Comparison of the relationship of age and beta cell function in three ethnic groups

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Abstract
Prevalence of type 2 diabetes and glucose intolerance increase with age. It has been demonstrated that beta cell function declines at about 1% per year in glucose tolerant Caucasians. However, this relationship is not known to exist in other ethnic groups. We investigated the relationship of age to beta cell function (%B) and insulin sensitivity (%S), estimated by the homeostasis model assessment, in a nationally representative sample of healthy US adults who participated in a cross-sectional study, the third National Health and Nutrition Examination Survey. Only those subjects who had never been told to have diabetes by a physician, with HbA1C < 6% and fasting plasma glucose concentration < 5.56 mmol/l with proper fasting glucose and insulin concentration were included in this analysis (560 non-Hispanic whites, 231 non-Hispanic blacks and 298 Hispanics). Age was positively correlated to HbA1C and fasting glucose concentration, but it was negatively correlated to %B in all three ethnic groups. In contrast, ageing had no influence on %S in all three ethnic groups. Pair-wise comparison showed age had a similar influence among three ethnic groups on fasting glucose concentration, HbA1C and %B, respectively. Multivariate analysis confirmed an independent influence of age on fasting glucose concentration, HbA1C and %B among three ethnic groups. We observed %B declines at about 1% per year among all three ethnic groups. The age-related rising fasting plasma glucose concentration and HbA1C is most likely a consequence of age-related decline in beta cell function.