Dementia is an increasing modern scourge. It has recently been reported to have overtaken coronary disease as the most frequent cause of death for women in the UK.
The two most common forms of dementia are Alzheimer’s disease (AD) and vascular dementia (VD). There are about 47 million people in the world living with dementia and this number is projected to rise to about 130 million by 2050. The figures for the UK are 850,000 rising to 2 million by 2050. This represents one in every 79 (1.3%) of the entire UK population and 1 in every 14 of the population aged 65 years and over.
Regular physical exercise and a high fitness level seem to reduce the risk of dementia or delay its onset. The Swedish Twin Registry study found that those who performed moderate exercise had one third the risk of developing dementia.
A recent Cochrane review (the best known source of summation of evidence based medicine) concluded that “The findings suggest that an exercise programme with components of both aerobic and resistance-type training, of at least moderate intensity and at least 45 min per session, on as many days of the week as possible, is beneficial to cognitive function in adults aged more than 50 years”. These are the Department of Health recommendations for exercise dose for health benefit for the population at large.
The Biobank survey (see Blog 2) has now added evidence about the effects of a healthy lifestyle on reducing the incidence of dementia in those with and without a genetic tendency to Alzheimer’s1.
In this particular study, nearly 200,000 people with a mean age of 64 were followed up for an average of eight years. Their genetic risk of developing dementia was assessed from a combination of genetic variants associated with Alzheimer’s disease. Their lifestyle was gauged as healthy or unhealthy from the responses to a questionnaire about smoking status, physical activity, diet and alcohol consumption.
An example of a healthy lifestyle included being a non-smoker, cycling or equivalent for two and a half hours per week, eating a balanced diet and drinking up to one pint of beer daily. An unhealthy lifestyle included being a smoker, taking no regular exercise, eating an unbalanced diet and drinking three pints of beer or more daily.
There was no link between genetic susceptibility to dementia and lifestyle. Those with the genetic susceptibility who had a healthy lifestyle had 60% the chance of developing Alzheimer’s of those with an unhealthy lifestyle – a highly significant difference.
It is very reassuring that a healthy lifestyle protects against Alzheimer’s disease. Nothing else seems to. The study does not identify the relative importance of each the four lifestyle elements but I am convinced that exercise was a large contributor.
The use of genetic information to identify individuals at high risk of particular diseases is growing. Proponents claim that knowledge of risk will lead to the adoption of behaviour designed to protect against such diseases but I am sceptical.
Smokers and excessive drinkers already know that they are harming themselves in all sorts of ways and this is also true of those who eat unhealthily. And everyone knows that exercise is good for them – will those who find out that they are risk of dementia start doing more? I would certainly like to think so but I am not so sure.
- doi: 10.1001/jama.2019.9879