This study investigates the impact of daily versus weekly vitamin D3 supplementation on sleep quality in adults with vitamin D3 deficiency.

Emerging evidence suggests a link between serum vitamin D3 deficiency and poor sleep quality, but the optimal dosing frequency to improve sleep quality remains unclear.

This is a single centre, prospective, double-blinded, randomised controlled trial which has randomised (1:1) Vitamin D3 deficient adults into daily (2000 IU/day for 8 weeks) supplementation group and weekly (60,000 IU/week for 8 weeks) supplementation group.  Subjective sleep quality was evaluated using Pittsburg sleep quality index questionnaire (PSQI) at baseline and 8-weeks follow-up.  Wilcoxan signed rank test and Mann Whitney U test was used to compare both the arms.

This study enrolled 87 patients, with 45 in the weekly arm and 42 in the daily arm. The mean age was 39.26 [11.03] years, and 71% (n=62) were females. At baseline, the mean serum vitamin D3 level in weekly and daily treatment arm was 15.49 (5.87)ng/mL and 17.34 (5.11)ng/mL respectively.  On follow-up, the daily arm showed significant improvements in ‘duration of sleep’ (0.93 [0.65] vs 1.55 [0.75], p=0.002) and ‘daytime dysfunction due to sleep’ (0.67 [0.57] vs 1.11 [1.15], p=0.007).  The weekly arm performed better in the 'need medication to sleep’ parameter (0.13 [0.50] vs 0.37 [0.54], p=0.034). However, the daily supplementation arm showed a favourable PSQI total score when compared to the weekly arm (8.46 [3.14] vs 9.93 [2.68], p=0.024) at 8 weeks follow-up.

Daily vitamin D3 supplementation is more effective to weekly supplementation to improve overall sleep quality, sleep duration and daytime dysfunction in vitamin D3 deficient adults.