title: Age trajectories of glycaemic traits in non-diabetic South Asian and white individuals: the Whitehall II cohort study.
abstract: OBJECTIVE
  South Asian individuals have an increased prevalence of type 2 diabetes, but little is known about the development of glycaemic traits in this ethnic group. We compared age-related changes in glycaemic traits between non-diabetic South Asian and white participants.
  
  
  METHODS
  In a prospective British occupational cohort with 5-yearly clinical examinations (n = 230/5,749 South Asian/white participants, age 39-79 years at baseline), age-related trajectories of fasting glucose (FG) and 2 h post-load glucose (PLG), log-transformed fasting insulin (FINS) and 2 h post-load insulin (PLINS), HOMA insulin sensitivity (HOMA2-%S) and HOMA insulin secretion (HOMA2-%B) were fitted for South Asian and white individuals who remained free of diabetes between 1991 and 2009.
  
  
  RESULTS
  In sex-adjusted multilevel models, FG was stable in white participants but increased with age in South Asians (0.12 [SE = 0.04] mmol/l per decade). PLG, FINS and PLINS levels were lower among white participants (by 0.271 [SE = 0.092] mmol/l, 0.306 [SE = 0.046] log pmol/l, 0.707 [SE = 0.059] log pmol/l at age 50, respectively) compared with South Asians, although their age-related trajectories were parallel. HOMA2-%S was higher (0.226 [SE = 0.038] at age 50) and HOMA2-%B lower (by 0.189 [SE = 0.026] at age 50) among white than South Asian participants. The age-related decline in HOMA2-%S was similar in these groups, but the age-related increase in HOMA2-%B was greater in white participants (0.04 [SE = 0.02] per decade). This difference was explained by obesity, lifestyle and social status.
  
  
  CONCLUSIONS
  Findings from a diabetes-free population suggest an inadequate pancreatic beta cell reserve in South Asians, as a significantly steeper age-related increase in FG was observed in this ethnic group compared with white individuals.
authors.affiliation: Department of Epidemiology and Public Health, University College London, 1-19 Torrington Place, London, WC1E 6BT, UK.
authors.forename: Satoyo
authors.initials: S
authors.lastname: Ikehara
authors.forename: Adam G
authors.initials: AG
authors.lastname: Tabák
authors.forename: Tasnime N
authors.initials: TN
authors.lastname: Akbaraly
authors.forename: Adam
authors.initials: A
authors.lastname: Hulmán
authors.forename: Mika
authors.initials: M
authors.lastname: Kivimäki
authors.forename: Nita G
authors.initials: NG
authors.lastname: Forouhi
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Iso
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Brunner
mesh_terms: D000328:Adult; D000368:Aged; D001208:Asia; D001786:Blood Glucose / Q000378:metabolism; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies
chemical_list: D001786:Blood Glucose; D007328:Insulin