Serum 25(OH)D Shown to Have Differential Association with Early and Late Age-Related Macular Degeneration

by | Jun 1, 2023 | 2023, Eye Health, Vitamin D - General

Written by Taylor Woosley, Staff Writer. The rate of late age-related macular degeneration in the serum 25(OH)D sufficiency group was lower than that of the deficiency group (1.06% versus 1.62%), and this trend was more apparent among subjects over 60 years (2.06% versus 3.82%). 

eye healthAge-related macular degeneration (AMD) is the most common cause of irreversible vision loss in persons over age 65, with over 200 million people affected by AMD worldwide1. AMD is the consequence of a multifactorial interaction of metabolism, genetics and the environment, and these multiple factors foster a stage conducive for the chronic structural changes in the macular area2. Oxidative stress contributes to oxidized proteins, lipids, and DNA in aged tissues leading to increased pro-inflammatory responses3.

Vitamin D has diverse functions in maintaining human health, including regulating gene expression, immune system, cell proliferation and differentiation, and apoptosis4. Vitamin D can play a role in reducing chronic oxidative stress, inhibiting chronic inflammation, and therefore also reducing angiogenesis5. Accumulating observation evidence suggests that individuals with higher dietary intake or blood levels of vitamin D (25(OH)D) may have lower rates of AMD6.

Fu et al. conducted a study using data from the National Health and Nutrition Examination Survey III (NHANES III) 2005-2006 and 2007-2008 cycles to examine the relationship between serum 25-hydroxyvitamin D [25(OH)D] levels and the odds of different subtypes of AMD with a focus on exploring their non-linear relationship. NHANES is a population-based cross-sectional program using national data on the health and nutritional status of the US population. Each cycle contains information pertaining to demographic, socioeconomic, dietary, and health-related questions and subjects participate in an examination component comprising medical, dental, and physiological measurements and laboratory tests. Only participants with recorded serum 25(OH)D, AMD, and sufficient covariates (obesity, smoking status, and alcohol consumption) were included in the study. Serum 25(OH)D levels were divided into three categories: deficient (<30 nmol/L), insufficient (30-50 nmol/L), and sufficient (>50nmol/L).

The unpaired t-test for categorical variables and the Pearson x2 test for categorizing data were used to compare general characteristics of participants. To estimate odds ratios (ORs) of AMD according to serum 25(OH)D level, logistic regression models were established adjusting for demographic variables, lifestyle variables, age, and medical history variables. Restricted cubic spline (RCS) logistic regression analyses were utilized to investigate non-linear relations with three knots to model the association between AMD subtypes and serum 25(OH)D level.

A total of 5041 participants were included in the final analysis. 405 subjects (8.0%) had diagnosed AMD, including 354 with the early stage (7.0%) and 51 with the late stage (1.0%). The average concentration of serum 25(OH)D in the population was 60.1 ± 22.4 nmol/L. Mean serum 25(OH)D concentration was significantly higher in AMD individuals as compared to non-AMD ones (64.1 ± 22.3 nmol/L versus 59.8 ± 22.4 nmol/L; p < 0.001). Significant findings of the study are as follows:

  • The rate of early AMD increased with the increasing level of serum 25(OH)D. The rate of early AMD in the deficiency group was 4.20%, whereas that of the sufficiency group increased to 7.92%.
  • On the contrary, late AMD had an inverse relationship with the serum 25(OH)D level. The rate of late AMD in the sufficiency group was lower than that of the deficiency group (1.06% versus 1.62%), and this trend was more apparent among subjects over 60 years (2.06% versus 3.82%).
  • Results of multivariable logistic regression shows that participants in the sufficiency 25(OH)D group showed significantly higher odds of being diagnosed as having early AMD in crude models. However, the relationship disappeared after adjusting for demographic, lifestyle, and medical comorbidity variables (p > 0.05).
  • In the <60 years population, no significant association was detected between any or early AMD and serum 25(OH)D.

Results of the study show that serum 25(OH)D had differential association with early and late AMD. Serum 25(OH)D level was positively associated with increased risk of early AMD in a linear pattern, while it was negatively associated with late AMD, showing an L-shaped relationship. Study limitations include the inability to establish a casual relationship between 25(OH)D and AMD based on the cross-sectional design of the study and the lack of subgroup analysis for the relation between late AMD and serum 25(OH)D.

Source: Fu, Yihang, Xiaoyun Chen, Sheng Luo, Shuangyan Jiang, Yuxiang Mao, and Wei Xiao. “Serum 25-Hydroxyvitamin D Is Differentially Associated with Early and Late Age-Related Macular Degeneration in the United States Population.” Nutrients 15, no. 5 (2023): 1216.

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Posted June 1, 2023.

Taylor Woosley studied biology at Purdue University before becoming a 2016 graduate of Columbia College Chicago with a major in Writing. She currently resides in Glen Ellyn, IL.

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