In a Chinese population, higher salt intake was linked to sooner AMD development. Photo: Milada Vigerova on Unsplash.
Many studies have verified that a healthy lifestyle may decrease the risk of age-related macular degeneration (AMD). However, most were conducted in western countries; big data studies are still lacking in China. Researchers believe that determining the epidemiologic features of AMD in China and the influence of dietary patterns on this disease may provide reference information for health policy and health care in China and other countries. A recent study published in BMC Ophthalmology noted that there was a high frequency of early AMD detected through health examination in patients over 60 years old. Notably, high salt intake increased the risk of early AMD (odds ratio: 1.61), whereas intake of meat decreased the risk (odds ratio: 0.90).
The researchers used the National Unified Physical Examination Questionnaire to collect dietary data from 43,672 participants older than 50 in Hunan, China. The diagnosis of AMD was based on the results of color fundus photography, spectral-domain OCT and multispectral imaging.
In these participants, 2.5% had early AMD. The frequencies were 2.6% in men and 2.3% in women and 1.0%, 3.6% and 9.1% in the 50 to 59, 60 to 69 and ≥70 age groups, respectively. The study found that 2.8% had AMD overall, including 2.5% early AMD and 0.34% late AMD cases. The frequency of early AMD increased gradually with age in both men and women. Multivariate logistic regression analysis demonstrated that BMI, salt intake and smoking increased the risk of early AMD in these patients, while meat consumption and alcohol drinking decreased the risk of early AMD. The data demonstrated that the average salt intake was 8.39g/day in participants without AMD and 9.26g/day in those with early AMD. Stratified analysis showed that high salt intake may have a greater impact on patients without hypertension.
The data indicated that the salt intake of the elderly population in Hunan was much higher than the recommended level, severely affecting the health of the eyes and the body of citizens. The high salt intake of these participants was related to their eating habits. The researchers explained that the most common source of salt (about 70%) was from processed food. Salt intake increased rapidly with increased consumption of processed food.
However, the dietary pattern adopted by the elderly subjects in the study is high-fat and meat-dominant with limited carbohydrates, which is similar to the characteristics of a ketogenic diet. The researchers proposed that this observation needs to be validated in a prospective cohort study. They concluded in their paper, “Modulating the dietary pattern and reducing the salt intake as an AMD prevention strategy warrant further study.”
Lin Y, Peng T, Li Y, Liu Y. The frequency of early age-related macular degeneration and its relationship with dietary pattern in Hunan, China: a cross-sectional study. BMC Ophthalmol. July 27, 2022. [Epub ahead of print].