Warnings of dementia epidemic could be overblown, admit scientists

Predictions that Britain and other Western nations will experience a dementia epidemic as the population grows older may have been overblown, scientists have said.

A review of five previous studies in the UK, Sweden, the Netherlands and Spain has found signs that the number of people with Alzheimer’s and other forms of dementia is “stabilising”.

The researchers who carried out the work said that previous predictions of the dementia epidemic were based on research carried out 20 years ago, which may now be out of date given recent changes in health and lifestyle that can protect people against the condition.

The study found that the number of people with dementia in 2010 was about 670,000, which is about the same as it was in 1990, despite the population getting older and so being at greater risk of the disease.

“For the UK our estimate is that the number of people with dementia now is about the same as it was 20 years ago, based on the same diagnostic criteria, despite sustained population ageing,” said Carol Brayne, professor of public health medicine at Cambridge University, who led the study.

However, other scientists warned that the population of Britain will continue to age over the coming decades and the fastest-growing age group will be people over 85, who stand a 40 per cent chance of suffering from dementia – leading to an almost inevitable growth in the degenerative brain disease.

Nevertheless, the study found that a healthy lifestyle, improvements in living conditions and better education about how to lead an active life in older age are all contributing to a fall in the risk of developing dementia.

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These changes are at odds with previous research that led to dire predictions about an impending dementia epidemic, the researchers said.

“These old studies support the idea of a continuing ‘dementia epidemic’, but are now out of date because of changes in life expectancy, living conditions, and improvements in healthcare and lifestyle,” Professor Brayne said.

“The suggested decrease in dementia occurrence coincides with improvements in protective factors for dementia and a general reduction in risk factors, such as vascular disease, over recent decades,” she said.

The risk of developing dementia in later life is linked with cardiovascular disease, high-blood pressure, cholesterol levels and diabetes. It is also possible to protect against the degenerative brain disease with regular exercise, a healthy diet and mental activity such as doing crosswords and other puzzles.

“We are now potentially seeing the results of improvements in prevention and treatment of key cardiovascular risk factors such as high blood pressure and cholesterol reflected in the risk of developing dementia,” Professor Brayne said.

The study, published in The Lancet Neurology journal, found that in the UK there was an overall reduction of about 22 per cent in the prevalence of dementia in people aged 65 years in 2011 compared to the number predicted for that year back in 1990.

The results of a study carried out in Spain showed a significant decline in dementia prevalence in men aged 65 and older – by about 43 per cent – between 1987 and 1996.

The studies in the Netherlands and Sweden also showed a fall in the age-specific incidence of dementia, although these finding were not statistically significant.

Martin Prince, professor of epidemiological psychiatry at King’s College London, who was not involved in the research, said he would take a more guarded view of the study’s conclusions. “The suggestion dementia numbers could be stabilising in West European countries is only supported by one of the studies. This conclusion is therefore, in my view, somewhat speculative, and not reflective of the generality of the evidence,” Professor Prince said.

Tara Spires-Jones of the centre for cognitive and neural systems at Edinburgh University, said the study suggests the percentage of the population with dementia is not growing in the UK, and may actually have fallen slightly. “While this is good news, we have to keep in mind that our population, particularly of people over 85 who are at greatest risk, is growing, so the number of people with dementia is increasing overall,” Dr Spires-Jones said.

Moderate, regular exercise can boost the size of the parts of the brain that shrink with age, according to scientists who believe it could be one of the best ways of preventing senile dementia. Last year a study found that walking briskly for 30 to 40 minutes a day, three times a week was all that it takes to “re-grow” the structures of the brain linked with cognitive decline in later life. Taking statins – pills designed for people with heart conditions – is also reported to help.

Research has shown that while puzzles and crosswords may slow down the onset of dementia, people who do them may experience a quicker rate of decline once the condition does arrive.

Overall, Dr Laura Phipps of Alzheimer’s Research UK says a healthy lifestyle is the best bet – “eating a balanced, healthy diet, exercising regularly, not smoking, and keeping blood pressure and weight in check”.