An individual’s ‘retinal age’ may be a clinically significant biomarker of aging, according to research published in the British Journal of Ophthalmology.
Describing the retinal age gap as the difference between a person’s biological (chronological) age and the biological age of their retina, the researchers suggested that this gap could be used as a screening tool.
Indeed, they pointed to growing evidence suggesting that the retina’s microvasculature could reliably predict the overall health of an individual’s unique circulatory system and brain.
The retina offers a unique, accessible ‘window’ to evaluate underlying pathological processes of systemic vascular and neurological diseases that are associated with increased risks of mortality
While the risk of illness and mortality rises with age, the risks vary significantly among people of the same age, meaning that biological age alone is not a reliable predictor of mortality. Tissue, cell, chemical, and imaging-based indicators can identify biological aging, however these are expensive and invasive, not to mention being associated with ethical and privacy concerns.
In search of an alternative approach, the researchers used deep learning to test whether it was possible to reliably predict a person’s retinal age from photographs of the fundus, and whether any gap between this and their actual age, might be linked to a higher risk of mortality.
To undertake this research, 80,169 fundus pictures from 46,969 adults aged 40 to 69 – participants in the UK Biobank – were reviewed.
A total of 19,200 fundus images from the right eyes of 11,052 participants who were in relatively good health at the initial Biobank health check were used to validate the accuracy of the deep learning model for retinal age prediction.
They found a substantial link between anticipated and actual retinal age, with an overall accuracy of 3.5 years.
The remaining 35,917 subjects had their retinal age gap measured after an average of 11 years of surveillance.
During this time, 1,871 participants (5%) died with 321 (17%) deaths caused by cardiovascular disease, 1018 (54.5%) by cancer, and 532 (28.5%) by other causes including dementia.
The proportions of ‘fast agers’; i.e. eyes with retinal age gaps of more than three, five, and 10 years were, respectively, 51%, 28%, and 4.5%.
Large retinal age gaps in years were linked to a 49% to 67% increased risk of mortality from causes other than cardiovascular disease or cancer.
Having accounted for factors such as high blood pressure, weight (BMI), lifestyle, and ethnicity which could influence mortality, the researchers observed that every one year increase in the retina age gap was associated with a 2% increase in the risk of death from any cause, and a 3% increase in the risk of death from a specific cause other than cardiovascular disease and cancer.
The same process applied to the left eyes produced similar results.
As an observational study the researchers acknowledged that they were unable to establish cause, however they concluded that, “Our novel findings have determined that the retinal age gap is an independent predictor of increased mortality risk, especially of non-[cardiovascular disease]/ non-cancer mortality. These findings suggest that retinal age may be a clinically significant biomarker of aging.
“The retina offers a unique, accessible ‘window’ to evaluate underlying pathological processes of systemic vascular and neurological diseases that are associated with increased risks of mortality.
“This hypothesis is supported by previous studies, which have suggested that retinal imaging contains information about cardiovascular risk factors, chronic kidney diseases, and systemic biomarkers.”
They explained that these findings, in conjunction with previous research, add weight to “the hypothesis that the retina plays an important role in the aging process and is sensitive to the cumulative damages of aging which increase the mortality risk”.