IMPORTANCE One-third of singers and vocal professionals report experiencing a benefit from empirical vitamin B 12 injections for improvement of mild singing-related symptoms (eg, reduced stamina, vocal fatigue, and effort). However, there is no objective evidence to support or refute these claims.OBJECTIVE To assess the presence and magnitude of the effect of empirical vitamin B 12 injection on the vocal performance of singers.
DESIGN, SETTING, AND PARTICIPANTSA randomized, double-blind, placebo-controlled, crossover trial was conducted from November 7, 2017, to November 30, 2018, at an academic voice center among 20 active adult singers without dysphonia but with mild vocal symptoms. Individuals with known or suspected vitamin B 12 deficiency or active or recent vitamin B 12 treatment were excluded. Analysis was on a per-protocol basis.INTERVENTIONS Participants were randomized to receive an intramuscular (deltoid) injection of either vitamin B 12 (1000 μg of cyanocobalmin) or placebo (0.9% sodium chloride). After a washout period of at least 4 weeks, participants were crossed over to receive the opposite injection. Both the investigators and participants were blinded to the order of injections.
MAIN OUTCOMES AND MEASURESThe participants completed the Singing Voice Handicap Index-10 (SVHI-10), the Voice Fatigue Index (VFI), and the Evaluation of the Ability to Sing Easily (EASE) before each injection and at intervals of 1 hour, 3 hours, 24 hours, 72 hours, and 1 week after the injection. The primary time point assessment was 72 hours after injection, and the SVHI-10 score was the primary outcome measure.
RESULTSTwenty singers (10 men; median age, 22 years [range, 19-42 years]) were enrolled. The improvements after either placebo or vitamin B 12 injections were comparable to each other. At 72 hours after the vitamin B 12 injection, the median difference in the SVHI-10 score was 1 (95% CI, -1 to 2) compared with 3 (95% CI, 0-4) after placebo. The median difference between differences at 72 hours between placebo and vitamin B 12 injections were 1.5 (95% CI, -2 to 5) for the SVHI-10, 1 (95% CI, -9 to 9) for the VFI, and -1 (95% CI, -3 to 2) for the EASE. The improvements after both injections failed to reach the estimated minimal clinically important difference. Of the 20 participants, 4 (20%) reached the estimated minimal clinically important difference in their SVHI-10 score after 72 hours for both vitamin B 12 and placebo injections.CONCLUSIONS AND RELEVANCE This randomized, double-blind, placebo-controlled, crossover trial found that after empirical vitamin B 12 injection to improve mild voice-related symptoms, the improvement in self-reported voice measures in singers shows no meaningful difference compared with placebo.TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT03437824