Identification of factors differentially associated with isolated impaired fasting glucose and isolated post-load impaired glucose tolerance: the Hong Kong Cardiovascular Risk Factor Study

Abstract

Background: The use of fasting and post-prandial glucose levels in the classification of hyperglycaemic states often identifies distinct subjects, but the factors determining these intermediate-isolated glucose intolerant states are yet to be clearly elucidated in Chinese subjects. Methods: Representative subjects (nZ2769) were randomly recruited from the Hong Kong Chinese population and glycaemic status was determined using both fasting and 2h 75 g oral glucose tolerance test glucose levels. The relationship between the groups with isolated glucose intolerance and vascular risk factors was investigated using ANOVA and logistic regression analyses. Results: Using either criterion, diabetes was identified in 265 (9.6%) subjects and glucose intolerance in 568 (20.5%) subjects. Of those 568, isolated impaired glucose tolerance (IGT) using the post-load criterion was identified in 49.5% and isolated impaired fasting glucose (IFG) in 30.5%. Ageing and hyperinsulinaemia were common determinants of IGT and IFG; with small hip circumference a marker of poorer early life development and being born in China rather than Hong Kong, a possible low birth weight marker was also associated with IFG. Hypertension, hypertriglyceridaemia and poor education were also associated with IGT. When we looked for factors differentially associated with these glucose intolerant states, female sex, greater hip circumference, high triglyceride levels, low fasting insulin levels, and not being born in China were independently associated with isolated IGT compared with isolated IFG. Conclusion: Despite common antecedents to the glucose intolerant states, isolated IFG appeared to be particularly associated with early life development, and isolated IGT was more strongly associated with obesity-related determinants such as hypertriglyceridaemia.

Sleep-Disordered Breathing and Impaired Glucose Metabolism in Normal-Weight and Overweight/Obese Individuals

“…The unadjusted odds ratio for IFG was approximately twice as great in individuals with SDB compared with those without SDB. Although this association was much attenuated in adjusted analyses of data obtained in the entire analytic sample and in the overweight subgroup, the 60% increased odds of IFG observed in adjusted analyses performed in the nonoverweight subgroup suggest that normal-weight individuals with SDB are at an increased risk for experiencing defects in early insulin secretion and increased endogenous glucose output (34).…”

“…Our data also extend prior work by characterizing the association between specific indexes of IGM with SDB. Recent research (33) comparing the new revised definition of IFG (FPG Ն100 mg/dl) with IGT indicates that IFG and IGT may identify distinct groups, with different background risks (34,35). The unadjusted odds ratio for IFG was approximately twice as great in individuals with SDB compared with those without SDB.…”

“…Isolated IGT, reported commonly in the setting of central obesity and considered to be a measure of peripheral insulin resistance (13,22,34), was also more prevalent in individuals with SDB. After adjusting for BMI and waist circumference, the differences in prevalence between the SDB and non-SDB group was quite modest, however, especially in overweight/obese subjects.…”

“…The potential clinical importance of this association relates to data that suggest that this category of IGM reflects more profound abnormalities in insulin action, insulin secretion, and endogenous glucose output when compared with abnormalities in either IFG or IGT alone (13,22). Individuals with combined abnormalities have been shown to be at higher risk for an unfavorable cardiovascular risk profile, rapid development of diabetes, and premature death, compared with individuals with isolated IFG or IGT (12,13,22,34,35). The high unadjusted prevalence (18.3%) of combined glucose intolerance (IFG plus IGT) and occult diabetes (13.7%) found in the overall SDB group suggest that individuals with SDB are at special risk for diabetes and its cardiovascular complications, underscoring the need for further research addressing strategies for reducing the health risks in this population.…”

“…The participants' demographic characteristics, especially older age and predominantly Caucasian race, limits generalizability to younger groups or to ethnic minorities. As aging was reported as a common determinant of IFG or IGT (34), and the median age for all SDB groups was higher compared with the non-SDB groups, there is a possibility of residual confounding by age, although this is unlikely, as the extensive overlap in age distribution between groups should allow effect adjustment for age in multivariable models. Despite adjustment for both BMI and waist girth, some degree of residual confounding from differences in visceral fat, which was not directly measured, remains possible.…”