Diabetes mellitus is now seen as a progressive disorder of glucose metabolism, affecting about 5% of the population worldwide, over 85% of whom have type 2 diabetes. Type 2 diabetes may occur with obesity, hypertension and dyslipidaemia (the metabolic syndrome), which are powerful predictors of CVD. Blood glucose levels rise progressively over time in people with type 2 diabetes regardless of treatment, causing microvascular and macrovascular complications.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical question: What are the effects of interventions in adults with type 2 diabetes? We searched: Medline, Embase, The Cochrane Library and other important databases up to October 2006 (BMJ Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
We found 69 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
In this systematic review we present information relating to the effectiveness and safety of the following interventions: combined oral drug treatment, diet, education, insulin (continuous subcutaneous infusion), insulin, intensive treatment programmes, meglitinides (nateglinide, repaglinide), metformin, monotherapy, blood glucose self-monitoring (different frequencies), and sulphonylureas (newer or older).
Diabetes mellitus is now seen as a progressive disorder of glucose metabolism; it affects about 5% of the population worldwide, over 85% of whom have type 2 diabetes.
Type 2 diabetes is often associated with obesity, hypertension, and dyslipidaemia (the metabolic syndrome), which are powerful predictors of CVD.Type 2 diabetes is a disease in which glucose levels rise over time, with or without treatment and irrespective of the type of treatment given. This rise may lead to microvascular and macrovascular complications.
Most people with type 2 diabetes will eventually need treatment with oral hypoglycaemic agents.
Metformin reduces glycated haemoglobin by 1−2% and reduces mortality compared with diet alone, without increasing weight, but it can cause hypoglycaemia compared with placebo.
Sulphonylureas reduce HbA1c by 1−2% compared with diet alone. Older sulphonylureas can cause weight gain and hypoglycaemia, but the risk of these adverse effects may be lower with newer-generation sulphonylureas.
Meglitinides (nateglinide, repaglinide) may reduce HbA1c by 0.4-0.9% compared with placebo, but may cause hypoglycaemia.
Combined oral drug treatment may reduce HbA1c levels more than monotherapy, but increases the risk of hypoglycaemia.
Insulin is no more effective than sulphonylureas in improving glucose control in people with newly diagnosed type 2 diabetes, and is associated with a higher rate of major hypoglycaemic episodes, and with weight gain.
Individual or group intensive educational programmes may reduce HbA1c compared with usual care, although studies have been of poor quality.
Insulin improves glycaemic control in people with inadequate control of HbA1c from oral drug treatment, but is associated with weight gain, and an increased risk of hypoglycaemia.
Adding metformin to insulin improves glucose control compared with insulin alone, but increases gastrointestinal adverse effects. However, the combination may cause less weight gain than insulin alone.
Monitoring of blood glucose levels has not been shown to improve glycaemic control in people not being treated with insulin.
Diet may be less effective than metformin or sulphonylureas in improving glucose control, although sulphonylureas were associated with higher rates of hypoglycaemia. However, there is consensus that weight reduction in people with type 2 diabetes can improve glycaemic control, as well as conferring other health benefits.