The mediating effect of HbA1c levels on the relationship between education and cognitive function

Abstract

AbstractBackgroundHigher education has been shown to be positively associated with cognitive performance. However, the pathways, through which education is related to cognitive performance, have not been sufficiently explored. Higher levels of glycated hemoglobin (HbA1c) can lead to deterioration in cognitive performance. Part of the association with education may operate via the HbA1c level.MethodTo evaluate if the HbA1c level mediates the association of education with cognitive performance, we used longitudinal data from the Dutch Lifelines Cohort study (2006‐2015). Lifelines is a multi‐disciplinary prospective population‐based cohort study examining the health and health‐related behaviors of 167,729 persons living in the north of the Netherlands. The analyzed sample contained 19,878 persons observed at the baseline and the follow‐up, who were 50+ at baseline. We measured cognitive function using age‐standardized reaction time from the psychomotor function and attention tasks measured by the Cogstate Brief Battery at follow‐up. Higher reaction times indicate weaker cognitive function. The HbA1c level was measured at baseline by using participants’ blood samples. Linear Structural Equation Models were applied to estimate total, direct and indirect effects of education on cognitive function. We controlled for sex, age, income, physical activity, comorbidities and individual task accuracy.ResultHigher education was associated with faster reaction time respectively better cognitive performance (low: ref; middle: b = ‐0.125 p<0.01; high: b = ‐0.268 p<0.01). An increase in the HbA1c level (%) was associated with slower reaction time respectively poorer cognitive performance (b = 0.031 p = 0.02). Education had a significant effect on the HbA1c level (low: ref; middle: b = ‐0.023 p<0.01; high: b = ‐0.035 p<0.01). Most importantly, we found a significant indirect effect for education (low: ref; middle: b = ‐0.0007 p = 0.06; high: b = ‐0.001 p = 0.03) on cognitive function via the HbA1c level.ConclusionThe education effect of on cognitive performance was partially mediated by HbA1c levels. Early monitoring and regulation of blood glucose levels may be a potential prevention strategy to tackle cognitive impairments and mitigate the disadvantages in cognitive function of lower‐educated people.