Analysis of bibliometric and cross-cycle NHANES data: The effects of physical activity and vitamin D on pubertal onset in children aged 6–14 and the differences before and after the pandemic

This study integrates bibliometric analysis with pre- and post-pandemic data from National Health and Nutrition Examination Survey cycles to examine the interrelationships between physical activity (PA), 25-hydroxyvitamin D (25(OH)D) levels, and pubertal status in children aged 6 to 14 years, as well as the dynamic changes in these associations before and after the pandemic. Bibliometric data from the web of science core collection (2005-2024) were collected on May 1, 2025, and analyzed using CiteSpace and VOSviewer for literature mapping and visualization. This study included 3571 children and adolescents (6-14 years) from National Health and Nutrition Examination Survey cycles (2013-2016 and 2021-2023) with complete data on serum sex hormones, vitamin D levels, and PA measurements. Pubertal status was determined based on elevated steroid hormone levels. Bibliometric analysis shows that research on precocious puberty has grown significantly in recent years, with focus shifting from early investigations into disease etiology and treatment protocols to new directions such as genetic mechanisms and the impact of COVID-19. Notably, however, studies on PA and vitamin D remain remarkably scarce, with most research on their associations with precocious puberty still at the single-factor analysis level. Association analyses demonstrated significantly lower PA and serum 25(OH)D levels in pubertal versus prepubertal participants. PA levels (odds ratio [OR] = 0.83, 95% CI: 0.80-0.87, P < .001) and 25(OH)D concentrations (OR = 0.98, 95% CI: 0.98-0.99, P < .001) were both significantly negatively associated with pubertal status. 25(OH)D exhibited a nonlinear association with pubertal status, demonstrating a saturation threshold at 72.5 nmol/L beyond which its protective effect was no longer significant. Additionally, 25(OH)D mediated the protective effect of PA against early puberty, with the mediating effect accounting for 7.62%. Analysis of post-COVID-19 pandemic (2021-2023) data showed that after adjusting for metabolic indicators, the PA association disappeared (OR = 0.97, 95% CI: 0.88-1.07, P = .504), while 25(OH)D's inverse correlation with early puberty persisted (OR = 0.98, 95% CI: 0.97-0.99, P < .001). The study demonstrated that both PA and 25(OH)D levels significantly reduced early puberty risk, with 25(OH)D mediating PA's protective effect. Post-pandemic analyses showed the PA association disappeared, while 25(OH)D's inverse correlation with early puberty persisted.