In their report van Oort and others¹ clearly describe and empirically examine the potential mediating factors—broadly categorised by the authors as material, psychosocial, and behavioural—that might account for the well established inverse education-mortality gradient. We believe the role of intelligence (denoted here as IQ, and defined as a person’s ability to learn, reason, and solve problems²) warrants mention, given its link with all cause mortality, other somatic health outcomes, and at least two (material and behavioural factors) of the aforementioned pathways.³

Recently reported findings from a series of cohort studies show an inverse association between IQ, assessed using psychometric tests, and later death, whether this “exposure” was quantified in childhood, early adulthood, middle age, or older age.³ Although fewer data are available for cause specific outcomes, similar gradients have also been reported for childhood assessed IQ in relation to adult risk of ischaemic heart …