The New England Journal of Medicine JANUARY 08, 2009

Glucose Control and Vascular Complications in Veterans with Type 2 Diabetes

William Duckworth, Carlos Abraira, Thomas Moritz, et al. (VADT Investigators)

Bottom Line

In patients with long-standing, poorly controlled type 2 diabetes and high cardiovascular risk, intensive glucose-lowering therapy did not significantly reduce the rate of major cardiovascular events compared to standard therapy.

Key Findings

1. The primary outcome (composite of myocardial infarction, stroke, cardiovascular death, congestive heart failure, surgery for vascular disease, or amputation for ischemic gangrene) occurred in 29.5% of the intensive-therapy group versus 33.5% in the standard-therapy group (Hazard Ratio 0.88; 95% CI 0.74-1.05; P = 0.14).

2. There was no significant difference in all-cause mortality between the intensive (11.4%) and standard (10.6%) groups (P = 0.62).

3. Hypoglycemia was significantly more frequent in the intensive-therapy group, with an incidence of 1,566 events per 100 patient-years, compared to 432 events per 100 patient-years in the standard-therapy group (P < 0.0001).

4. Long-term follow-up (up to 15 years) showed no evidence of a 'legacy effect' or lasting cardiovascular benefit from the initial 5.6 years of intensive glucose lowering.

Study Design

Design

RCT

Open-Label

Sample

1,791

Patients

Duration

5.6 yr

Median

Setting

Multicenter, US

Population Veterans with long-standing, poorly controlled type 2 diabetes (HbA1c >7.5%) despite maximal oral or insulin therapy and high cardiovascular risk.

Intervention Intensive glucose-lowering therapy targeting an HbA1c <6.0%.

Comparator Standard glucose-lowering therapy targeting an HbA1c 1.5% higher than the intensive arm.

Outcome Composite of myocardial infarction, stroke, cardiovascular death, new or worsening congestive heart failure, surgery for vascular disease, inoperable coronary artery disease, and amputation for ischemic gangrene.

Study Limitations

• The study population was predominantly male (veterans), which limits the generalizability of findings to female patients.

• The trial was open-label, which could introduce bias in the management of non-glycemic risk factors or self-reporting of outcomes.

• The high incidence of hypoglycemia in the intensive treatment arm highlights the challenges and risks associated with aggressive glycemic targets in this high-risk population.

• The study may have been underpowered to detect smaller but clinically relevant differences in specific macrovascular outcomes.

Clinical Significance

The trial challenged the prevailing belief that aggressive glycemic control in advanced type 2 diabetes universally yields macrovascular protection, shifting clinical focus toward personalized glycemic goals and emphasizing the importance of managing other cardiovascular risk factors, such as blood pressure and lipids, over sole reliance on tight glycemic control.

Historical Context

Published alongside ACCORD and ADVANCE trials, VADT was part of a landmark trio of studies that significantly reshaped diabetes management guidelines in the late 2000s, tempering enthusiasm for 'lower is better' glycemic targets in high-risk patients with long-standing disease due to the observed risks of hypoglycemia and lack of clear macrovascular benefit.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

Why does intensive glucose control often yield significant improvements in microvascular outcomes (like retinopathy) but fail to demonstrate a similar immediate reduction in macrovascular events (like myocardial infarction) in trials such as VADT?

Key Response

Microvascular complications are more directly and linearly related to glycemia through pathways like the polyol and hexosamine pathways. Macrovascular disease (atherosclerosis) is multifactorial, involving long-term processes like advanced glycation end-product (AGE) accumulation in vessel walls that may become irreversible (metabolic memory) before intensive therapy is initiated in long-standing diabetes.

Resident

In an elderly veteran with a 15-year history of Type 2 Diabetes, an HbA1c of 9.2%, and a previous history of stroke, how does the VADT study influence your selection of a target HbA1c?

Key Response

The VADT trial demonstrated that in patients with long-standing T2DM and high CV risk, intensive control (A1c target <7%) did not reduce MACE and increased the risk of severe hypoglycemia. For this patient, a more relaxed target (e.g., 7.5%–8.0%) is appropriate to balance the lack of proven CV benefit against the high risk of treatment-related harm.

