Long-term effects of intensive multifactorial therapy in individuals with screen-detected type 2 diabetes in primary care: 10-year follow-up of the ADDITION-Europe cluster-randomised trial

BACKGROUND: The multicentre, international ADDITION-Europe study investigated the effect of promoting intensive treatment of multiple risk factors among people with screen-detected type 2 diabetes over 5 years. Here we report the results of a post-hoc 10-year follow-up analysis of ADDITION-Europe to establish whether differences in treatment and cardiovascular risk factors have been maintained and to assess effects on cardiovascular outcomes. METHODS: As previously described, general practices from four centres (Denmark, Cambridge [UK], Leicester [UK], and the Netherlands) were randomly assigned by computer-generated list to provide screening followed by routine care of diabetes, or screening followed by intensive multifactorial treatment. Population-based stepwise screening programmes among people aged 40-69 years (50-69 years in the Netherlands), between April, 2001, and December, 2006, identified patients with type 2 diabetes. Allocation was concealed from patients. Following the 5-year follow-up, no attempts were made to maintain differences in treatment between study groups. In this report, we did a post-hoc analysis of cardiovascular and renal outcomes over 10 years following randomisation, including a 5 years post-intervention follow-up. As in the original trial, the primary endpoint was a composite of first cardiovascular event, including cardiovascular mortality, cardiovascular morbidity (non-fatal myocardial infarction and non-fatal stroke), revascularisation, and non-traumatic amputation, up to Dec 31, 2014. Analyses were based on the intention-to-treat principle. ADDITION-Europe is registered with ClinicalTrials.gov, NCT00237549. FINDINGS: 343 general practices were randomly assigned to routine diabetes care (n=176) or intensive multifactorial treatment (n=167). 317 of these general practices (157 in the routine care group, 161 in the intensive treatment group) included eligible patients between April, 2001, and December, 2006. Of the 3233 individuals with screen-detected diabetes, 3057 agreed to participate (1379 in the routine care group, 1678 in the intensive treatment group), but at the 10-year follow-up 14 were lost to follow-up and 12 withdrew, leaving 3031 to enter 10-year follow-up analysis. Mean duration of follow-up was 9·61 years (SD 2·99). Sustained reductions over 10 years following diagnosis were apparent for bodyweight, HbA1c, blood pressure, and cholesterol in both study groups, but between-group differences identified at 1 and 5 years were attenuated at the 10-year follow-up. By 10 years, 443 participants had a first cardiovascular event and 465 died. There was no significant difference between groups in the incidence of the primary composite outcome (16·1 per 1000 person-years in the routine care group vs 14·3 per 1000 person-years in the intensive treatment group; hazard ratio [HR] 0·87, 95% CI 0·73-1·04; p=0·14) or all-cause mortality (15·6 vs 14·3 per 1000 person-years; HR 0·90, 0·76-1·07). INTERPRETATION: Sustained reductions in glycaemia and related cardiovascular risk factors over 10 years among people with screen-detected diabetes managed in primary care are achievable. The differences in prescribed treatment and cardiovascular risk factors in the 5 years following diagnosis were not maintained at 10 years, and the difference in cardiovascular events and mortality remained non-significant.