Comprehensive lifestyle interventions can reduce the incidence of type 2 diabetes(annals.org) in patients at increased risk for the disease, says a recent review and meta-analysis published in the Annals of Internal Medicine. The same types of interventions, however, do not appear to confer similar outcome benefits in those already diagnosed with type 2 diabetes.
Avoiding Disease Progression in At-risk Patients
According to data synthesized from nine randomized, controlled trials (RCTs) involving patients at risk for developing diabetes, interventions lasting six months or longer that included exercise, dietary changes and at least one other component, such as counseling or behavior modification, were effective in decreasing the incidence of progression to type 2 diabetes compared with usual care, a single-component intervention or assignment to a waiting list.
At-risk patients were defined as those who had one or more of the following risk factors:
- Comprehensive lifestyle interventions can reduce the incidence of type 2 diabetes patients at increased risk for the disease, a new meta-analysis finds.
- The same types of interventions do not confer similar benefits in patients already diagnosed with the disease.
- Longer-term studies may provide greater insight into which combination of interventions produces the most benefit.
- metabolic syndrome,
- insulin resistance,
- impaired fasting glucose,
- impaired glucose tolerance,
- syndrome X,
- dysmetabolic syndrome X and
- Reaven's syndrome.
Specifically, seven of the nine studies included in the analysis reported that comprehensive lifestyle interventions decreased diabetes risk from the end of the intervention to as long as 10 years afterward. Most of the studies also reported positive secondary outcomes, including beneficial changes in body composition, metabolic variables, physical activity levels and dietary intake.
Reducing Complications in Patients With Diagnosed Disease
However, "In patients who have already been diagnosed with type 2 diabetes, the evidence for benefit of comprehensive lifestyle interventions on patient-oriented outcomes is less clear," said the report's authors. That conclusion was based on an analysis of 11 RCTs involving patients with existing disease.
The patient-oriented outcomes of interest in this population were development of micro- and/or macrovascular complications, such as nephropathy, neuropathy, retinopathy, cardiovascular conditions and death. Secondary outcomes evaluated included surrogate markers for the development of these vascular complications, such as changes in body composition, metabolic variables (e.g., fasting blood glucose, hemoglobin A1c and lipid levels), blood pressure, physical activity, and dietary or nutrient intake.
Researchers found no evidence of benefit in all-cause mortality, and the evidence was insufficient to suggest benefit in cardiovascular and microvascular outcomes. Improvement was seen, however, for some secondary outcomes, but these gains generally did not persist beyond the intervention phase, and their clinical significance is unclear.
Study Limitations and Areas for Future Research
Study authors noted that only four of the nine studies involving patients at risk for type 2 diabetes and two of the 11 studies that focused on patients with existing disease reported on so-called patient-important outcomes. The remaining studies reported solely on secondary outcomes, which heightened the risk of bias. In addition, the strength of evidence was low or inadequate for most outcomes.
The lack of a commonly accepted definition of patients at risk for development of type 2 diabetes also is potentially problematic, the researchers noted. "This is a controversial area," they wrote, "with various definitions and diagnostic cut points having been proposed over the past few years."
Furthermore, said the authors, there was a great deal of heterogeneity among the lifestyle interventions used in the studies analyzed, particularly in the third component, rendering it difficult for the researchers to identify and comment on which interventions appeared to show benefit. Although all of the comprehensive lifestyle interventions studied for both groups included a diet and an exercise component and were supported by individual, group, and/or telephone counseling, the remaining interventions were wide-ranging and included smoking cessation, regular blood glucose and blood pressure monitoring, stress management, and others.
Finally, all of the studies included in the current review were RCTs, the authors acknowledged, whereas a review of cohort studies could permit a longitudinal assessment of different lifestyle interventions to determine the long-term sustainability and comparative effectiveness of the interventions employed.
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