Statins for delaying the onset and progression of age-related macular degeneration

Review question
What are the effects of statins on delaying the onset and progression of age-related macular degeneration (AMD)?

Background
AMD is a progressive disease of the macula (area in the back of the eye affecting central vision). AMD is the leading cause of blindness in people over 65 years in industrialized countries. Studies have shown that some of the factors that may lead to heart disease and strokes are the same as those that may lead to AMD. Statins are a type of drug that aims to lower blood cholesterol levels. As statins are very effective in preventing strokes, it is possible that they are also protective for AMD.

Study characteristics
We included two trials (144 total participants) in this review. Participants included men and women, most of whom were older than 50 years, who had good visual acuity. Participants were either susceptible to or had been diagnosed with an early stage of AMD. Both trials compared simvastatin with placebo. The larger trial, with 114 participants and conducted in Australia, used a higher dose of 40 mg per day and had a treatment period of three years. The smaller trial, with 30 participants and conducted in Italy, used a lower dose of 20 mg per day and had a treatment period of three months. The evidence provided in this review was up-to-date as of March 2016.

Key results
Neither trial provided sufficient evidence to determine whether statins are effective in delaying the onset or progression of AMD. Information was lacking for outcomes related to vision, quality of life, and adverse events.

Quality of the evidence
The overall quality of the evidence was low. In the smaller trial, the number of participants enrolled and the short treatment period may not have been sufficient for detecting the effect of statins on AMD, which develops over time. In the larger trial, 30% of participants did not attend the three-year follow-up visit, and the amount of missing data hindered our ability to draw any reliable conclusions for this trial.

Authors' conclusions: 

Evidence from currently available RCTs is insufficient to conclude that statins have a role in preventing or delaying the onset or progression of AMD.

Read the full abstract...
Background: 

Age-related macular degeneration (AMD) is a progressive, late-onset disorder of the macula affecting central vision. It is the leading cause of blindness in people over 65 years in industrialized countries. Recent epidemiologic, genetic, and pathological evidence has shown that AMD shares a number of risk factors with atherosclerosis, leading to the hypothesis that statins may exert protective effects in AMD.

Objectives: 

The objective of this review was to examine the effectiveness of statins compared with other treatments, no treatment, or placebo in delaying the onset and progression of AMD.

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2016, Issue 3), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to March 2016), EMBASE (January 1980 to March 2016), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to March 2016), PubMed (January 1946 to March 2016), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) (last searched 5 June 2014), ClinicalTrials.gov (www.clinicaltrials.gov), and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 31 March 2016.

Selection criteria: 

We included randomized controlled trials (RCTs) and quasi-randomized trials that compared statins with other treatments, no treatment, or placebo in people who were diagnosed as having the early stages of AMD.

Data collection and analysis: 

We used standard methodological procedures expected by Cochrane. Two review authors independently evaluated the search results against the selection criteria, abstracted data, and assessed risk of bias. We did not perform meta-analysis due to heterogeneity in the interventions and outcomes between the included studies.

Main results: 

Two RCTs with a total of 144 participants met the selection criteria. Both trials compared simvastatin versus placebo in older people (older than 50 or 60 years) with high risk of developing AMD (drusen present on examination). Overall, we judged the quality of the evidence to be low, as we downgraded all outcomes due to limitations in the designs of the trials and insufficient outcome reporting. The larger trial, with 114 participants, was conducted in Australia and used a higher dose (40 mg daily) of simvastatin for three years. Participants and study personnel in this trial were adequately masked, however data were missing for 30% of participants at three years' follow-up. The smaller trial, with 30 participants, was conducted in Italy and used a lower dose (20 mg) of simvastatin for three months. This trial reported insufficient details to assess the risk of bias.

Neither trial reported data for change in visual acuity. Low-quality evidence from the smaller trial, with 30 participants, did not show a statistically significant difference between the simvastatin and placebo groups in visual acuity values at three months of treatment (decimal visual acuity 0.21 ± 0.56 in simvastatin group and 0.19 ± 0.40 in placebo group) or 45 days after the completion of treatment (decimal visual acuity 0.20 ± 0.50 in simvastatin group and 0.19 ± 0.48 in placebo group). The lack of a difference in visual acuity was not explained by lens or retina status, which remained unchanged during and after the treatment period for both groups.

Preliminary analyses of 42 participants who had completed 12 months' follow-up in the larger trial did not show a statistically significant difference between simvastatin and the placebo groups for visual acuity, drusen score, or visual function (effect estimates and confidence intervals were not available). Complete data for these outcomes at three years' follow-up were not reported. At three years, low-quality evidence showed an effect of simvastatin in slowing progression of AMD compared with placebo to be uncertain (odds ratio 0.51, 95% confidence interval 0.23 to 1.09).

One trial did not report adverse outcomes. The second trial reported no difference between groups in terms of adverse events such as death, muscle aches, and acute hepatitis.

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