Table 2.
Results of included studies.
| First Author, Country | Outcomes Evaluated and Assessment | Baseline 25OHD Level | Endline 25OHD Level | Baseline Outcomes | Endline Outcomes | Conclusion |
|---|---|---|---|---|---|---|
| Randomized, controlled trial | ||||||
| Sleep quality | ||||||
| Ghaderi [25], Iran | Sleep quality: PSQI | I: 13.9 ± 4.5 C: 13.5 ± 4.5 (NS difference between I and C) |
I: 22.0 ± 7.5 (sig. increase) C: 13.1 ± 5.9 |
I: 6.0 ± 2.3 C: 6.6 ± 2.2 |
I: 4.5 ± 2.2 (sig. decrease) C: 6.4 ± 3.0 |
PSQI sig. decreased in VDS I group compared with C group (−1.5 ± 2.2 vs. −0.2 ± 2.3) |
| Maheshwari [41], NR | Sleep quality: PSQI | NR | NR | NR | t-test: 2.965; CI: 1.8312–6.8341; p = 0.004 (sig. differences before and after VDS) | VDS improves sleep in patients with chronic low back pain |
| Majid [27], Iran | Sleep quality: PSQI Sleep duration Sleep latency Sleep efficiency: real sleep duration from the whole time passed in bed Sleep disturbances Use of sleep medications Daytime dysfunction: experiencing problems resulted by sleeplessness Subjective sleep quality |
I: 25.00 ± 8.95 C: 27.60 ± 8.30 (NS difference between I and C) |
I: 37.69 ± 12.25 C: 27.97 ± 7.46 (sig. increase in I, and sig. difference between I and C) |
PSQI (score) (NS difference between I and C) I: 9.45 ± 2.44 C: 10.51 ± 3.14 Sleep duration (hour) (sig. higher in I compared with C) I: 5.83 ± 1.15 C: 5.22 ± 1.54 Sleep latency (minute) (NS difference between I and C) I: 49.88 ± 38.99 C: 65.00 ± 47.54 Sleep efficiency (%) (NS difference between I and C) I: 82.58 ± 9.93 C: 78.20 ± 12.90 Sleep disturbances (score) (NS difference between I and C) I: 1.23 ± 0.47 C: 1.40 ± 0.78 Use of sleep medications (time per week) (NS difference between I and C) I: 2.07 ± 1.92 C: 0.77 ± 1.02 Day time dysfunction (score) (NS difference between I and C) I: 1.57 ± 0.99 C: 1.17 ± 0.93 Subjective sleep quality (score) (NS difference between I and C) I: 1.68 ± 0.77 C: 1.57 ± 0.62 |
PSQI (score) (sig. lower in I compared with C) I: 6.75 ± 2.97 (sig. decrease) C: 9.73 ± 3.04 Sleep duration (hour) (sig. higher in I compared with C) I: 6.50 ± 1.49 C: 5.21 ± 1.44 Sleep latency (minute) (sig. lower in I compared with C) I: 33.18 ± 27.91 C: 58.57 ± 36.81 Sleep efficiency (%) (NS difference between I and C) I: 86.97 ± 11.39 (sig. decrease) C: 80.89 ± 11.46 Sleep disturbances (score) (NS difference between I and C) I: 1.14 ± 0.46 (NS) C: 1.41 ± 0.65 (NS) Use of sleep medications (time per week) (NS difference between I and C) I: 1.07 ± 0.94 (sig. decrease) C: 1.20 ± 0.99 Day time dysfunction (score) (NS difference between I and C) I: 0.70 ± 0.96 (sig. decrease) C: 0.75 ± 0.98 Subjective sleep quality (score) (sig. lower in I compared with C) I: 1.18 ± 0.62 (sig. decrease) C: 1.46 ± 0.58 |
Reduced PSQI (improved sleep score), reduced sleep latency, increased sleep duration, and subjective sleep quality with VDS. NS difference in sleep efficiency, sleep disturbances, and use of sleep medications |
| Mason [28], USA | Sleep quality: PSQI | NR | NR | NR | NR | NS change in overall sleep quality between VDS I and C groups A greater magnitude of change in serum 25(OH)D was associated with an increased need to take medications to sleep and overall worse sleep quality Deterioration in total PSQI among women who became vitamin D replete (≥32 ng/mL) compared with those who remained <32 ng/mL (despite VDS) VDS of 2000 IU/d may result in overall worse sleep quality for postmenopausal women with low circulating vitamin D undergoing weight loss |
| Mirzaei [30], Iran | Sleep quality: PSQI | I: 11.4 ± 6.7 C: 13.4 ± 7.3 |
