There have been many studies linking intelligence levels (IQ) recorded in childhood with living longer, showing that those with slightly higher IQs appear to live longer than those with slightly lower IQs, though the longest follow-up study has only previously gone up to middle age.

However, a new study published in the British Medical Journal has expanded on this with the first uniquely comprehensive follow-up – 68 years in this case – of childhood IQ in relation to not just longer living, but major causes of death. 

Researchers from the University of Edinburgh looked at the IQ test scores of more than 65,000 people who were born in Scotland in 1936 and had their IQ tested aged 11, and whose cause of death data was available in 2015, when the men and women had reached 79 years.

From the data available, they looked at “cause-specific mortality”, including from coronary heart disease, stroke, specific cancer types, respiratory disease, digestive disease, external causes, and dementia.

Their results corroborated previous studies, finding that those with a higher IQ recorded at age 11 were more likely to live until they were 79. More specifically, they found that higher childhood intelligence was associated with a lower risk of death from particular causes.

A higher test score meant a 28 percent lower risk of dying from respiratory disease, 25 percent reduced risk of death from coronary heart disease, and a 24 percent lower risk of death from stroke.

Higher IQ was also linked to lower risk of death from injury, dementia, digestive diseases, and cancer – particularly smoking-related ones such as lung and stomach. Their findings still stood after they had controlled for sex and socio-economic status.  

Interestingly, the hazard ratio for most causes of death was similar for both men and women, with the notable exception of higher IQ males having a 10 percent lower risk of death from dementia, compared to women who had a 24 percent lower risk.

The authors discuss their results and possible reasons for their findings in the study and an accompanying editorial also published in the BMJ. Theories include that those with higher IQs were more likely to know how to look after themselves, more likely to exercise, less likely to smoke, and more likely to visit a doctor if not well.

However, they do suggest that genetics plays a part as well and further investigation into the association between genes and IQ levels in relation to longevity of life need to be explored further.