Fig. 1

Two-sample Mendelian randomisation results of the potential causal effect of lifetime smoking on type 2 diabetes. Results from the main IVW two-sample Mendelian randomisation (MR) analysis of lifetime smoking on type 2 diabetes and the sensitivity analysis results from MR Egger, SIMEX, weighted median, PRESSO and GSMR analyses. Results are the odds ratios (OR) of type 2 diabetes per 1 SD higher lifetime smoking index (LSI) score, with 95% confidence intervals (CI), noting that 1 SD higher LSI value is equivalent to an individual smoking 20 cigarettes per day for 15 years and stopping 17 years ago or smoking 60 cigarettes a day for 13 years and stopping 22 years ago. SNP single nucleotide polymorphism, IVW inverse-variance weighted, SIMEX simulation extrapolation, PRESSO pleiotropy RESidual sum and outlier, GSMR generalised summary-data-based Mendelian randomization.