CLINICAL INVESTIGATIONS Effect of Vitamin D Supplementation on Muscle Strength, Gait and Balance in Older Adults: A Systematic Review and Meta-Analysis

s were screened to identify potentially relevant articles. After retrieving the full text, an article was considered relevant if it met the following criteria: randomized controlled trial of supplemental vitamin D or associated metabolite, with or without calcium, with a placebo or standard treatment arm; study did not include an exercise intervention; study population consisted of older adults, age 60 and older; and physical performance measures of muscle strength, gait, or balance were measured at baseline and study termination. The two authors independently evaluated each article to determine whether it met the inclusion criteria for full review. Methodological Quality Assessment The two authors independently assessed the methodological quality of included articles using the Downs and Black scale, a validated, reliable instrument for evaluating clinical trials. The scale has 27 questions grouped into five sections: reporting; external validity; internal validity, bias; internal validity, confounding; and power. The aggregated maximum possible score is 32, with a higher score indicating greater methodological quality. When rating discrepancies occurred, the two reviewers resolved differences by consensus to achieve a single score. The quality of reporting was evaluated using the CONSORT guidelines. Interrater reliability of the methodological assessment of the ratings in this study, using the intraclass correlation coefficient (ICC), were 0.87 for the Downs and Black score and 0.85 for the CONSORT score.