Vitamin D Supplementation and Improvement in Insomnia Symptoms Among Malaysian Women With Vitamin D Deficiency: Protocol for a Randomized Controlled Trial.

Background: Insomnia is a prevalent sleep disorder associated with adverse physical, psychological, and functional outcomes. Emerging evidence suggests that vitamin D deficiency may contribute to sleep disturbances. Women are more likely to have lower serum vitamin D (25-hydroxyvitamin D [25(OH)D]) levels than men, and they also report a higher prevalence of insomnia. Although several studies have proposed that vitamin D supplementation may improve insomnia symptoms, findings remain inconsistent, and evidence from Southeast Asian populations is limited. Objective: This study aims to evaluate the effectiveness of weekly vitamin D₃ supplementation in improving insomnia symptoms, sleep quality, sleep efficiency, and functional outcomes among Malaysian women with vitamin D deficiency. Methods: This study is a double-blind, parallel-group, randomized placebo-controlled trial conducted among women aged 19-50 years with serum 25(OH)D levels <20 ng/mL and insomnia symptoms. Participants are randomized to receive either vitamin D₃ capsules (50,000 IU/wk) or placebo (1 capsule/wk) for 9 weeks. The study is conducted in a community setting. Primary outcomes include insomnia severity assessed using the Insomnia Severity Index (ISI), sleep quality measured by the Pittsburgh Sleep Quality Index (PSQI), and sleep efficiency objectively assessed using actigraphy. Secondary outcomes include daytime sleepiness measured using the Epworth Sleepiness Scale (ESS) and functional outcomes assessed using the Functional Outcomes of Sleep Questionnaire (FOSQ-10). Assessments are conducted at baseline, midintervention, and postintervention. Results: Participant recruitment commenced in December 2023 and is expected to conclude in December 2026. As of July 2026, 42 participants had been screened, 33 eligible participants had been enrolled, 22 had completed the study procedures, 4 were in the intervention phase, and 1 had withdrawn due to loss of contact. Conclusions: If the efficacy of vitamin D3 supplementation in alleviating insomnia symptoms is demonstrated, it might be proposed as a supplementary approach to cognitive behavioral therapy (CBT) for insomnia. Screening for vitamin D deficiency may also be considered in individuals presenting with insomnia symptoms prior to initiating pharmacological treatment.