title: Is there a divergence in time trends in the prevalence of impaired glucose tolerance and diabetes? A systematic review in South Asian populations.
abstract: OBJECTIVE
  Recently, diabetes prevalence has increased in South Asians making it a global public health priority. There are suggestions that pre-diabetes, including impaired glucose tolerance (IGT), may not be increasing. We conducted a systematic review to explore the paradox. Research Design and Methods We searched electronic databases from inception to June 2009 for cross-sectional studies providing prevalence of pre-diabetes (using WHO criteria) in South Asian adult populations. Two reviewers independently screened articles, performed data extraction, quality appraisal and study classification with any discrepancies resolved by consensus. Repeated cross-sectional studies, categorized by pre-specified criteria, were used for the primary analysis, supplemented by analysis of comparable and all studies.
  
  
  RESULTS
  In total, 79 cross-sectional data sets (from 69 published studies) were identified resulting in the inclusion of 179 408 people. Four sets of repeated cross-sectional studies, conducted in Chennai, rural Tamil Nadu, Mauritius and Singapore (n = 30,399), provided time trend information. Three of them showed an increase in diabetes prevalence (P < 0.001) whereas IGT fell in two (P < 0.05), and was stable in the remainder. A similar pattern was seen among three other sets of comparable studies (n = 58,820) and in scatterplots of all 79 data sets.
  
  
  CONCLUSIONS
  This novel systematic review is the first to assess secular trends of pre-diabetes in any population. The data show diabetes prevalence is rising, whereas IGT prevalence is stable or falling. Explanations include: recent environmental or lifestyle changes favouring an increased rate of conversion from IGT to diabetes, or a cohort effect with improving maternal and infant nutrition resulting in reduced IGT with a fall in diabetes to follow.
authors.affiliation: Department of Public Health and Health Policy, NHS Lothian, Waverley Gate, Waterloo Place, Edinburgh. vkatikireddi@nhs.net
authors.forename: Srinivasa V
authors.initials: SV
authors.lastname: Katikireddi
authors.forename: Joanne R
authors.initials: JR
authors.lastname: Morling
authors.forename: Raj
authors.initials: R
authors.lastname: Bhopal
mesh_terms: D001211:Asia, Western / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000453:epidemiology* / Q000503:physiopathology; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test; D006801:Humans; D011236:Prediabetic State / Q000453:epidemiology; D015995:Prevalence
chemical_list: D005947:Glucose