Study: Smarter People Live Longer

The World Health Organisation defines life expectancy as "the average number of years a person is expected to live on the basis of the current mortality rates and prevalence distribution of health states in a population." Statistics released by the Union Ministry of Health and Family Welfare show that life expectancy in India has gone up by five years, from 62.3 years for males and 63.9 years for females in 2001-2005 to 67.3 years and 69.6 years respectively in 2011-2015. Experts attribute this jump - higher than that in the previous decade to better immunization and nutrition, coupled with better prevention and treatment of infectious diseases.

A more surprising discovery is that there is a strong link between mortality and IQ. Higher intelligence means, on average, a longer life. Smarter people are also healthier. This relationship has been extensively documented by Ian Deary and his colleagues at the University of Edinburgh using data from the Scottish Mental Surveys.

"Childhood intelligence was inversely associated with all major causes of death," reports the research team, led by University of Edinburgh psychologist Catherine Calvin. The study showed that children with higher IQ experience a lower lifetime risk of major causes of death, including heart disease, stroke, smoking related cancers, respiratory disease and dementia.

Further, lifestyle, especially tobacco smoking, can be an important component in the effect of intelligence on differences in mortality, the researchers said.

The link between IQ and mortality has been replicated in more than 20 longitudinal studies from around the world, and has given rise to the field of cognitive epidemiology, which focuses on understanding the relationship between cognitive functioning and health. The study, published in The BMJ, confirms it in two important ways. It traces its subjects all the way to age 79, and finds the apparent protective effect of intelligence continues far into old age.

Furthermore, it finds that the differences in mortality rates cannot be attributed entirely to the fact that intelligent people are less likely to smoke, and tend to enjoy a higher economic status. While those factors play a major role, they aren't the entire story.

The study featured data on 33,536 men and 32,229 women, all of whom were born in Scotland in 1936, and completed a standard intelligence test in 1947, at age 11. The test featured 71 items "tapping verbal and non-verbal reasoning ability."

The researchers followed them for 68 years, noting who had died, at what age, and of what cause. The results were striking: a 15-point IQ advantage translated into a 21% greater chance of survival. For example, a person with an IQ of 115 was 21% more likely to be alive at age 76 than a person with an IQ of 100 (the average for the general population).

"The study confirms that intelligence test scores in childhood are significantly associated with subsequent mortality. More importantly, it shows that childhood IQ is strongly associated with causes of death that are, to a great extent, dependent on already known risk factors," said Daniel Falkstedt, Assistant Professor at the Karolinska Institutet in Sweden.

"Tobacco smoking and its distribution along the socioeconomic spectrum could be of particular importance here. It remains to be seen if this is the full story or if IQ signals something deeper, and possibly genetic, in its relation to longevity," Falkstedt added.

Another hypothesis is that a high IQ signifies a sturdy constitution and a body that's going to last - it's essentially a signifier rather than a cause, some scientists believe. One study published in 2005 found that better reaction times specifically helped people live longer - so a high IQ is possibly an indication of an efficient nervous system, rather than being itself a cause of longer life, the researchers proposed.

Alternatively, or perhaps in addition to the above suggestions, it could be that genes are contributing to the link between IQ and longevity.

It's a complicated area of science, particularly as an IQ score doesn't necessarily directly represent intelligence, and can be affected by social class, education standards, and other cultural factors - if you're preconditioned to think you'll do badly in an exam, for example. Nevertheless, the link is there, rest assured, high-school brainiacs. You may be mocked as nerds today, but you'll probably live longer than your C-plus peers.