Does IQ vary systematically with all measures of socioeconomic status in a cohort of middle-aged, and older, men?

Abstract

Differences in IQ have been offered as an explanation for socioeconomic gradients in morbidity and mor-tality. Previous research has largely relied on linking education and conscription testing data with later life health. As this early life testing was used to determine a person’s academic path it is difficult to dis-entangle the effects of IQ from education. This study used IQ and socioeconomic status (SES) data col-lected concurrently in mid-life from men who did not experience IQ-test-driven career path direction in early life. If IQ is associated with SES generally then multiple domains of IQ it will be associated with all components of SES. In a subsample of men aged 35 - 80 (n = 287) from the Florey Adelaide Male Ageing Study, we evaluated relationships between each of four domains of cognitive ability (IQ domains): fluid (Gf); crystallised (Gc); visual/spatial (Gv) and processing speed (Gs). SES was measured as standardized education, income, occupational prestige and deprivation score. Age-adjusted linear regression was used to test each SES-z-score individually against each IQ domain. Then all four SES measures were included in a single model for each IQ domain. This study found that a panel of standard IQ tests were positively associated with attained education but not with income or area-level deprivation score. Two IQ abilities, Gf and Gc, were also associated with occupational prestige score. These associations suggest that lesser levels of health associated with lower socioeconomic status is not accounted for by a lesser innate ability and that intervention may be possible.