We determined diabetes status on the basis of a 75 g oral glucose tolerance test (phases 3, 5, and 7), use of anti-diabetic drugs, or self report of a doctor’s diagnosis (phases 3 to 7). We defined diabetes by a two hour glucose of at least 11.1 mmol/l or fasting glucose of at least 7 mmol/l.27 Glycated haemoglobin (HbA1c) was measured at phase 7 in EDTA whole blood on a calibrated HPLC system with automated haemolysis before injection. HbA1 is resolved as a separate peak, which does not interfere with quantification of HbA1c.28 We calculated homoeostasis model assessment as (fasting glucose (mmol/l) × fasting insulin (mU/l)/22.5).29 Non-fasting participants (fasting less than five hours) were assigned a missing value (n=435, 9.1%).
