What was the aim of this review?
The aim of this review was to find out whether fenofibrate prevents people with either type 1 (T1D) or type 2 (T2D) diabetes from developing diabetic retinopathy (DR), or if they already had DR, whether it slows its progression, when compared with placebo or observation.
- overall, fenofibrate likely made little to no difference in the progression of DR when compared with placebo (moderate-certainty evidence)
- for people with DR, their DR likely progressed slowly when they took fenofibrate (moderate-certainty evidence)
- although rare, side effects increased when people took fenofibrate (high-certainty evidence)
- more studies are needed; for example, studies that include people with type 1 diabetes, studies that take into account other treatments that people received, and importantly, studies that include outcomes that are important to people living with diabetes
What was studied in the review?
DR, a condition that occurs when the blood vessels in the back of your eye develop problems, is a major cause of sight loss worldwide and a burden to society. Preventing its occurrence, and if present, slowing or preventing its progression must be pursued to save sight. This review summarised the evidence about whether fenofibrate may be useful for this purpose (when compared to placebo or observation).
What are the main results of the review?
We found two studies. In total, they included 15,313 people with T2D, who were followed for four or five years. The studies were conducted in the US, Canada, Australia, Finland, and New Zealand. One was funded by the government, the other by industry.
For people with T2D, when those who may or may not have had DR were studied together, moderate-certainty evidence suggested that fenofibrate likely made little to no difference in the progression of DR when compared with placebo. However, when people with DR were studied on their own, the evidence suggested that their DR progressed slowly when they were taking fenofibrate. Serious adverse events were rare, but the risk of their occurrence increased for those who took fenofibrate (high-certainty evidence).
More studies are needed. For example, studies that include people with type 1 diabetes, and importantly, studies that include outcomes that are important to people living with diabetes, such as the number of people who experience a change in vision or sight loss, develop proliferative diabetic retinopathy (growth of new blood vessels), or require injections of anti-vascular endothelial growth factor therapies, or steroids. Health-related and vision-related quality of life measures, acceptability of the treatment to people using it, and costs of the treatment should be also included.
How up-to date is this review?
The review authors searched for studies published up to 1 February 2022.
Current, moderate-certainty evidence suggests that in a mixed group of people with and without overt retinopathy, who live with T2D, fenofibrate likely results in little to no difference in progression of diabetic retinopathy. However, in people with overt retinopathy who live with T2D, fenofibrate likely reduces the progression.
Serious adverse events were rare, but the risk of their occurrence was increased by the use of fenofibrate.
There is no evidence on the effect of fenofibrate in people with T1D. More studies, with larger sample sizes, and participants with T1D are needed. They should measure outcomes that are important to people with diabetes, e.g. change in vision, reduction in visual acuity of 10 ETDRS letters or more, developing proliferative diabetic retinopathy; and evaluating the requirement of other treatments, e.g. injections of anti-vascular endothelial growth factor therapies, steroids.
Diabetic retinopathy (DR) remains a major cause of sight loss worldwide, despite new therapies and improvements in the metabolic control of people living with diabetes. Therefore, DR creates a physical and psychological burden for people, and an economic burden for society. Preventing the development and progression of DR, or avoiding the occurrence of its sight-threatening complications is essential, and must be pursued to save sight. Fenofibrate may be a useful strategy to achieve this goal, by reversing diabetes’ effects and reducing inflammation in the retina, as well as improving dyslipidaemia and hypertriglyceridaemia.
To investigate the benefits and harms of fenofibrate for preventing the development and progression of diabetic retinopathy in people with type 1 (T1D) or type 2 diabetes (T2D), compared with placebo or observation.
We searched CENTRAL, MEDLINE, Embase, and three trials registers (February 2022).
We included randomised controlled trials (RCTs) that included people with T1D or T2D, when these compared fenofibrate with placebo or with observation, and assessed the effect of fenofibrate on the development or progression of DR (or both).
We used standard Cochrane methods for data extraction and analysis.
Our primary outcome was progression of DR, a composite outcome of 1) incidence of overt retinopathy for participants who did not have DR at baseline, or 2) advancing two or more steps on the Early Treatment Diabetic Retinopathy Study (ETDRS) severity scale for participants who had any DR at baseline (or both), based on the evaluation of stereoscopic or non-stereoscopic fundus photographs, during the follow-up period. Overt retinopathy was defined as the presence of any DR observed on stereoscopic or non-stereoscopic colour fundus photographs.
Secondary outcomes included the incidence of overt retinopathy, reduction in visual acuity of participants with a reduction in visual acuity of 10 ETDRS letters or more, proliferative diabetic retinopathy, and diabetic macular oedema; mean vision-related quality of life, and serious adverse events of fenofibrate.
We used GRADE to assess the certainty of evidence.
We included two studies and their eye sub-studies (15,313 participants) in people with T2D. The studies were conducted in the US, Canada, Australia, Finland, and New Zealand; follow-up period was four to five years. One was funded by the government, the other by industry.
Compared to placebo or observation, fenofibrate likely results in little to no difference in progression of DR (risk ratio (RR) 0.86; 95% confidence interval (CI) 0.60 to 1.25; 1 study, 1012 participants; moderate-certainty evidence) in a population with and without overt retinopathy at baseline. Those without overt retinopathy at baseline showed little or no progression (RR 1.00, 95% CI 0.68 to 1.47; 1 study, 804 participants); those with overt retinopathy at baseline found that their DR progressed slowly (RR 0.21, 95% CI 0.06 to 0.71; 1 study, 208 people; test for interaction P = 0.02).
Compared to placebo or observation, fenofibrate likely resulted in little to no difference in either the incidence of overt retinopathy (RR 0.91; 95% CI 0.76 to 1.09; 2 studies, 1631 participants; moderate-certainty evidence); or the incidence of diabetic macular oedema (RR 0.39; 95% CI 0.12 to 1.24; 1 study, 1012 participants; moderate-certainty evidence).
The use of fenofibrate increased severe adverse effects (RR 1.55; 95% CI 1.05 to 2.27; 2 studies, 15,313 participants; high-certainty evidence).
The studies did not report on incidence of a reduction in visual acuity of 10 ETDRS letters or more, incidence of proliferative diabetic retinopathy, or mean vision-related quality of life.