Longitudinal Examination of Links Between Risk Factors for the Metabolic Syndrome and Both Age and Fasting Glucose Levels in Nondiabetic Subjects

Abstract

ABSTRACTBackground: Previous evaluations in nondiabetic subjects revealed statistically significant correlations between fasting blood glucose (FBG) levels used as an estimate of insulin resistance and many components constituting the metabolic syndrome. Similar significant correlations were not found employing chronological age as the independent variable in the same nondiabetic individuals.Objective: The major purpose here was to replicate as well as corroborate the previous cross-sectional observations, emphasizing results obtained from data collected longitudinally.Methods: Material was assessed from 99 nondiabetic volunteers who had undergone 2 separate baseline measurements carried out over a minimum of 5 and up to a maximum of 20 years.Results: Findings from the starting baseline measurements mimicked many observations perceived in the earlier published cross-sectional material. The following correlations with elements constituting the metabolic syndrome using FBG as an independent variable were once more statistically significantly positive: scale weight, fat mass, circulating levels of triglycerides and high-sensitivity C-reactive protein (hsCRP). High-density lipoprotein (HDL) cholesterol was once again appropriately significant in a negative direction. In contrast, the same correlations were generally nonsignificant when age replaced FBG as the independent variable. Examining the 2 data sets over the 5–20-year intervals, FBG increased statistically significantly over time. However, the average increase clinically was relatively minor: −92.1 mg/dL ± 1.1 (SEM) vs 95.1 mg/dL ± 1.1 (SEM), p < 0.007. When the actual changes (delta) in the dependent parameters were correlated with the individual passages of time (intervals in years), only downward changes in aspartate aminotransferase (AST) levels were statistically significant. Fat-free mass showed a trend downward, whereas fat mass, trunk fat, and triglycerides merely demonstrated trends upward.Conclusion: Current findings gathered over years are consistent with the original hypothesis that maintaining relatively low, stable circulating glucose levels during aging retards the development and intensity of many common manifestations of the metabolic syndrome.