• F A Van de Laar, P L B J Lucassen, R P Akkermans, E H Van de Lisdonk, and W J C De Grauw.
• Radboud University Nijmegen Medical Centre, Department of General Practice, 229 HAG, P.O. Box 9101, Nijmegen, Netherlands. f.vandelaar@hag.umcn.nl
• Cochrane Db Syst Rev. 2006 Jan 1(4):CD005061.

BackgroundAlpha-glucosidase inhibitors (AGIs) reduce blood glucose levels and may thus prevent type 2 diabetes and cardiovascular disease in patients with impaired glucose tolerance. These possible effects, and the effects on quality of life, plasma lipids and body weight, have never been investigated in a systematic literature review and meta-analysis.ObjectivesTo assess the effects of alpha-glucosidase inhibitors in patients with impaired glucose tolerance (IGT) or impaired fasting blood glucose (IFBG), or both.Search StrategyWe searched The Cochrane Library (Clinical Trials database, formerly known as CENTRAL), PUBMED, EMBASE, Web of Science, LILACS, databases of ongoing trials, reference lists of relevant reviews, and we contacted experts and manufacturers. Date of last search was February 2006.Selection CriteriaRandomised controlled trials of at least one-year duration in patients with IGT or IFBG, or both, comparing AGI monotherapy with any other intervention.Data Collection And AnalysisTwo reviewers read all abstracts, assessed quality and extracted data independently. Discrepancies were resolved by consensus or by the judgement of a third reviewer.Main ResultsWe included five trials (2360 participants), all investigating acarbose, that included patients with IGT or patients 'at increased risk for diabetes' (n = 1). Study duration was one, three (n = 2), five and six years. One study was at low risk of bias and four studies at high risk of bias. Except for the outcome incidence of type 2 diabetes in acarbose versus no treatment (two studies), meta-analyses were not possible. Data from the study at low risk of bias suggests that acarbose decreases the occurrence of type 2 diabetes (NNT = 10), cardiovascular events (NNT = 50, based on 47 events, study not initially powered for this outcome), post-load blood glucose (-0.6 mmol/L, 95% CI -1.0 to -0.3) and body mass index (0.3 kg/m(2), 95% CI -0.1 to -0.5). No statistically significant effects were observed on mortality, other morbidity, glycated haemoglobin, fasting blood glucose, lipids and blood pressure. The effects on the incidence of type 2 diabetes were confirmed in two studies at high risk of bias (OR 0.2, 95% CI 0.1 to 0.6). Adverse effects were mostly of gastro-intestinal origin (OR 3.5, 95% CI 2.7 to 4.4).Authors' ConclusionsThere is evidence that acarbose reduces the incidence of type 2 diabetes in patients with IGT. However, it is unclear whether this should be seen as prevention, delay or masking of diabetes. Acarbose may prevent the occurrence of cardiovascular events, but this finding needs to be confirmed in more studies.

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