It wouldn’t surprise many people to be told that poorer people are less healthy than their richer counterparts. It might surprise you to know that basic intelligence at adolescence, before adjusting for later education, produces a strong and significant trend. The higher the IQ, the lower the mortality, as if higher intelligence also means a ‘well-functioning body’. The sub-groups with strong trends also include suicide and accidents but not so much for cancer. The ‘actual’ IQ ranges for each of the groups is not given.
You will likely need a subscription to see the original, which is here: Batty et al. Epidemiology Volume 20(1), January 2009, pp 100-109.