Summary: Findings reveal the relationships between socioeconomic status, brain size, and cognition are established early in life.
Source: University of Oslo
In a study of more than 50.000 participants, researchers from the Lifebrain consortium found that although more education and higher income tended to be associated with larger brain volumes and better cognitive scores, these associations varied considerably between groups studied.
For example, stronger relations between levels of socioeconomic status (education and income), brain volume and cognition were found in the US than European samples, suggesting that such relationships are not universal.
Further, the relationships seemed to be established early in life, during childhood brain development, and were not enhanced in adulthood. This suggests that socioeconomic status is unlikely to specifically protect the brain from effects of aging.
No uniform relationships found
There has been considerable focus on socioeconomic status as having an enhancing and potentially protective effect on the brain in aging. In the other end of the lifespan, socioeconomic factors are often assumed to have direct impact on brain development.
In this large, multi-national study, the first main finding was that although education and income in general were positively related to brain and cognitive function, no uniform relationships were observed.
Rather, whether a relationship was seen, and how strong this was, varied across sub-studies. This suggests that simple causality hardly governs the relationships between income, education and brain structure. This means that increasing education, for instance, will not automatically have a positive effect on brain health.
Links between socioeconomic status and the brain established in childhood
The researchers included two brain measures: intracranial volume and total brain gray matter volume. Intracranial volume changes very little after school-age, whereas gray matter volume can change throughout life.
The second key finding was that socioeconomic status was more strongly related to intracranial volume than to gray matter volume, suggesting that higher socioeconomic status does not seem to specifically protect the brain in aging.
Relationships between brain and cognitive measures in childhood and parents’ income and education were just as strong as relationships seen in adults. These finding suggest that relationships between socioeconomic status, brain and cognition are established early in life.
Lead author of the study and of the Lifebrain consortium, Kristine Walhovd, says;
“The way I see it, socioeconomic status is not likely to be primarily associated with less brain decline in ageing. Rather, it is associated with the development of bigger brains to begin with. But we do not know anything about causality. It could be other factors causing both.”
“Although the present results do not inform about the causes for the relationships, they stress the importance of early-life influences for understanding the brain through life”, says Walhovd.
The findings, including the significant variation of effects across cohorts, have implications for our understanding of whether, when and how socioeconomic status may impact brain and cognition.
About the Lifebrain consortium
This study is part of the EU-funded Lifebrain project. The major goal of the Lifebrain consortium is to ensure a fuller exploitation, harmonization and enrichment of some of the largest longitudinal studies of age differences in brain and cognition in Europe.
Education and Income Show Heterogeneous Relationships to Lifespan Brain and Cognitive Differences Across European and US Cohorts
Higher socio-economic status (SES) has been proposed to have facilitating and protective effects on brain and cognition. We ask whether relationships between SES, brain volumes and cognitive ability differ across cohorts, by age and national origin. European and US cohorts covering the lifespan were studied (4–97 years, N = 500 000; 54 000 w/brain imaging).
There was substantial heterogeneity across cohorts for all associations. Education was positively related to intracranial (ICV) and total gray matter (GM) volume. Income was related to ICV, but not GM.
We did not observe reliable differences in associations as a function of age. SES was more strongly related to brain and cognition in US than European cohorts. Sample representativity varies, and this study cannot identify mechanisms underlying differences in associations across cohorts.
Differences in neuroanatomical volumes partially explained SES–cognition relationships. SES was more strongly related to ICV than to GM, implying that SES–cognition relations in adulthood are less likely grounded in neuroprotective effects on GM volume in aging. The relatively stronger SES–ICV associations rather are compatible with SES–brain volume relationships being established early in life, as ICV stabilizes in childhood.
The findings underscore that SES has no uniform association with, or impact on, brain and cognition.