Edinburgh: People with higher intelligence test scores in childhood and early adulthood tend to live longer. This result has been found among every population that has been studied, says expert Ian Deary, Professor of Psychology, Centre for Cognitive Ageing and Cognitive Epidemiology, Department of Psychology, University of Edinburgh.
Indeed, the impact of intelligence on mortality rivals well-known risk factors for illness and death, such as high blood pressure, being overweight, high blood glucose, and high cholesterol. Its effect is almost as important as that of smoking.
Differences in human intelligence have environmental and genetic causes. An intelligence test score in early life is partly a record of what the environment has wrought on the brain and the rest of the body up to that time.
Babies who have lower birth weights, for example, are more prone to chronic illnesses later in life. They also have, on average, slightly lower intelligence. But tests of whether birth weight might explain some of the link between intelligence and mortality have found no connection.
Parents occupations are also related to their childs intelligence and later risk of illness: children from more privileged backgrounds tend to have higher intelligence and better health, and to live longer. However, there is no convincing evidence that parental background explains the link between higher intelligence and longer life.
Other researchers have viewed intelligence test scores as possibly more than just an indicator of an efficient brain. After all, the brain is just one organ of the body, so people whose brains work well in early life may also have other organs and systems that are more efficient than others.
But this system integrity idea is somewhat vague and difficult to test. The best we have done to date has been to examine whether peoples reaction speeds are related to intelligence and to mortality. They are.
Reaction-time tests involve little thinking, and merely ask people to respond as fast as they can to simple stimuli. People who react faster have, on average, higher intelligence scores and live longer.
A third potential explanation is that intelligence is about good decision-making. Every day, as we live our lives, we make decisions about our health: what, when, and how much to eat; how much exercise to take; how to look after ourselves if we have an illness; and so forth.
Therefore, the reason that intelligence and death are linked might be that people with higher intelligence in childhood make better decisions about health, and have healthier behaviours. As adults, they tend to have better diets, exercise more, gain less weight, have fewer hangovers, and so on.
So far, so good. But we do not yet have the full story. There have not been any studies with data on childhood intelligence, lots of subsequent data on adult health behaviours, and then a long-term follow-up for deaths. And only such a study could tell us whether it is these healthy behaviours that explain the link between intelligence and death.
A fourth type of explanation is that people with higher intelligence in childhood tend to attain better educational qualifications, work in more professional jobs, have higher incomes, and live in more affluent areas.
These variables are related to living longer, too. So, perhaps thats it: higher intelligence buys people into safer and more health-friendly environments.
Certainly, in some studies, social class in adulthood seems to explain a lot of the link between intelligence and death.
The problem is that this explanation is statistical. We are still not sure whether, say, education and occupation explain the effect of intelligence on health, or whether they are, in effect, merely surrogate measures of intelligence.
Researchers have also searched for clues about the intelligence-mortality link in specific types of death. This has been revealing. Lower intelligence in early life is associated with a greater likelihood of dying from, for example, cardiovascular disease, accidents, suicide, and homicide. The evidence for cancer is less certain. As we have come across these specific findings, we have realised that each link might need a different explanation.
Finally, we know that how intelligent we are and how long we shall live are caused by both environmental and genetic influences. There are experimental designs, using twins, that can find out the extent to which intelligence and mortality are linked because they share environmental and genetic influences.
Among the most informative exercises we can undertake in cognitive epidemiology is to obtain a large group of twins on whom there is data on early-life intelligence and who were tracked for a long time to find out who had died.
The ultimate aim of this research is to find out what intelligent people have and do that enables them to live longer. Once we know that, we will be able to share and apply that knowledge with the aim of achieving optimal health for all.
London: Research conducted by Help the Aged has revealed that the UK public rank mental decline higher than any other worry about ageing, including big issues like the pensions crisis and the fear of isolation (1).
In response to this concern, the Charity is today launching a new website www.disconnectedmind.org.uk to help mobilise public support for one of the worlds most promising scientific projects to combat the condition.
Help the Aged has committed to fund this historic project, called The Disconnected Mind, through to its conclusion in 2015. Donations are needed now to maximise the possibility of a breakthrough in the fight against early mental decline that usually leads to dementia (2).
The project is unique because the scientists leading the study at the University of Edinburgh will revisit 1,000 volunteers, who are now aged 71, who took part in the Scottish Mental Survey in 1947 a survey that has not been repeated since. The project will compare the participants childhood mental ability, current ability, biological health and 60 years of life experience.
www.disconnectedmind.org.uk uniquely divides the project into tangible pieces so that the public can see how any donation from them, however small, can make a big difference. For example, just £45 would fund the in-depth examination of one participants test results, which could hold the secret to the prevention or treatment of mental decline.
Early mental decline often leads to dementia that affects 700,000 people in the UK. Tragically, this is expected to rise to over a million by 2025 unless new ways are found to combat it.
More on the Survey
(1) Survey by GfK NOP for Help the Aged. A sample of 1000 adults aged 16+ in the UK were interviewed during the weekend of 4th 6th May 2007. This survey was designed to be nationally representative of the telephone owning population of the UK. It revealed that mental decline ranks higher (41% of responses) than any other concern about ageing, including big issues like the pensions crisis/lack of savings and fear of isolation. Initial mental decline often leads to full dementia which the survey revealed is the age-related health condition of greatest concern, with 53% of respondents ranking it above strokes, incontinence and osteoporosis.
(2) Four out of five people who experience mild mental impairment go on to develop dementia within six years.
The team of experts at the University of Edinburgh performing The Disconnected Mind project are Professor Ian Deary, Doctor John Starr, Professor Jim McCulloch, Professor Joanna Wardlaw, Professor Richard Morris and Doctor Karen Horsburgh.
Help the Aged is the charity fighting to free disadvantaged older people in the UK and overseas from poverty, isolation, neglect and ageism. It campaigns to raise public awareness of the issues affecting older people and to bring about policy change. The Charity delivers a range of services: information and advice, home support and community living, including international development work. These are supported by its paid-for services and fundraising activities – which aim to increase funding in the future to respond to the growing unmet needs of disadvantaged older people. Help the Aged also funds vital research into the health issues and experiences of older people to improve the quality of later life.