Relative fat mass and myopia in adolescents: a cross-sectional study using NHANES data

Adolescence is a peak period for myopia onset, which is closely related to environmental and lifestyle factors. Relative fat mass (RFM), a novel indicator of body fat, provides a more precise measure of adiposity. However, its relationship with myopia in adolescents remains poorly understood. To probe the connection between RFM and myopia in adolescents, this study included 8746 adolescents aged 12-19 years, utilizing data from the National Health and Nutrition Examination Survey (1999-2008). Myopia was defined as a spherical equivalent (SE) ≤ -1.0 D. The relationship between RFM and adolescent myopia was assessed using a weighted logistic regression model. Restricted cubic spline analysis was employed to examine the nonlinear relationship between RFM and the odds of myopia. Subgroup analysis and interaction tests were also conducted. Sensitivity analyses were performed using broader myopia diagnostic criteria (SE ≤ -0.75 D and SE ≤ -0.50 D). After adjusting for all confounding factors, the odds of myopia in the third and highest quartiles of RFM were 33% higher (odds ratio (OR) = 1.33, 95% CI: 1.07-1.64) and 35% higher (OR = 1.35, 95% CI: 1.01-1.80), respectively, compared to the lowest quartile. Each one-standard-deviation (9.06) increase in RFM was associated with a 12% higher odds of myopia in adolescents (OR = 1.12, 95% CI: 1.01-1.25). This association was more pronounced in males (OR = 1.25, 95% CI: 1.09-1.43). A significant positive association was also observed in the low-income population (OR = 1.27, 95% CI: 1.08-1.49). Sensitivity analysis showed that when using SE ≤ -0.75 D and SE ≤ -0.50 D as the diagnostic criteria for myopia, RFM remained significantly positively associated with the odds of adolescent myopia, indicating the robustness of the results. Increased RFM was significantly associated with higher odds of myopia in adolescents, with a stronger association observed among males, suggesting that body fat control and RFM reduction may represent a promising direction for comprehensive myopia prevention and management in adolescents. Targeted interventions integrating weight management, healthy diet, regular physical activity, and accessible eye health services could be developed, particularly for male and low-income adolescents. However, longitudinal studies are needed for further validation.