Washington D.C. [USA] : In a recent study, researchers have found that higher intelligence (IQ) in childhood is linked with a lower lifetime risk of major causes of death, including heart disease, smoking related cancers, respiratory disease and dementia.
This is regarded to be the largest study to date, which reports the causes of death in men and women across the life course.
The results suggest that lifestyle, especially tobacco smoking, is an important component in the effect of intelligence on differences in mortality.
Previous studies have shown that, on average, individuals with higher IQs tend to live a little longer than those with lower IQs, but these are largely based on data from male conscripts followed up only to middle adulthood.
A team of scientists examined the association between intelligence test scores measured at age 11 and leading causes of death in men and women up to age 79.
Their findings are based on data from 33,536 men and 32,229 women born in Scotland in 1936, who took a validated childhood intelligence test at age 11, and who could be linked to cause of death data up to December 2015.
Cause of death included coronary heart disease, stroke, specific cancers, respiratory disease, digestive disease, external causes (including suicide and death from injury), and dementia.
After taking account of several factors (confounders) that could have influenced the results, such as age, sex and socioeconomic status, the researchers found that higher childhood intelligence was associated with a lower risk of death until age 79.
For example, a higher test score was associated with a 28 percent reduced risk of death from respiratory disease, a 25 percent reduced risk of death from coronary heart disease, and a 24 percent reduced risk of death from stroke.
Other notable associations were seen for deaths from injury, smoking related cancers (particularly lung and stomach), digestive disease, and dementia.
There was no evident association between childhood intelligence and death from cancers not related to smoking.
They also point out that significant associations remained after further adjustment for smoking and socioeconomic status, suggesting that these factors did not fully account for mortality differences.
They believe that the future studies “would benefit from measures of the cumulative load of such risk factors over the life course.”
The team noted, “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. And they suggest that “tobacco smoking and its distribution along the socioeconomic spectrum could be of particular importance here.”
They concluded by saying, “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.”
The study was published in journal BMJ.