We also considered a follow-up of at least two years on average because incidence of diabetes could alter approximately two years after modification of lifestyle.16 17 We extracted information in a standardised manner in duplicate, including baseline personal information such as body mass index, and duration of follow-up, exclusion criteria, sample size, loss to follow-up, assessments of beverage consumption and incident type 2 diabetes, types of beverage consumed, measures of prospective associations with 95% confidence intervals, covariates evaluated, and sources of funding.
We extracted measures of associations that were the most adjusted for sociodemographic and lifestyle factors, with and without further adjustment for adiposity measures.
We specifically aimed to meta-analyse the associations with and without adjustment for adiposity, because the association may be both mediated and confounded by this factor.
To provide policy relevant measures, we then used the result of the meta-analysis for sugar sweetened beverages to estimate the population attributable fraction for the 10 year risk of developing type 2 diabetes due to consumption of sugar sweetened beverages in contemporary populations of the United States and United Kingdom, where approximately half of each population in recent years consumed sugar sweetened beverages.1 10 Following the PRISMA guidelines15 and the protocol (not registered, available on request), we identified relevant studies through hand searches and systematic searches of four databases on (updated on 10 February 2014): Pub Med, Embase, Ovid, and Web of Knowledge.
In addition we contacted authors of cohorts that did not meet eligibility criteria but could be eligible on the provision of additional information (see supplementary table S1).
We examined risks of bias in concordance with the Cochrane tools, including a Cochrane risk of bias assessment tool for non-randomised studies of interventions.19 20 21 Seven domains were assessed: confounding, selection, exposure measurement, misclassification over time, missing data, outcome measurement, and selective reporting.
Statistical details are described in the supplementary information.