Review: Intensive blood pressure control reduces retinopathy in diabetes Clinical impact ratings:
Do DV, Wang X, Vedula SS, et al. Blood pressure control for diabetic retinopathy. Cochrane Database Syst Rev. 2015;1:CD006127.
Question In patients with diabetes, what is the effect of interventions to control or reduce blood pressure (BP) on diabetic retinopathy?
Sources of funding: National Institutes of Health, USA; Research to Prevent Blindness; Wilmer Eye Institute; National Institute for Health Research, UK.
For correspondence: Dr. D. Do, University of Nebraska Medical Center, Omaha, NE, USA. E-mail [email protected]
Included studies compared intensive with less-intensive BP control, BP control with usual care or no intervention, or antihypertensive drugs with placebo in patients with type 1 or type 2 diabetes mellitus, with or without hypertension. Outcomes included diabetic retinopathy, progression of diabetic retinopathy, preservation of visual acuity, mortality, and hypotension.
Commentary The rigorous Cochrane review by Do and colleagues addresses the complex role of BP control on diabetic retinopathy. Blood glucose control reduces risk for diabetic retinopathy and slows progression in patients with the condition (1). The review indicates that the evidence for intensive BP control on incidence and progression of retinopathy is weak due to variability in study designs, populations, interventions, and outcomes. Intensive BP control reduces incidence of diabetic retinopathy in the initial 4 to 5 years of treatment, but there is no clear evidence on beneﬁcial effects on the progression of diabetic retinopathy.
Review methods MEDLINE, EMBASE/Excerpta Medica, Cochrane CENTRAL, LILACS, metaRegister of Controlled Trials, ClinicalTrials.gov, and World Health Organization International Clinical Trials Registry Platform (all to April 2014), and reference lists were searched for randomized controlled trials. 15 RCTs (n = 13 669) met selection criteria. 5 RCTs included patients with type 1 diabetes (n = 4036, mean age 30 y), and 10 RCTs included patients with type 2 diabetes (n = 8251, mean age range 51 to 66 y). 11 RCTs had adequate randomization, 10 had adequate allocation concealment, 12 had blinded outcome assessors, and 8 had adequate follow-up. 10 RCTs compared ≥ 1 antihypertensive agent with placebo, 3 RCTs compared intensive BP control with less-intensive BP control, and 2 RCTs compared BP control with usual care. Pharmaceutical companies sponsored 6 RCTs and partially supported 7 RCTs. Interventions were grouped for comparison of intensive BP control with less-intensive or no BP control.
The review included studies with heterogeneous groups of patients and provided subgroup results by type of diabetes and hypertension but not by such factors as duration of diabetes or BP targets. Also, the possibility of bias exists due to pharmaceutical company sponsorship of 6 RCTs and the unclear involvement of such sponsors in 7 additional RCTs. Diabetic retinopathy is complex, and further study is needed to increase our understanding of the condition, including which subgroups of patients with diabetes may beneﬁt from current speciﬁc antihypertensive medications and BP targets. Despite the lack of conclusive evidence of a protective effect on retinopathy, early treatment of hypertension is important in patients with diabetes, both to prevent cardiovascular disease and to minimize progression of renal disease (2).
Main results The main results are in the Table. Results did not differ by type 1 or type 2 diabetes.
Steven A. Smith, MD Shrikant Tamhane, MD Mayo Clinic Rochester, Minnesota, USA
Conclusion In patients with type 1 or type 2 diabetes mellitus, intensive control of blood pressure reduces incidence of retinopathy, increases hypotension, and does not affect progression of established retinopathy compared with less-intensive or no control of blood pressure.
References 1. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. The Diabetes Control and Complications Trial Research Group. N Engl J Med. 1993;329:977-86. 2. Gaede PH, Jepsen PV, Parving HH, Pedersen OB. [Intensiﬁed multifactorial intervention in patients with type 2 diabetes mellitus and microalbuminuria: the Steno-2 study]. Ugeskr Laeger. 1999;161:4277-85.
Intensive vs less-intensive or no blood pressure control in patients with diabetes* Outcomes
Number of trials (n)
Weighted event rates Intensive
At 4 to 5 y
RRR (95% CI)
NNT (CI) 18 (13 to 44)
20% (8 to 29)
Progression of retinopathy‡
12% (⫺5 to 27)
Retinopathy or progression
22% (3 to 37)
17 (11 to 124)
14% (⫺14 to 36)
Decreased visual acuity§
6% (⫺15 to 33)
108% (68 to 157)
15 (10 to 23)
*NS = not signiﬁcant; other abbreviations deﬁned in Glossary. Weighted event rates, RRR, RRI, NNT, NNH, and CI calculated from control event rates and risk ratios in article using a random-effects model. †Mild nonproliferative or more severe diabetic retinopathy based on stereoscopic color fundus photographs. ‡≥ 2-step progression from baseline on the Early Treatment Diabetic Retinopathy Study ﬁnal scale. §By ≥ 3 lines in both eyes on a logMAR chart.
16 Jun 2015
Annals of Internal Medicine
ACP Journal Club
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