title: Trajectories of glycaemia, insulin sensitivity, and insulin secretion before diagnosis of type 2 diabetes: an analysis from the Whitehall II study.
abstract: BACKGROUND
  Little is known about the timing of changes in glucose metabolism before occurrence of type 2 diabetes. We aimed to characterise trajectories of fasting and postload glucose, insulin sensitivity, and insulin secretion in individuals who develop type 2 diabetes.
  
  
  METHODS
  We analysed data from our prospective occupational cohort study (Whitehall II study) of 6538 (71% male and 91% white) British civil servants without diabetes mellitus at baseline. During a median follow-up period of 9.7 years, 505 diabetes cases were diagnosed (49.1% on the basis of oral glucose tolerance test). We assessed retrospective trajectories of fasting and 2-h postload glucose, homoeostasis model assessment (HOMA) insulin sensitivity, and HOMA beta-cell function from up to 13 years before diabetes diagnosis (diabetic group) or at the end of follow-up (non-diabetics).
  
  
  RESULTS
  Multilevel models adjusted for age, sex, and ethnic origin confirmed that all metabolic measures followed linear trends in the group of non-diabetics (10,989 measurements), except for insulin secretion that did not change during follow-up. In the diabetic group (801 measurements), a linear increase in fasting glucose was followed by a steep quadratic increase (from 5.79 mmol/L to 7.40 mmol/L) starting 3 years before diagnosis of diabetes. 2-h postload glucose showed a rapid increase starting 3 years before diagnosis (from 7.60 mmol/L to 11.90 mmol/L), and HOMA insulin sensitivity decreased steeply during the 5 years before diagnosis (to 86.7%). HOMA beta-cell function increased between years 4 and 3 before diagnosis (from 85.0% to 92.6%) and then decreased until diagnosis (to 62.4%).
  
  
  CONCLUSIONS
  In this study, we show changes in glucose concentrations, insulin sensitivity, and insulin secretion as much as 3-6 years before diagnosis of diabetes. The description of biomarker trajectories leading to diabetes diagnosis could contribute to more-accurate risk prediction models that use repeated measures available for patients through regular check-ups.
  
  
  BACKGROUND
  Medical Research Council (UK); Economic and Social Research Council (UK); British Heart Foundation (UK); Health and Safety Executive (UK); Department of Health (UK); National Institute of Health (USA); Agency for Health Care Policy Research (USA); the John D and Catherine T MacArthur Foundation (USA); and Academy of Finland (Finland).
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, UK. a.tabak@ucl.ac.uk
authors.forename: Adam G
authors.initials: AG
authors.lastname: Tabák
authors.forename: Markus
authors.initials: M
authors.lastname: Jokela
authors.forename: Tasnime N
authors.initials: TN
authors.lastname: Akbaraly
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Brunner
authors.forename: Mika
authors.initials: M
authors.lastname: Kivimäki
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Witte
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology / Q000378:metabolism; D005215:Fasting; D005260:Female; D005951:Glucose Tolerance Test; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology; D050417:Insulin-Secreting Cells / Q000378:metabolism; D016014:Linear Models; D008131:London / Q000453:epidemiology; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D011236:Prediabetic State / Q000150:complications / Q000453:epidemiology / Q000378:metabolism; D011446:Prospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013997:Time Factors
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D007328:Insulin