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Systemic inflammatory response index levels are associated with risk for age-related macular degeneration and may serve as a new biomarker for the condition.

Elevated systemic inflammatory response index (SIRI) levels are independently associated with an increased risk for age-related macular degeneration (AMD) among US residents, according to a study published in Frontiers in Nutrition.

A novel marker that quantifies inflammation using peripheral blood parameters, SIRI has been proposed as a predictor for cancer, cardiovascular disease, and other conditions. Given that chronic low-grade systemic inflammation also plays a key role in AMD pathogenesis, researchers investigated the association between SIRI and AMD.

The cross-sectional study used data from the National Health and Nutrition Examination Survey for participants aged 40 years and older. The analysis included 5,365 participants with data on SIRI and AMD status. The following formula was used to calculate SIRI: (Monocyte count × Neutrophil count)/Lymphocyte count.

Among participants, AMD affected 425 individuals, or 7.9% of the study sample.

“Participants with AMD were more likely to be older, Non-Hispanic White, of other marital status, and to have lower BMI, hypertension, and a history of former smoking compared to those without AMD (all p < 0.05),” the study team wrote.

SIRI As Potential Biomarker for AMD

The median SIRI was significantly higher among people with AMD (1.23) compared with those without AMD (1.04). In an analysis adjusted for a slate of cofounding factors, including age, sex, race, and marital status, a higher SIRI was independently linked with a higher likelihood of AMD (odds ratio [OR], 1.18).

Further analysis identified a dose-response relationship between SIRI and AMD risk, researchers found. By subgroup, higher SIRI scores significantly increased the risk for AMD in men, nonsmokers, and people with hypertension or obesity.

“These findings suggest that SIRI could be used as a biomarker for AMD risk assessment, which can greatly benefit patient care,” researchers wrote. “Since it is derived from peripheral blood, its measurement is straightforward, cost-effective, and non-invasive.”

The authors advised the need for prospective, longitudinal studies involving large cohorts to validate the findings and provide insight into the causal relationship between SIRI and AMD.

“This in-depth understanding will be instrumental in developing more targeted and effective prevention and treatment strategies for AMD, ultimately benefiting a large number of patients worldwide,” they wrote.