Dementia: G8 pledge welcome but it's up to us to stay healthy
The research is very clear: a healthy lifestyle will reduce the risk of dementia, says Peter Elwood
IN 1980 we set up a large long-term study of 2,500 men in Caerphilly, South Wales, to monitor their health habits and work out what five forms of healthy behaviour were integral to a disease-free life. We discovered that taking regular exercise, not smoking, a low body weight, healthy diet and low alcohol consumption were the main factors.
Our most recent finding, published in PLOS ONE, was that exercise in particular significantly reduced the risk of developing dementia. Men who had consistently followed four or five of these healthy forms of behaviour experienced a 60 per cent decline in dementia, as well as 70 per cent fewer instances of Type 2 diabetes, heart disease and stroke, compared with people who followed none.
While the protective effect of each separate healthy behaviour can easily be examined, what is far more informative is the relationships between combinations of these and the incidence of the various diseases. In the study, subjects who follow no healthy behaviour are used as a baseline, and from them we can monitor the effect it has on the likelihood of them developing disease (or for the purposes of the study, a reduction of disease incidence in others).
The major objectives of the study related to heart disease as this was, and still is, more common in men than in women (hence why only men were considered in the study). And every five years since the study began 35 years ago, we've questioned subjects in detail, recorded clinical details and taken blood samples. And every five years, details about new disease events (diabetes, heart attacks, stroke and cancer) were obtained from medical records.
More recently, detailed tests of cognitive function were performed and men who showed evidence of a decline were examined by a psycho-geriatrician (a psychiatrist specialising in treatment of the elderly) using further clinical tests for dementia.
And although only men were studied in Caerphilly, it was a representative population sample covering a wide number of different people, so we can confidently extrapolate the results for the rest of Wales. Other studies have also shown that the protective effects of lifestyle are closely similar in men and in women.
Consistency is most beneficial
Another interesting finding was that it's not just having healthy behaviour that's important but sticking to it. Subjects who, on repeated questioning, have given no evidence of serious changes appear to benefit the most from a reduction in disease. This was about half the subjects in the Caerphilly study (1023 men).
The impact of this is significant. Along with the reduction in dementia, diabetes and stroke, we also found that non-smoking was associated with a 40 per cent reduction in cancer, though this wasn't affected by other healthy behaviours.
Another way of evaluating these benefits is that although some men who consistently lived a full healthy lifestyle did get a vascular disease event, such as a heart attack, this occurred on average when they were up to about 12 years older than in men who followed no healthy behaviour. Similarly, we found death was postponed by about six years by a fully healthy lifestyle.
Yet another way of evaluating these data is to suppose that each man in the cohort had each been urged at the start of the study in 1980 to adopt just one additional healthy habit. If only half of them had complied, then over the 30 years, 12 per cent fewer would have developed diabetes; six per cent fewer would have had a vascular disease event; 13 per cent fewer would have developed dementia; and there would have been five per cent fewer deaths. This surely would be a reasonable target both for individual subjects, and for a community to take up an additional healthy behaviour and stick with it. When that behaviour has become a habit, take up another.
The other side of the coin, then, is most depressing. In 1980 we found less than one per cent of the subjects were following a lifestyle which included all five protective behaviours, and only a pathetic five per cent followed four. In 2009, a survey of 15,000 adult subjects in Wales showed that less than one per cent of adults were following all five behaviours and only seven per cent were following four. And this is despite the £280m a year spent promoting public health in Wales in recent years.
We know that maintaining a healthy lifestyle confers huge benefits in terms of disease reductions. And it is absolutely basic that the differences between the treatment of disease and the preservation of health is understood throughout the community.
We see prevention of bad health and disease as the responsibility of the individual - it's my decision whether I smoke or not, what body weight I maintain, whether or not I exercise regularly, what diet I take and how much I drink - but the irresponsibility burdens everyone.
It's great if the urgings of the prime minister and the discussions at the G8 conference leads to more funding for research, but let that not distract from the responsibility each of us has to live a healthier lifestyle.
Peter Elwood is an Honorary Professor of Medicine at Cardiff University and is funded by the Medical Research Council, Alzheimer's Society and the British Heart Foundation. This article was originally published at The Conversation.