Can Your IQ Influence Your Longevity?

Is there a relationship between intelligence and cardiovascular mortality?  This was the topic of a study of Vietnam War veterans by Scottish researchers that was published last year. The same group of researchers has now completed a similar analysis of data from the West of Scotland Twenty-07 Study, and published their findings in the European Journal of Cardiovascular Prevention and Rehabilitation.   

The study included 1,145 men and women who had IQ test scores, records of known cardiovascular risk factors, and 20-year follow-up for mortality.  Their average age at entry into the study was 56 in 1986-1987.

The top 5 most important predictors of cardiovascular mortality were:

Smoking - 5.58 hazard ratio (equivalent to the relative risk or likelihood in the higher vs. the lower smoking level).  

IQ – 3.76 (increased likelihood for lower vs. higher IQ subjects).

Income – 3.20 (increased likelihood for lower vs. higher income levels).

Systolic blood pressure: 2.61 (increased likelihood for higher vs. lower systolic BP).

Physical activity:  2.06 (increased likelihood for lower vs. higher level of activity).

For overall mortality a similar pattern was seen, with lower IQ in second place after heavier smoking in both cases. 

Before you attach too much significance to these findings, be aware that this study has been criticized by experts.  First, an ‘association’ in this type of study doesn’t prove ‘cause-and-effect’; a low IQ, per se, is not a cause of increased mortality.  Second, it seems very possible that the association of mortality with low IQ is ‘inescapably confounded’: this means that a lower IQ is generally accepted to go along with lower socio-economical status, lower access to medical care, and lower awareness of risk factors – all likely to be closely linked with increased mortality.  Corrections for these co-factors weren’t made in the study.  So don’t worry if you don’t do so well on IQ testing.  Just stop smoking, get plenty of exercise, and keep your blood pressure under control, and you’ll be as good as the rest – or better.