IQ in early adulthood, socioeconomic position, and unintentional injury mortality by middle age: a cohort study of more than 1 million Swedish men.
The authors evaluated the little-examined association between intelligence (IQ) and injury mortality and, for the first known time, explored the extent to which IQ might explain established socioeconomic inequalities in injury mortality. A nationwide cohort of 1,116,442 Swedish men who underwent IQ testing at about 18 years of age was followed for mortality experience for an average of 22.6 years. In age-adjusted analyses in which IQ scores were classified into 4 groups, relative to the highest scoring category, the hazard ratio in the lowest was elevated for all injury types: poisonings (hazard ratio (HR) = 5.82, 95% confidence interval (CI): 4.25, 7.97), fire (HR = 4.39, 95% CI: 2.51, 7.77), falls (HR = 3.17, 95% CI: 2.19, 4.59), drowning (HR = 3.16, 95% CI: 1.85, 5.39), and road injury (HR = 2.17, 95% CI: 1.91, 2.47). Dose-response effects across the full IQ range were evident (P-trend < 0.001). Control for potential covariates, including socioeconomic position, had little impact on these gradients. When socioeconomic disadvantage -- indexed by parental and subject's own occupational social class -- was the exposure of interest, IQ explained a sizable portion (19%-86%) of the relation with injury mortality. These findings suggest that IQ may have an important role both in the etiology of injuries and in explaining socioeconomic inequalities in injury mortality.
Batty
G David
GD
MRC Social and Public Health Sciences Unit, University of Glasgow, Glasgow, UK.
Gale
Catharine R
CR
Tynelius
Per
P
Deary
Ian J
IJ
Rasmussen
Finn
F
D000059:Accidents / Q000401:mortality* / Q000523:psychology*; D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D006304:Health Status; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D012959:Socioeconomic Factors; D013548:Sweden / Q000453:epidemiology; D014947:Wounds and Injuries / Q000209:etiology / Q000401:mortality* / Q000523:psychology*; D055815:Young Adult