Between 1985 and 1988, all civil servants aged between 35 and 55 years in 20 departments in central London were invited to a medical examination at their workplace.20 21 With 73% participation, the cohort included 10 308 participants at entry to the study. At phase 3 in 1991-3, all participants known to be alive and in the country were invited to the screening clinic, which included an oral glucose tolerance test; 6058 men and 2758 women (85.5% of the original sample) attended. For this analysis, phase 3 (when an oral glucose tolerance test was done for the first time) serves as the baseline. Biochemical screening was repeated at phase 5 (1997-9) and phase 7 (2003-4). Additional questionnaire-only phases assessed diabetes status at phase 4 (1995-6) and phase 6 (2001). Of the baseline participants, 6156 participated in phase 7 screening, at which DNA was collected.