Fellow

Contrast the VADT results with the 10-year follow-up of the UKPDS. How do these studies collectively define the 'window of opportunity' for intensive glycemic control?

Key Response

UKPDS showed a 'legacy effect' where early intensive control in newly diagnosed patients led to long-term CV benefits. VADT, ACCORD, and ADVANCE included patients with an average duration of >10 years of diabetes. This suggest that intensive control must be implemented early in the disease course (the window of opportunity) before established macrovascular damage occurs to realize a CV survival benefit.

Attending

VADT used a 'treat-to-target' approach primarily using older agents like insulin and sulfonylureas. How does the emergence of SGLT2 inhibitors and GLP-1 receptor agonists change the interpretation of VADT's null findings for cardiovascular risk reduction?

Key Response

VADT proved that lowering glucose *per se* with older agents does not significantly reduce CV events in high-risk patients. However, newer agents provide CV protection through mechanisms independent of HbA1c lowering (e.g., osmotic diuresis, anti-inflammatory effects). The modern approach has shifted from 'glucose-centric' to 'organ-protective,' where the choice of agent is now more critical than the absolute HbA1c level achieved.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

The VADT study used a composite primary endpoint including revascularization and heart failure alongside MI and stroke. How might this broader definition of 'major cardiovascular events' have impacted the study's power and its ability to detect a benefit specifically for atherosclerotic outcomes?

Key Response

Including heterogeneous outcomes like heart failure or revascularization increases the total event count, theoretically increasing power. However, if the intervention has divergent effects (e.g., intensive insulin causing weight gain/fluid retention which offsets benefits in stroke reduction), the composite hazard ratio is diluted toward the null, potentially masking a benefit in purely atherosclerotic endpoints (MACE-3).

Journal Editor

The VADT cohort was 97% male and consisted entirely of veterans. What are the primary threats to the external validity of these findings, and how should an editorial handle the generalizability of these results to female populations or different healthcare delivery systems?

Key Response

The extreme gender imbalance and the unique comorbidities (PTSD, high smoking rates) of the veteran population limit generalizability. An editor would require the authors to explicitly state these limitations and would likely seek a commentary to contextualize whether the physiological response to intensive insulin therapy in older men is truly representative of the broader T2DM population.

Guideline Committee

How do the VADT results support the ADA/EASD's recommendation for 'individualizing' glycemic targets, and what specific patient characteristics from this trial justify a Grade A recommendation for a less-stringent HbA1c target (>7.0%)?

Key Response

VADT provides high-level evidence that intensive control is not one-size-fits-all. Current ADA Standards (Section 6) utilize VADT to justify targets of <8.0% for patients with long duration of diabetes, limited life expectancy, or advanced microvascular/macrovascular complications, as the risk-benefit ratio in these subgroups favors avoiding hypoglycemia over achieving near-normoglycemia.

Clinical Landscape

Noteworthy Related Trials

1998

UKPDS 33

n = 3,867 · Lancet

Tested

Intensive glucose control with sulfonylurea or insulin

Population

Patients with newly diagnosed T2DM

Comparator

Conventional glucose control with diet

Endpoint

Any diabetes-related endpoint

Key result: Intensive blood-glucose control by either sulfonylureas or insulin substantially decreased the risk of microvascular complications.

2008

ACCORD Trial

n = 10,251 · NEJM

Tested

Intensive glucose control (HbA1c <6.0%)

Population

T2DM patients at high risk for cardiovascular disease

Comparator

Standard glucose control (HbA1c 7.0-7.9%)

Endpoint

Composite of nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascular causes

Key result: Intensive glucose lowering increased mortality compared to standard therapy and did not significantly reduce major cardiovascular events.

2008

ADVANCE Trial

n = 11,140 · NEJM

Tested

Intensive glucose control (target HbA1c 6.5%)

Population

Patients with T2DM at high risk for vascular events

Comparator

Standard glucose control

Endpoint

Composite of major macrovascular and microvascular events

Key result: Intensive glucose control reduced the incidence of major microvascular events, primarily nephropathy, but had no significant effect on major macrovascular events.

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