of vascular dementia cases here are caused by silent or micro strokes, for which high blood pressure is the biggest factor, said Professor K. Ranga Rama Krishnan, a dementia expert. High blood pressure leads to the narrowing of blood vessels, including those in the brain, so they become blocked more easily, raising a person's risk of getting a stroke by up to six times.

Prof Krishnan, who is the dean of Rush Medical College in the United States and chairman of Singapore's National Medical Research Council, said 15 per cent of people in general would have had one or more silent strokes by the age of 65.

A silent stroke occurs deep in the brain when a blood vessel is clogged, cutting off the blood supply to the brain cells there.

The cumulative effect of many such silent strokes can lead to dementia, he said.

Good control of blood pressure reduces one's risk of getting silent strokes and hence dementia, added Prof Krishnan.

NNI's Prof Kandiah said that the incidence of vascular dementia here is more than double that of Western countries.

Some strokes cause symptoms such as slurred speech or paralysis, but there are also silent strokes which show no outward affect.

"We are seeing a lot of silent strokes in Asians, more than in Caucasians. The type of blood vessels affected are different, smaller," he said, adding that no one knows why.

"A simple thing like hypertension, if it is well treated, would make a significant difference in terms of dementia numbers."

Other risk factors for strokes, both silent and overt, are diabetes, smoking, high cholesterol levels and a sedentary lifestyle.

Control of these risk factors has to start when one is about 30, he said, as the effect is cumulative.

However, it is still not too late to take action at the point of mild cognitive impairment (MCI), a condition that precedes dementia.

People with MCI may feel they are performing below their usual level in their mental abilities, such as thinking, memory, language skills and judgment.

Prof Kandiah said a study in Canada found that one in five people aged 50 to 60 and one in three over the age of 65 have MCI. Annually, 17 per cent of those with MCI would progress to dementia.

Generally, it takes three to four years to go from MCI to mild dementia, and another similar duration of time for it to progress to severe dementia, where a person is no longer able to function without aid.

However, MCI gives the "best window of opportunity" for intervention, Prof Kandiah said.

If a person controls his chronic ailments, stops smoking and starts doing physical and mental exercises, the onset of dementia could be delayed.

Prof Krishnan said doing that slows down the worsening by 10 per cent to 15 per cent, and new studies show that exercise causes the brain to grow new brain cells. But experts are still unsure of how useful those new brain cells are.