A groundbreaking study has revealed that metformin, an inexpensive and widely prescribed medication for type 2 diabetes, could help protect against the most common cause of blindness in older adults. The research, conducted by the University of Liverpool and published in the BMJ, indicates that this common drug may significantly slow the progression of age-related macular degeneration (AMD).
Significant Reduction in AMD Progression Found
The study examined 2,545 participants aged 55 and over who had attended routine diabetic eye disease screening in Liverpool over a five-year period. Researchers analysed retinal photographs taken in 2011 and again in 2016, which were carefully graded by eye specialists using established classification systems. The images were categorised as Early AMD, Intermediate AMD, or Late AMD, with the latter stage being most likely to cause serious vision impairment.
By cross-referencing GP records to identify which participants were prescribed metformin, the research team compared how frequently AMD developed or worsened between those taking the medication and those not taking it. The findings were striking: diabetic patients taking metformin were 37% less likely to develop intermediate AMD over the five-year study period compared to their counterparts not using the drug.
Understanding Age-Related Macular Degeneration
Age-related macular degeneration is the leading cause of sight loss in older people, affecting approximately 600,000 individuals in the United Kingdom. The condition typically first appears in people's 50s and causes the light-sensitive tissue at the back of the eye to deteriorate or become damaged by abnormal blood vessel growth. While AMD rarely causes complete blindness, it significantly impairs central vision, creating blurry and distorted sight, blind spots, and making activities like reading and facial recognition challenging.
The NHS estimates that at age 60, about one in every 2,000 people has AMD, but by age 90, this increases dramatically to affect one person in five. Although there is no single identified cause, age and lifestyle factors including smoking, obesity, alcohol consumption, and diets high in processed foods while low in nutrient-dense fruits and vegetables all increase the risk of developing the condition.
Current Treatment Landscape and Potential Breakthrough
Currently, there is no licensed treatment specifically for AMD, making this discovery particularly significant. Dr Nick Beare, the eye doctor who led the research, emphasised the importance of these findings: 'Most people who suffer from AMD have no treatment, so this is a great breakthrough in our search for new treatments. What we need to do now is test metformin as a treatment for AMD in a clinical trial. Metformin has the potential to save many people's sight.'
The researchers theorise that metformin might help protect the retina through its anti-ageing and anti-inflammatory properties. Metformin, which has been in clinical use for over six decades, works by reducing the amount of sugar the liver produces and improving the body's response to insulin, the hormone that regulates blood sugar levels.
Study Limitations and Future Research Directions
While the findings are promising, the study authors noted several important limitations. The research did not demonstrate that metformin reduces the chance of developing early AMD or slows progression from early to more advanced stages of the disease. Additionally, the metformin group in the study was slightly younger and healthier in some respects, and there was limited information about exact dosages and duration of medication use.
Furthermore, the study lacked data about participants' dietary habits or regular vitamin supplement use, and the results specifically apply to people with diabetes rather than the general population. These factors highlight the need for further investigation through controlled clinical trials to establish metformin's effectiveness as a treatment for AMD in broader patient groups.
Broader Implications and Economic Impact
The potential implications of this research are substantial, both medically and economically. Intermediate and advanced AMD affects 10-15% of people over 65, equating to 1.1 to 1.8 million individuals in the UK alone. The condition represents the most common cause of blindness in high-income countries, with the annual cost of AMD estimated at £11.1 billion in the United Kingdom.
Advanced AMD involves significant central vision loss and is classified into two types: dry and wet. Dry AMD involves the gradual degeneration of macular cells, leading to slowly enlarging blind spots, while wet AMD is characterised by rapid, aggressive vision loss caused by abnormal, leaky blood vessels developing under the retina.
Metformin's Versatile Medical Profile
This discovery adds to growing evidence of metformin's versatility beyond diabetes management. Recent studies have found that the medication may help prevent acute myeloid leukaemia, a particularly aggressive blood cancer that claims approximately four out of five patients. Scientists first identified the link between metformin and anti-cancer benefits in mouse experiments before confirming similar results in human studies.
At just 35p per pill for the NHS, metformin represents an exceptionally cost-effective medication. Its potential application in AMD treatment could offer an accessible therapeutic option for a condition that currently lacks licensed treatments. Research into new AMD treatments continues globally, with recent studies exploring innovative approaches including tiny chips implanted in the back of the eye to restore vision loss.
The University of Liverpool study marks an important step forward in understanding how existing medications might be repurposed to address significant public health challenges. As research progresses, metformin could potentially transform the management of age-related macular degeneration, offering new hope to hundreds of thousands of people affected by this vision-impairing condition.
