Overall, these new data suggest that age-related macular degeneration (AMD) is a clinical risk factor for increased risk of infection and mortality. These findings are consistent with those of previous studies suggesting that AMD confers a higher risk of serious complications from SARS-CoV-2 infection, including respiratory distress and death, estimated at 25%, a higher risk than that associated with type 2 diabetes (21%) and obesity (13%).
This increased risk may have a genetic basis
The Boston University researchers also hypothesized that AMD and COVID-19 share common genetic risk factors and designed the study to identify the variants involved.
The study conducted on a genome-wide scale, searched for variants jointly associated with AMD and each of the three COVID-19 outcomes (infection rate, severe illness and hospitalization) using large genetic datasets containing dozens of thousands of attendees. Once PDGFB was suspected, the researchers analyzed the causal relationships between PDGFB gene variants, blood platelet-derived growth factor (PDGF) concentration, AMD, and COVID-19 outcomes. The analysis suggests that:
- certain variants of the PDGFB gene are indeed involved in the development of these 2 conditions. The PDGFB gene encodes a platelet-derived growth factor (PDGF) that plays a role in the formation of new blood vessels and is involved in the abnormal blood vessel changes also characteristic of AMD.
- Severe COVID associated with AMD thus probably results
a genetic predisposition to a dysfunction involving proteins of the complement system,
- as well as a higher level of PDGFB in the blood serum;
- the decrease in PDGFB gene activity and serum PDGF concentration may therefore reduce the severity of COVID-19, especially in the elderly;
“Study Adds to Evidence of Increased Risk of COVID-19 Infection and Mortality in Patients with AMD,” confirms one of the main authors, Lindsay A. Farrer, chief of the department of biomedical genetics at Boston University.
This finding of shared genetic risk factors calls for broader study to better identify common risk factors that contribute to worsening clinical outcomes for both diseases.