Introduction
In the Anglo-Danish-Dutch study of Intensive Treatment in People with Screen-Detected Diabetes in Primary care (ADDITION) study, 300 000 individuals with a high risk of type 2 diabetes were screened for type 2 diabetes, according to WHO 1999 criteria.1 2 Subsequently, in more than 3000 screen-detected patients, the effect of an intensive multifactorial treatment (IT) was compared with routine care (RC), according to national guidelines.3 After 5 years, a reduction in fatal and non-fatal cardiovascular disease (CVD) of 17% (n.s.) was found in favor of the IT group. A remarkable result was the finding that 5 years after screen detection, 37% and 45% of the participants with type 2 diabetes in the IT and RC groups did not use any glucose-lowering medication.3 After 5 years, the intervention stopped, and the subsequent treatment intensity was up to the general practitioner and the patient.
Results of two recent post hoc analysis with the ADDITION Denmark screening data indicated that after a follow-up of approximately 10 years people diagnosed after population-based screening had a 21% significant lower risk on all-cause mortality and a 16% significant lower risk on CVD events, but no significant risk reduction on CVD mortality compared with unscreened controls.4 5 Overall, there was little benefit that could be directly related to the screening programme. In part, this was due to the high degree of opportunistic screening in the control group. Based on these results, it was suggested that if opportunistic screening has been well established in a healthcare system, population-based screening might not add additional health benefits.4 5 In the Netherlands, since two decades, general practitioners are recommended to screen people with a high risk on type 2 diabetes, during surgery hours.6 This opportunistic screening is likely established differentially across general practices.7
Targeted population-based screening as well as opportunistic screening detect people with type 2 diabetes relatively early in the course of their disease. At that time most of them will be asymptomatic. Although evidence is available that early detection is beneficial for disease control, the impact of population-based screening compared with care-as-usual (including not fully implemented opportunistic screening) needs to be explored.
With increased duration of type 2 diabetes, most people have a growing need of glucose-lowering medication and eventually require insulin.8 9 According to a computer-simulated model based on the ADDITION data, it is speculated that the number of people on insulin therapy would be much higher if they were diagnosed during care-as-usual, an estimated (lead time of) 3–6 years later.10 Moreover, presumptive evidence is reported that early treatment of hyperglycemia will postpone the indication for insulin treatment due to possible effects on β-cell function.11–13
Hence, we hypothesize that, irrespective of age at diagnosis, on the long run, the need for insulin therapy is less in people diagnosed with type 2 diabetes during targeted population-based screening (like in the ADDITION study) compared with people with diabetes diagnosed during care-as-usual. Therefore, we evaluated insulin prescription and glycemic control in Dutch participants from the ADDITION study (both IT and RC) 10 years after being diagnosed with type 2 diabetes. We compared these results with data from Dutch people with a known diabetes duration of 7 years (assuming a lead time of 3 years) and 10 years (since the exact lead time is unknown) from two ‘care-as-usual’ diabetes cohorts (Groningen Initiative to Analyze Type 2 Diabetes Treatment (GIANTT) and Zwolle Outpatient Diabetes project Integrating Available Care (ZODIAC)).14 15