Prediabetes is associated with lower brain gray matter volume in the general population. The Study of Health in Pomerania (SHIP).

BACKGROUND AND AIMS: We investigated the associations of fasting (FG) and 2-h postload (2HG) plasma glucose from oral glucose tolerance test (OGTT) with gray (GMV) and white (WMV) matter volume.

METHODS AND RESULTS: We analyzed data from 1330 subjects without known diabetes mellitus, aged 21 to 81, from the second cohort (SHIP-Trend-0) of the population-based Study of Health in Pomerania (SHIP). Following the OGTT, individuals were classified in five groups (according to the American Diabetes Association criteria): normal glucose tolerance (NGT), isolated impaired fasting glucose (i-IFG), isolated impaired glucose tolerance (i-IGT), combined IFG and IGT (IFG + IGT) and unknown type 2 diabetes mellitus (UDM). GMV and WMV were determined by magnetic resonance imaging. FG, 2HG and OGTT groups were associated with GMV and WMV by linear regression models adjusted for confounders. FG and 2HG were inversely associated with GMV. The adjusted mean GMV, when compared with the NGT group (584 ml [95% CI: 581 to 587]), was significantly lower in the groups i-IFG (578 ml [95% CI: 573 to 582]; p = 0.035) and UDM (562 ml [95% CI: 551 to 573]; p < 0.001), but not different in the i-IGT (586 ml [95% CI: 576 to 596]; p = 0.688) and IFG + IGT (579 ml [95% CI: 571 to 586]; p = 0.209) groups. There were no associations of FG, 2HG and OGTT parameters with WMV.

CONCLUSION: Our findings suggest that elevated FG levels, even within the prediabetic range, might already have some harmful effects on GMV.