Intelligence may contribute to health inequalities

Does IQ explain socioeconomic inequalities in health? Evidence from a population based cohort study in the west of Scotland BMJ Online First

Intelligence may play an important role in health inequalities, finds a study published online by the BMJ today.

Reducing socioeconomic inequalities in health is an important issue and the target of many governments. Understanding the causes of socioeconomic inequalities in health is crucial if effective interventions are to be identified.

One theory is that intelligence (IQ) might have a role in explaining these inequalities. This is based on evidence that low IQ scores are linked to higher rates of later death and disease, and IQ scores follow a social trend.

Researchers in Scotland tested the hypothesis that by taking account of IQ, the relation between socioeconomic position and health would disappear. Their study involved 1,347 men and women, aged 56 in 1987 and living in the West of Scotland. IQ was assessed by written test and socioeconomic position by interview. Over a 17 year period, the health of these men and women was monitored.

As expected, the poorest socioeconomic groups were at greatest risk of ill health and mortality. Taking account of IQ markedly reduced these effects. But, the risk of ill health in disadvantaged people was still at least twice that of advantaged people in half of the associations examined.

“Our findings indicate that IQ does not completely explain the health differences between rich and poor, but may contribute to them,” say the authors.

“The currently scant information about IQ and health needs to be enhanced, with empirical investigation of why IQ might predict health and how the links between low socioeconomic status, low IQ, and poor health might be broken,” they conclude.