Early insulin response and insulin sensitivity are equally important as predictors of glucose tolerance after correction for measurement errors.
OBJECTIVE
We estimated measurement error (ME) corrected effects of insulin sensitivity (M/I), from euglycaemic insulin clamp, and insulin secretion, measured as early insulin response (EIR) from oral glucose tolerance test (OGTT), on fasting plasma glucose, HbA1c and type 2 diabetes longitudinally and cross-sectional.


METHODS
In a population-based study (n=1128 men) 17 men made replicate measurements to estimate ME at age 71 years. Effect of 1 SD decrease of predictors M/I and EIR on longitudinal response variables fasting plasma glucose (FPG) and HbA1c at follow-ups up to 11 years, were estimated using uncorrected and ME-corrected (with the regression calibration method) regression models.


RESULTS
Uncorrected effect on FPG at age 77 years was larger for M/I than for EIR (effect difference 0.10mmol/l, 95% CI 0.00;0.21), while ME-corrected effects were similar (0.02mmol/l, 95% CI -0.13;0.15mmol/l). EIR had greater ME-corrected impact than M/I on HbA1c at age 82 years (-0.11%, -0.28; -0.01%).


CONCLUSIONS
Due to higher ME effect of EIR on glycaemia is underestimated as compared with M/I. By correcting for ME valid estimates of relative contributions of insulin secretion and insulin sensitivity on glycaemia are obtained.
Berglund
Lars
L
Department of Public Health/Geriatrics, Uppsala University, Uppsala, Sweden. lars.berglund@ucr.uu.se
Berne
Christian
C
Svärdsudd
Kurt
K
Garmo
Hans
H
Zethelius
Björn
B
D000368:Aged; D000369:Aged, 80 and over; D001786:Blood Glucose / Q000032:analysis*; D002138:Calibration; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D005215:Fasting; D005260:Female; D005947:Glucose / Q000494:pharmacology; D005951:Glucose Tolerance Test / Q000592:standards; D006442:Glycated Hemoglobin / Q000378:metabolism; D006306:Health Surveys; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D001786:Blood Glucose; D005947:Glucose; D006442:Glycated Hemoglobin; D007328:Insulin