Clinical trials play a vital role in developing treatments for diabetic macular edema (DME) and diabetic retinopathy (DR), two serious eye diseases linked to diabetes. With an estimated 22% of people with diabetes worldwide affected by DR, a chronic condition damaging blood vessels in the retina, the need for effective treatments is clear. Left untreated, DR can lead to DME, where weakened blood vessels in the retina leak fluid, causing swelling and potentially leading to vision loss.
“Diabetes is increasing in the U.S., and as a result, related complications like DME and DR are expected to rise,” said Dr. Benjamin Bert, an ophthalmologist at MemorialCare Orange Coast Medical Center in Fountain Valley, California. “Research and new treatments for these conditions are essential, and clinical trials are crucial for assessing their benefits and risks.”
However, a recent study suggests that not all patients have equal access to these trials. Geographic and racial disparities in trial participation may influence the outcomes of DME research.
Geographic Disparities in Clinical Trials
A study published in Eye journal examined the geographic distribution of clinical trials for DME and DR in the U.S. The research focused on phase 2 to phase 4 trials, involving more than 50 patients between 2000 and 2023.
“We found a significant geographic imbalance in the distribution of DME trials,” said Jainam Shah, a medical student at Albert Einstein College of Medicine and lead author of the study. “75% of DME trials took place in the South, with 25% in the West. There were no DME trials in the Midwest or Northeast.”
In contrast, DR trials were more evenly spread: 37% took place in the South, 37% in the Midwest, 14.8% in the West, and 11.1% in the Northeast.
Shah noted that this imbalance could reflect gaps in healthcare access, particularly in major cities with high diabetes rates like Chicago, New York, and Boston. These cities, despite their large, diverse populations, had no DME trials listed in the study. This highlights an underutilization of large academic hospitals, which serve racially and socioeconomically diverse communities.
Shah also cautioned that the study may underestimate the true extent of geographic exclusion, as it only considered single-center trials. Many multicenter trials report global data without specifying how many participants come from each site, making it harder to assess regional disparities accurately.
Racial Disparities in Clinical Trial Participation
The study also suggests that racial disparities may exist in DME and DR trial participation, although the lack of detailed demographic data limited the researchers’ ability to draw concrete conclusions. The ClinicalTrials.gov dataset does not consistently report race and ethnicity, making it difficult to assess racial representation in clinical trials.
“Urban areas in the Midwest and Northeast, which have large Black, Hispanic, and immigrant populations, were completely absent from DME trial participation,” Shah explained. “This raises concerns about lack of access for underrepresented minority groups.”
Social factors such as income, healthcare access, and insurance status, which are strongly linked to race, may further contribute to these disparities. Shah added that these factors could influence how trial sites are selected by sponsors.
A separate analysis of data from DRCR Retina Network trials, published in the American Journal of Ophthalmology, found that Asian and Hispanic participants had more severe DME at trial enrollment but were underrepresented in the studies. Similarly, a meta-analysis in JAMA Ophthalmology showed that while race did not influence visual outcomes for DME patients treated with ranibizumab, racial subgroups were still underrepresented in the trials.
Impact of Disparities on Trial Outcomes
While Shah’s study did not measure clinical outcomes directly, the findings point to significant concerns regarding the representativeness of DME trials. “The concentration of DME trials in public institutions, and their underrepresentation in academic centers, limits the diversity of trial participants,” Shah said.
Public institutions conducted 58.1% of DME trials, while private sponsors led 4.2 times more DR trials. Academic centers, which serve diverse populations, accounted for only 7% of DME trials and 15.7% of DR trials.
Shah argued that this concentration of trials in specific regions and institutions risks excluding diverse patient populations, which may have different disease presentations and treatment responses. He also noted that sponsors often prioritize sites with faster recruitment rates, contributing to the imbalance. This creates “trial deserts” in major cities and academic hubs, potentially limiting early access to new treatments.
Dr. Bert echoed these concerns, stressing the importance of including a broad range of participants in diabetic eye disease trials. “For studies to be truly representative, they must include people from diverse geographic areas, socioeconomic backgrounds, and races,” he said. “This requires more funding and the involvement of academic centers across the country.”
Conclusion
The study highlights significant geographic and racial disparities in the clinical trials for diabetic eye diseases like DME and DR. These inequities not only affect trial participation but may also impact the generalizability of trial outcomes, leaving underserved populations with limited access to emerging treatments. Efforts to address these disparities are crucial to ensure that future trials reflect the diverse experiences of all patients affected by these conditions.
Related Topics
