15-year outcomes
At the final 15-year follow up, with the HbA1c levels similar in the groups, nearly all benefits seen at 10 years were lost. Event rates for the CVD primary composite outcome were 51.8 and 47.3 per 1,000 patient-years in the intensive care and standard care groups, respectively (HR, 0.91; P = .23), and event rates for the renal composite outcome were 88 and 85 per 1,000 patient-years (HR, 0.90; P = .55).
Similarly, no differences were seen at 15 years in the secondary VADT-F outcomes of any major diabetes outcome, (HR, 0.90; P = .16), cardiovascular death (HR, 0.94; P = .61), or death from any cause (HR 1.02; P = .81), and no differences were seen in the individual components of the composite outcomes, the investigators said.
The same was true for other outcomes, including hospitalizations and health-related quality of life, Dr. Reaven said.
Ocular events studied in the VADT-F included cataract extraction, laster photocoagulation, vitrectomy, and intravitreal injections, with the latter three constituting a retinal event composite for which there was a difference of “very borderline significance (HR, 0.84; P = .053),” said Dr. Emanuele of Hines (Ill.) VA Hospital and Loyola University of Chicago.
There was no difference between groups for cataract extraction. (HR, 1.16; P = .30) or in participants’ self reported vision at 15 years, he added.
Additional analyses showed that there were no treatment interactions for results based on baseline differences in diabetes duration, prior CV events, or risk scores.
In essence, there was no evidence of a legacy effect, Dr. Reaven said, noting that the findings are “relatively consistent” with those from other recent glucose-lowering trials, including ACCORDION and ADVANCE-ON, which also showed no legacy benefits of intensive glucose lowering.
Dr. Emanuele also concluded that no prolonged legacy effect was apparent for renal and other microvascular outcomes.
Dr. Hertzel Gerstein
The lack of a legacy effect at 15 years, however, shouldn’t discount the benefits seen at the 10-year follow-up because there are other ways to look at “legacy,” Hertzel C. Gerstein, MD, said during an independent “clinical perspective” commentary on the VADT and VADT-F findings.
“Another way to define ‘legacy’ is what happens after the active clinical trial ends, and if you think of it that way, there is a legacy,” said Dr. Gerstein, a professor and Population Health Institute chair in diabetes research at McMaster University and Hamilton Health Sciences, Ontario, Canada.
That is, the intensive glycemic control led to significant improvements at 10-year follow-up. While he acknowledged “that’s just semantics,” he stressed that a number of important lessons have been learned from the VADT and VADT-F – not the least of which relate to mediation analyses that showed the benefit seen at 10 years can be explained, at least statistically, by the differences in HbA1c levels achieved during those intervening 10 years of follow-up.
For example, the 10-year cardiovascular outcome hazard ratios changed from 0.83 with a P value of .04 to 0.86 with a P value of .12 (after controlling for time-varying HbA1c levels) and to 0.94 with a P value of .53 (after controlling for time-varying cumulative mean HbA1c), he said, noting that similar findings have been reported from prior trials.