The company says the study was based on a summaryof separate studies, when the proper way to determine the drug's effects is to conduct long-term clinical trials of patients taking Avandia.
Significantly, UpToDate generally offers not just a summaryof recommendations but also an explanation of the associated physiology and a review of relevant clinical studies.
For an objective summaryof the evidence, see the articles by neurologist Steven Novella here and here, which summarize a dozen epidemiological studies.