More intelligent, more dependable children live longer: a 55-year longitudinal study of a representative sample of the Scottish nation

The associations of childhood intelligence and dependability with adult mortality were examined in 1,181 people who were representative of the Scottish nation. Participants were born in 1936 and were followed for mortality from 1968 through early 2003. Higher intelligence and greater dependability were independent, significant predictors of lower mortality: With both factors entered together, the hazard ratio (HR) was 0.80 (95% confidence interval, CI: 0.65-0.99, p= .037) per standard deviation increase in intelligence and 0.77 (95% CI: 0.63-0.94, p= .009) per standard deviation increase in dependability. Children in the lower half of the distributions for intelligence and dependability were more than twice as likely to die compared with those who scored in the top half for both these measures (HR = 2.82; 95% CI: 1.81-4.41). Studied together for the first time in a representative sample, these two psychological variables are independent life-course risk factors for mortality. It is important to discover the mechanisms by which they influence survival.