Risks of progression of retinopathy and vision loss related to tight blood pressure control in type 2 diabetes mellitus: UKPDS 69

Matthews, David R., Stratton, Irene M., Aldington, Stephen J., Holman, Rury R. and Kohner, Eva M. (2004) Risks of progression of retinopathy and vision loss related to tight blood pressure control in type 2 diabetes mellitus: UKPDS 69. Archives of Ophthalmology, 122 (11), 1631-1640. (doi:10.1001/archopht.122.11.1631).

Abstract

Objective: to determine the relationship between tight blood pressure (BP) control and the different aspects of diabetic retinopathy in patients with type 2 diabetes mellitus (DM). 

Setting: nineteen hospital-based clinics in England, Scotland, and Northern Ireland. 

Design: outcome of retinopathy status assessed by 4-field retinal photography related to allocation within a randomized controlled trial comparing a tight BP control policy aiming for a BP less than 150/85 mm Hg with a less tight BP control policy aiming for a BP less than 180/105 mm Hg. 

Subjects: one thousand one hundred forty-eight hypertensive patients with type 2 DM were studied. These patients had type 2 DM for a mean duration of 2.6 years at the inception of the Hypertension in Diabetes Study, had a mean age of 56 years; and had a mean BP of 160/94 mm Hg. Seven hundred fifty-eight patients were allocated to a tight BP control policy with angiotensin-converting enzyme inhibitor or β-blockers as the main therapy; 390 were allocated to a less tight BP control policy. 

Main outcome measures: deterioration of retinopathy (≥2-step change on a modified Early Treatment Diabetic Retinopathy Study [ETDRS] final scale), together with end points (photocoagulation, vitreous hemorrhage, and cataract extraction) and analysis of specific lesions (microaneurysms, hard exudates, and cotton-wool spots). Visual acuity was assessed at 3-year intervals using ETDRS logarithm of the minimum angle of resolution charts. Blindness was monitored as an end point with the criterion of Snellen chart assessment at 6/60 or worse.

Results: by 4.5 years after randomization, there was a highly significant difference in microaneurysm count with 23.3% in the tight BP control group and 33.5% in the less tight BP control group having 5 or more microaneurysms (relative risk [RR], 0.70; P=.003). The effect continued to 7.5 years (RR, 0.66; P<.001). Hard exudates increased from a prevalence of 11.2% to 18.3% at 7.5 years after randomization with fewer lesions found in the tight BP control group (RR, 0.53; P<.001). Cotton-wool spots increased in both groups but less so in the tight BP control group which had fewer cotton-wool spots at 7.5 years (RR, 0.53; P<.001). A 2-step or more deterioration on the ETDRS scale was significantly different at 4.5 years with fewer people in the tight BP control group progressing 2 steps or more (RR, 0.75; P=.02). Patients allocated to tight BP control were less likely to undergo photocoagulation (RR, 0.65; P=.03). This difference was driven by a difference in photocoagulation due to maculopathy (RR, 0.58; P=.02). The cumulative incidence of the end point of blindness (Snellen visual acuity, S6/60) in 1 eye was 18/758 for the tight BP control group compared with 12/390 for less tight BP control group. These equate to absolute risks of 3.1 to 4.1 per 1000 patient-years, respectively (P=.046; RR, 0.76; 99% confidence interval, 0.29-1.99). There was no detectable difference in outcome between the 2 randomized therapies of angiotensin-converting enzyme inhibition and β-blockade. 

Conclusions: high BP is detrimental to each aspect of diabetic retinopathy; a tight BP control policy reduces the risk of clinical complications from diabetic eye disease.

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Contributors

Author: Irene M. Stratton

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