The differences in results may reflect, in part, the use of different exposure cut points.
Use of different exposure categories makes summarising the published literature problematic, particularly for duration of use.
Of the 20 studies with 22 risk estimates included in our systematic review, we excluded six estimates for the purpose of meta-analysis: four estimates for lack of sufficient information (16, 23, 26, 28) and two for use of different exposure or outcome definitions from other included studies (15, 19).
Results from five studies provided sufficient data for meta-analysis, using three studies for each analysis, with one study used in two meta-analyses of different exposures.
We have attempted to remove the effects of different exposures by using the number of events per 100 or per 1000 patient years as a standard, with annualised rates justified by the observation of constant gastrointestinal and cardiovascular risk in large randomised studies [ 13, 15, 27].
This study also examined the risk of HL using a number of different exposure classification methods, raising the issue of multiple testing.
Table 2 summarizes the results from comparisons of different exposure models using different ranking weights for intensity (Peters et al., 2011).
The presentations included the characteristics (glucose variability) and use of different glycaemic exposure markers.
The use of two different lamps for the acquisitions (first the saturated metallic iodide lamp, then the halogen or incandescence lamp) is preferable both to the use of two different exposure levels for the metallic iodide lamp, and to a double acquisition with one of the broad spectrum lamps.
Nevertheless, the fact that associations between Cd and effects on bone were observed by the use of three different exposure assessment methods (urine, blood, and dietary intake) reduces the likelihood that the results were due to confounding.
