medwireNews: People with impaired glucose tolerance who received metformin or intensive lifestyle intervention during the DPP trial show no sign of a significantly reduced cardiovascular disease (CVD) risk 21 years later, reveal the latest DPPOS results.
This was despite earlier findings that people given either intervention had a significantly reduced risk for progression to type 2 diabetes compared with those who took placebo.
For this latest analysis, the researchers followed up the participants for a median of 21 years, including the 3 years of DPP, for first nonfatal myocardial infarction or stroke, or cardiovascular death; this occurred in 310 of the 3234 people.
The event rates per 1000 person–years were 5.51, 6.10, and 5.28 for people originally in the metformin, intensive lifestyle, and placebo groups, respectively, with no significant differences between them.
This was also the case across prespecified subgroups defined by age, sex, race or ethnicity, or progression to type 2 diabetes.
Addressing the lack of effect, Ronald Goldberg (University of Miami Miller School of Medicine, Florida, USA) and study co-authors say that the overall CVD rate during follow-up was low, as was the average glycated hemoglobin level, at just 6.0–6.1% (42–43 mmol/mol), despite all trial participants having impaired glucose regulation at baseline.
In addition, systolic blood pressure averaged 121–122 mmHg and low-density lipoprotein cholesterol averaged 2.81–2.85 mmol/L.
“This was therefore a relatively low-risk cohort from the standpoint of the prevention of CVD,” write the researchers in Circulation. “It is thus possible that the accelerating effect of the duration of clinically diagnosed diabetes on cardiovascular risk has still not had enough time to manifest.”
They also point out the “extensive out-of-study use of lipid-lowering and antihypertensive medications, provision of a less intensive lifestyle intervention to all DPPOS participants, and increased out-of-study metformin use over time, which may both have limited the apparent effects of the interventions and have been valuable preventive strategies.”
The team therefore concludes: “Metformin and lifestyle intervention reduce the risk of type 2 diabetes, but may not provide additional protection against cardiovascular disease when glycemia, lipids, and blood pressure are well controlled.”
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