I: 33.5 ± 12.2 (sig. higher in I compared with C) C: 13.3 ± 7.2 |
I: 10 ± 3.3 C: 10.75 ± 4.4 |
I: 6.2 ± 2.2 C: 8.2 ± 3.7 (sig. lower in I compared with C) |
Considerable improvements were observed in the PSQI score of the both study groups; yet there was a sig. greater decrease in mean PSQI score in the I compared with C group |
| Other outcomes | ||||||
| McCarthy [29], Pacific Northwest | Sleep-related impairment: Questions from the National Institutes of Health Patient-Reported Outcomes Measurement Information System | I1: 22.2 ± 5.0 I2: 22.9 ± 4.7 C: 37.8 ± 5.6 |
I1: 30.80 ± 10.0 I2: 40.15 ± 7.5 (sig. higher in I2 compared with I1 and C) C: 34.46 ± 9.9 |
I1: 53.0 ± 7.0 I2: 48.3 ± 9.5 C: 51.5 ± 7.0 |
I1: 49.5 ± 9.5 I2: 45.2 ± 8.4 C: 49.3 ± 8.2 |
Statistically significant improvements seen across groups and over time |
| Okereke [32], USA | Sleep difficulty (sleep problems) as specific depressive feature (item-level symptom) from the 8 item Patient Health Questionnaire depression scale: Trouble falling or staying asleep, or sleeping too much | 25(OH)D < 20 ng/mL I: 11.0% C: 12.3% Mean ± SD I: 31.2 ± 9.8 C: 31.1 ± 10.0 |
NR | NR | NR | NS differences in likelihood of sleep problems in the I compared with C group Adjusted differences in change in likelihood of PHQ-8 item-level symptoms, comparing vitamin D3 to Placebo: Sleep problems: Likelihood ratio: 95% CI: 1.00 (0.89–1.12) Analyses were from repeated measures logistic regression models, with follow-up time modeled as an indicator; models were controlled for age, sex, and n-3 fatty acid randomization group. Results show likelihood ratios and 95% confidence intervals (95% CIs), which reflect differences in the change in likelihood of burden from each PHQ-8 item-level symptom, comparing vitamin D3 to placebo treatment group. Differences reflect the average effect over all follow-up times since baseline |
| Rorie [33], USA | Nights of hives and sleep interference: from the Urticaria Symptom Severity scores | Mean(SE) C: 37.1(3.4) I: 28.8(2.2) |
Mean(SE) C: 35.8(2.3) I: 56.0(3.9) (sig. higher in I compared with C) |
NR | NR | Beneficial trends for sleep quality and towards decreased interference with sleep were observed with high vitamin D3 |
| Zhu [36], China | Sleep disorder: NR | I: 15.66 ± 4.20 C: 16.86 ± 5.04 (NS difference between I and C group) |
NR | NR | NR | Between-group linear mixed-model analysis showed sig. decrease in Sleep disorder (β: −0.588; 95% CI: −1.061,−0.115), that was rendered NS after controlling for confounding variables (β: −0.355; 95% CI: −0.963,0.227) |
| Kerley [26], Ireland | Sleepiness: ESS | I: 13.38 ± 4.64 C: 16.58 ± 8.81 (NS difference between I and C) |
I: 40.38 ± 15.98 (sig. increase) C: 17.22 ± 8.57 |
I: 11.00 ± 5.00 C: 10.00 ± 6.00 (NS difference between I and C) |
I: 6.00 ± 2.00 C: 7.00 ± 5.00 (NS difference between I and C) |
No difference in ESS between the VDS I group and C group |
| Sharifan [34], Iran | Changes in sleepiness symptoms: Insomnia Severity Index | Milk I: 15.03 ± 3.91 C: 14.9 ± 7.34 (NS difference between I and C group) Yogurt I: 15.82 ± 4.09 C: 16.72 ± 2.96 (NS difference between I and C group) |
Milk: I: 18.57 (sig. increase compared with baseline) C: 14.66 Yogurt: I: 19.93 (sig. increase compared with baseline) C: 16.26 (SD not reported) |
Milk: I: 18.5 ± 3.33 C: 17.25 ± 2.34 Yogurt: I: 13.28 ± 5.12 C: 13 ± 3.54 |
Milk I: 13.62 ± 3.29 (sig. increase compared with baseline) C: 16.5 ± 4.02 (NS difference compared with baseline) Yogurt I: 17.57 ± 13.28 (NS difference compared with baseline) C: 16.66 ± 1.36 (NS difference compared with baseline) |
Fortified low-fat milk containing 1500 IU vitamin D3 can improve insomnia symptoms |
