title: Early insulin response and insulin sensitivity are equally important as predictors of glucose tolerance after correction for measurement errors.
abstract: 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.
authors.affiliation: Department of Public Health/Geriatrics, Uppsala University, Uppsala, Sweden. lars.berglund@ucr.uu.se
authors.forename: Lars
authors.initials: L
authors.lastname: Berglund
authors.forename: Christian
authors.initials: C
authors.lastname: Berne
authors.forename: Kurt
authors.initials: K
authors.lastname: Svärdsudd
authors.forename: Hans
authors.initials: H
authors.lastname: Garmo
authors.forename: Björn
authors.initials: B
authors.lastname: Zethelius
mesh_terms: 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
chemical_list: D001786:Blood Glucose; D005947:Glucose; D006442:Glycated Hemoglobin; D007328:Insulin