Diabetic patients are at high risk for impaired renal function and its presence is associated with a high risk of cardiovascular disease and progression to end-stage renal disease (ESRD).1 Diabetes is the largest contributor to ESRD in the US, with glomerular filtration rate (GFR) impairment playing a key role in ESRD development.1,2 Urinary albumin levels provide a sensitive biomarker for GFR impairment and overall nephropathy. Albuminuria typically develops before GFR begins to decline and contributes to the risk of further GFR impairment.2,3
American Diabetes Association guidelines recommend intensive diabetes therapy for prevention of nephropathy and/or albuminuria.2,4 But is this an effective long-term solution? This question is addressed by a study published in 2011 by the DCCT/EDIC Research Group that examined the long-term effects of intensive diabetes therapy on GFR in Type 1 diabetes who were initially enrolled in the landmark Diabetes Control and Complications Trial (DCCT).
The DCCT randomized Type 1 diabetics early after diagnosis to an intensive therapy group that received either an insulin pump or three or more insulin injections daily with the aim of achieving near-normal glucose concentrations (HbA1c <6.05%) or a conventional therapy group that received no more than one or two insulin injections daily with a goal of mere prevention of the symptoms of hyperglycemia. After an average of 6.5 years, patients who received intensive therapy had fewer microvascular complications with intensive treatment than those who received conventional therapy.5 The Epidemiology of Diabetes Interventions and Complications (EDIC) trial was an extension of the DCCT and continued to follow patients for 8 years. EDIC researchers found that long-term renal effects persisted and cardiovascular complications were lower in patients treated with intensive therapy.6 To further examine the long-term effects of intensive therapy, DCCT/EDIC researchers followed the DCCT/EDIC patients for a median of 22 years after randomization in the DCCT with the primary objective to evaluate the development of impaired GFR (defined as an estimated GFR <60mL/min/1.73m2).7
Of the 1441 participants randomized in the DCCT, serum creatinine was evaluated in 1222 (84.8%) of the participants at the end of the 22-year follow-up. At this time, the participants’ mean age was 50 years, and mean duration of diabetes was 28 years; HbA1C was similar between the groups despite previous intensive or conventional therapy. More participants who had received conventional therapy in the DCCT had GFR impairment when compared to those who had intensive therapy (3.0/1000 person-years vs. 1.6/1000 person-years, respectively, p=0.006) resulting in a 50% decreased risk of GFR impairment.7 This corresponds to the need to treat 29 patients with intensive therapy for 6.5 years to prevent one person from developing impaired GFR after 20 years. Additionally, intensive therapy was associated with decreased risk of the composite outcome of impaired GFR or death by 37% (95% CI, 10-55, p=0.01).7 Over the course of these trials, the average decrease in estimated GFR per year was significantly greater with conventional therapy (1.56ml/min/m2, 95% CI 1.48-1.63) than with intensive therapy (1.27ml/min/1.73m2, 95% CI, 1.20-1.35, p<0.001). These benefits of intensive therapy were still significant when adjustments were made for between group differences in blood pressure, use of antihypertensive agents, or medications inhibiting the renin-angiotensin-aldosterone system. Consequently, it can be postulated that the benefits on GFR impairment and death are due in large part to intensive glycemic control early after diagnosis of Type 1 diabetes.
This trial showed that treating patients with Type 1 diabetes for an average of 6.5 years of intensive diabetes therapy reduced the long-term risk of an impaired GFR by 50%. A significant benefit in preventing ...