ESPE Yearbook of Paediatric Endocrinology

Diabetes Care. 2021 Apr 26:dc202308. doi: 10.2337/dc20-2308. PMID: 33905344.

In brief: The multicenter SEARCH for Diabetes in Youth Study assessed cognitive function in adolescents and young adults with type 1 diabetes mellitus (T1DM) (n=1095) or T2DM (n=285). Mean age was 21.6±5.1 years and mean diabetes duration 11.0±3.4 years. Having T2DM was associated with lower fluid cognitive scores before adjustment for confounders. However, this association was attenuated to non-significance with the model inclusion of a priori confounders and the sub-domain of crystallized cognition scores. In a final combined model, receptive language, waist-to-height ratio and depressive symptoms remained significantly different between groups.

Comment: Intelligence is composed of various interacting abilities. The concepts of fluid and crystallized intelligence were first proposed by Cattell (1), who defined fluid cognition as “the ability to perceive relationships independent of previous specific practice or instruction concerning those relationships.” An example of fluid intelligence is puzzle solving. By contrast, crystallized intelligence involves knowledge that comes from prior learning and past experiences, for example reading comprehension and vocabulary tests.

This study assessed subdomains of cognition in adolescents with T2DM or T1DM, compared to the general population. Subdomains of fluid cognition included: cognitive flexibility, working and episodic memory, processing speed and attention/inhibitory control. Subdomains of crystallized cognition included receptive language (Picture Vocabulary Test).

Adolescents with T2DM performed below the national average in fluid cognition. Both the T2DM and T1DM groups performed below the national average with respect to inhibitory control and sustained attention scores. In models unadjusted for covariates, the T2DM group performed significantly worse than the T1DM group in fluid cognition. However, in models that included potential confounders (sex, race/ethnicity, parental education, household income, duration of diabetes, obesity, depression, hypoglycaemic events in the past year and glycaemic control) and also receptive language (crystallized cognition), fluid cognition did not differ between the groups. Receptive language, waist-to-height ratio and depressive symptoms remained significantly different between T2DM and T1DM.

Obesity and depression per se appear to be associated with additional sequelae. Lower fluid intelligence in adolescents has been associated with physical violence (both in the role of victim and victimizer), drug intake and lower self-esteem (2). Together, these emphasize the importance of programs for early diagnosis of depression and prevention of obesity.

Reference: 1. Brown RE. Hebb and Cattell: The Genesis of the Theory of Fluid and Crystallized Intelligence. Front Hum Neurosci. 2016; 15;10:606. doi: 10.3389/fnhum.2016.00606. PMID: 28018191.2. Huepe D, et al. Fluid intelligence and psychosocial outcome: from logical problem solving to social adaptation. PLoS One. 2011;6(9):e24858. doi: 10.1371/journal.pone.0024858. PMID: 21957464.