A Longitudinal Perspective on the Implications of the Impaired Fasting Glucose Threshold for Identifying Individuals at Risk of Developing Type 2 Diabetes Mellitus

Abstract: Type 2 diabetes mellitus (T2DM) is a global health concern affecting six to ten percent of adults worldwide, with the number of diagnosed individuals projected to double in the next 25 years. However, effective public health strategies can help mitigate its impact on quality of life, morbidity, mortality and the associated social and economic burden. In Sweden, screening programs classify individuals with Impaired fasting glucose (IFG) as high-risk individuals, however scholars argue that preventative measures should also include those at lower fasting plasma glucose (FPG) concentrations as some evidence suggests that the disease begins developing several years before the current threshold. A systematic review and meta-analysis of cohort and case-control studies was conducted with the purpose of exploring the IFG threshold from a longitudinal perspective. Eleven studies on the incidence rates of T2DM in normoglycemic individuals and seven studies on pre-diagnostic trajectories of FPG concentrations were analyzed. Incidence rates increased progressively across the normoglycemic range, with a twelve-fold difference between the low and high end. FPG concentrations in eventual progressors and non-diabetic controls were significantly different twelve years prior to diagnosis. Mildly increasing FPG concentrations were observed in eventual progressors until three years before diagnosis, at which a larger increase followed. In the last year before diagnosis, FPG concentrations rose dramatically in this group. The findings imply that a lowering of the threshold would extend the time spent in the IFG state, allowing for earlier identification of at-risk individuals. In addition, further stratification of normoglycemic range may enhance the accuracy of T2DM risk assessment.