Vitamin D and the Risk of Stress Fracture: A Systematic Review and Meta-Analysis of Case-Control and Cohort Studies

Research Type: Level 1 - Randomized controlled trial (RCT), Meta-analysis of randomized trials with homogeneous results Introduction/Purpose: Background: A stress fracture is an overuse injury to the bone caused by repetitive, submaximal forces that gradually exceed the bone’s natural capacity for self-repair and several biological and mechanical risk factors influence its occurrence. Given the role of vitamin D in bone health, the potential relationship between this micronutrient and stress fractures is of great importance and warrants further investigation. Hypothesis/Purpose: This study aims to establish an association between lower vitamin D status and a higher risk of stress fractures Methods: This systematic review and meta-analysis was conducted and reported according to the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Systematic search was performed without date restriction until June 2024. After the selection process, 7 studies (9 trials and 797 subjects) were included. Risk of bias assessment was performed by independent reviewers using the Newcastle-Ottawa Scale (NOS) (Wells et al., 2021). Mean and standard deviation results of the variables of interest were obtained from the included studies. I2 statistic was used to evaluate the heterogeneity of the studies included in the meta-analysis. The effect size (ES) Cohen’s or Hedges’ was calculated for all studies. The weighted mean of the ES was calculated based on the differences in sample sizes. The unweighted mean ES was also calculated and associated with a 95 % CI. The Cohen classification was used to assess the magnitude of the ES. Results: 8500 articles were identified through the database and references. After removing duplicates and excluding articles that did not meet eligibility criteria according to their titles, abstracts and full texts, 7 studies were selected for inclusion in the systematic review and meta-analysis A total of 7 studies (9 trials and 797 subjects) were included in the meta-analysis. Pooling data from 9 trials that evaluated the influence of serum vitamin D on stress fracture incidence, the meta-analysis revealed that subjects diagnosed with stress fractures had lower vitamin D levels, with a small effect size (-0.23; 95% CI: [-0.32, -0.13]; p = 0.01). The fixed-effects analysis showed no heterogeneity between the studies (I 2 = 0.00%, Q = 12.29, df = 8, p = 0.14) Conclusion: In summary, the results clearly show a correlation between a lower vitamin D status and a higher incidence of stress fractures. Thus, serum vitamin D should be evaluated when dealing with patients with a higher risk of presenting a stress fracture, since it may be an important measure in order to determine prevention and therapeutic approaches