Does training of general practitioners for intensive treatment of people with screen-detected diabetes have a spillover effect on mortality and cardiovascular morbidity in ‘at risk’ individuals with normoglycaemia? Results from the ADDITION-Denmark cluster-randomised controlled trial

AIMS/HYPOTHESIS: Within a trial of intensive treatment of people with screen-detected diabetes, we aimed to assess a potential spillover effect of the trial intervention on incident cardiovascular disease (CVD) and all-cause mortality among people who screened positive on a diabetes risk questionnaire but who were normoglycaemic. METHODS: In the Anglo–Danish–Dutch Study of Intensive Treatment In People with Screen-Detected Diabetes in Primary Care (ADDITION)-Denmark trial, 175 general practices were cluster-randomised into: (1) screening plus routine care of individuals with screen-detected diabetes (control group); or (2) screening plus training and support in intensive multifactorial treatment of individuals with screen-detected diabetes (intervention group). We identified all individuals who screened positive on a diabetes risk questionnaire in ADDITION-Denmark but were normoglycaemic following biochemical testing for use in this secondary analysis. After a median 8.9 years follow-up, we used data from national registers to compare rates of first CVD events and all-cause mortality in individuals in the routine care group with those in the intensive treatment group. RESULTS: In total, 21,513 individuals screened positive for high risk of diabetes but were normoglycaemic on biochemical testing in ADDITION-Denmark practices between 2001 and 2006 (10,289 in the routine care group and 11,224 in the intensive treatment group). During 9 years of follow-up, there were 3784 first CVD events and 1748 deaths. The incidence of CVD was lower among the intensive treatment group compared with the routine care group (HR 0.92 [95% CI 0.85, 0.99]). This association was stronger among individuals at highest CVD risk (heart SCORE ≥ 10; HR 0.85 [95% CI 0.75, 0.96]). There was no difference in mortality between the two treatment groups (HR 1.02 [95% CI 0.92, 1.14]). CONCLUSIONS/INTERPRETATION: Training of general practitioners to provide target-driven intensive management of blood glucose levels and other cardiovascular risk factors showed some evidence of a spillover effect on the risk of CVD over a 9 year period among individuals at high risk of diabetes. The effect was particularly pronounced among those at highest risk of CVD. There was no effect on mortality. TRIAL REGISTRATION: ClinicalTrials.gov NCT00237549