Longitudinal examination of pancreatic β‐cell function in Japanese individuals

Aims/Introduction We carried out a retrospective, longitudinal analysis of β‐cell function between a diabetes mellitus group, including those that progressed to diabetes mellitus during the follow‐up period, and a diabetic type with glycated hemoglobin (HbA1c) <6.5 group, including those that progressed to a diabetic type during the follow‐up period. β‐Cell function was assessed using homeostasis model of assessment of β‐cell function. Materials and Methods The relationship between the duration of diabetes mellitus or the diabetic type and pancreatic β‐cell function was compared between the diabetes mellitus group (1,817) and diabetic type with HbA1c <6.5 group (1,843) using results from an oral glucose tolerance test. Linear mixed effects models were used to analyze repeated measurements of oral glucose tolerance tests. Results The slope of the regression line of β‐cell function for the duration of the diabetes mellitus group was −2.2%/year before the diagnosis. The slope differed after the diagnosis, and the difference was 1.3. The slope of the diabetic type group was −1.2%/year, and no significant difference was observed in the slope before and after the diagnosis. β‐Cell function at the onset was 54.3% in the diabetic type group and 40.6% in the diabetes mellitus group, and the slope of the regression line was significantly higher in the diabetes mellitus group. We divided the diabetes mellitus and diabetic type with HbA1c <6.5 groups into obese and non‐obese participants. β‐Cell function declined more with obesity. Conclusions Subsequent declines in β‐cell function were faster in the diabetes mellitus group than that in the diabetic type with HbA1c <6.5 group, and increased with obesity.