A unique study looking at the difference in cardiovascular disease (heart disease and stroke) and life expectancy between people of high and low socio-economic status has found that a person’s IQ may have a role to play. Researchers analyzed data from a group of 4,289 former soldiers in the USA. They found that IQ explained more than 20% of the difference in mortality between people from socio-economically disadvantaged backgrounds compared to those from more advantaged backgrounds.