Study designs of evaluations included in the review
Randomised controlled trials (RCTs) of 2 years or more duration. Crossover trials were also considered but none of the trials lasted 2 years or more.
Specific interventions included in the review
Intensive insulin therapy (IIT) through multiple daily injections (3-4/day) of insulin or subcutaneous insulin pump, and conventional therapy (CT), defined as one or two insulin injections per day.
Participants included in the review
Adults (18-50 yrs) with type 1 diabetes. Studies involving type 1 diabetic patients after renal transplant were excluded.
Outcomes assessed in the review
The primary outcome measure was the number of major macrovascular events, including:
1. Cardiovascular disease (angina, myocardial infarction, angioplasty, coronary artery bypass grafting (CABG)).
2. Cerebrovascular disease (cerebrovascular accident).
3. Peripheral vascular disease (intermittent claudication, peripheral artery bypass).
4. Macrovascular death (fatal myocardial infarction, fatal cerebrovascular accident, sudden death).
Two or more events of the same type were counted as one; if a patient had different types of events, they were counted separately, even if they were within the same class. Data were also collected where available, on cardiovascular risk factors such as hypertension, lipids, smoking, body mass index (BMI) and insulin dose.
How were decisions on the relevance of primary studies made?
Abstracts were first reviewed, unblinded by one reviewer. Studies meeting the inclusion criteria were then subjected to full unblinded independent review by two reviewers. Agreement regarding study inclusion was evaluated by weighted Kappa with quadratic weights (Cichetti & Fleiss, 1977 see Other Publications of Related Interest no. 2). A minimum acceptable agreement was set a priori at a Kappa of 0.65. Disagreements were resolved by a third independent reviewer.