| Wali [35], KSA | RLS severity: IRLSSG rating scale | I: 17.06 ± 12.6 C: 22.95 ± 16.98 (NS difference between I and C group) |
I: 6.09 ± 15.38 (sig. higher in I compared with C group) C: 21.23 ± 13.74 |
Total I: 14.60 ± 4.5 C: 16.11 ± 6.2 In DEF patients I: 14.82 ± 5.2 C: 16.81 ± 6.3 |
Total: I: 14.5 ± 08.2 (NS difference compared with baseline) C: 10.3 ± 11.1 (sig. decrease compared with baseline) In DEF patients I: 13.8 ± 8.9 (NS difference compared with baseline) C: 7.8 ± 13.9 (sig. decrease compared with baseline) |
NS difference in RLS severity score with VDS suggesting that VDS does not improve RLS symptoms |
| Sleep problems as adverse events of VDS | ||||||
| de Koning [24], the Netherlands | Sleep problems as adverse event: registered by telephone or face-to-face contact | median [IQR] I: 18.42 [13.02–22.83] C: 17.68 [14.42–22.13] (significance NR) |
mean ± SD I: 34.05 ± 6.41 C: 17.22 ± 7.21 (sig. difference between I and C) |
NA (sleep problems as adverse event of VDS) | I: n = 1 C: n = 5 (NS difference between I and C) |
NS difference in sleep problems as adverse effect of VDS in community-dwelling people with depressive symptoms |
| Mohammadpour [31], Iran | Sleep problems as adverse events: questionnaire | mean ± SD I: 15.792 ± 5.259 C: 12.979 ± 5.804 (NS difference between I and C) |
mean ± SD: I: 34.63 ± 9.54 (sig. increase between baseline and endline) C: 11.22 ± 5.11 (NS difference between baseline and endline) Sig. difference between I and C |
NA (sleep problems as adverse event of VDS) | Rate I: 4 C: 1 (NS difference between I and C) |
NS difference in sleep problems as adverse effect of VDS as adjunctive therapy in children with ADHD |
| Opportunistic addition to a randomized, controlled trial | ||||||
| Other outcomes | ||||||
| Slow [37], New Zealand | Specific questionnaire about disruptions in sleeping patterns as a consequence of the earthquake on the 22nd February 2011 | I: 29.24 ± 8.81 C: 28.44 ± 8.81 |
NR | NR | I: 79% C: 70% (NS difference between I and C) |
VDS did not reduce the adverse impact of earthquakes in healthy adults |
| Pre–post study | ||||||
| Sleep quality | ||||||
| Eshaghi [39], Iran | Sleep quality: PSQI | NR | NR | Mean ± SD I: 12.55 ± 1.01 C: 12.55 ± 1.01 |
Mean ± SD I: 10.11 ± 1.26 (significant difference compared with baseline) C: 12.44 ± 0.88 (contradictory evidence regarding C group between written (NS difference) and tabulated (sig. difference) results) |
Sleep quality sig. improved by 19.1% with VDS |
| Other outcomes | ||||||
| Guler [40], Turkey | Sleep habits and disorders: short version of the CSHQ with a higher score reflecting more disturbed sleep behavior | Cases: 25(OH)D < 10 ng/mL: 23.3% 25(OH)D: 10–30 ng/mL: 45% 25(OH)D > 30 ng/mL: 31.7% mean ± SD: 25.58 ± 10.31 Controls: 25(OH)D < 10 ng/mL: 23.3% 25(OH)D: 10–30 ng/mL: 38.3% 25(OH)D > 30 ng/mL: 38.3% mean ± SD: 25.35 ± 9.92 (NS difference between Cases and Controls) In DEF participants: 25(OH)D: Cases: 19.68 ± 6.22 Controls: 19.21 ± 7.35 |
Cases: 25(OH)D < 10 ng/mL: 0% 25(OH)D: 10–30 ng/mL: 11.7% 25(OH)D > 30 ng/mL): 88.3% mean ± SD: 37.27 ± 6.51 Controls: 25(OH)D < 10 ng/mL: 0% 25(OH)D: 10–30 ng/mL: 6.7% 25(OH)D > 30 ng/mL: 93.3% mean ± SD: 37.15 ± 6.78 (NS difference between Cases and Controls) In DEF participants: 25(OH)D: Cases: 37.26 ± 7.34; sig Controls: 39.13 ± 7.74; sig |
CSHQ total score Cases: <41: 21.7%; ≥41: 78.3% Controls: <41: 66.7%; ≥41: 33.3% mean ± SD total sleep time (hours) Cases: 8.10 ± 0.97 Controls: 9.24 ± 0.89 In DEF participants Total score Cases: 52.05 ± 8.24 Controls: 42.00 ± 4.78 Bedtime resistance Cases: 11.24 ± 2.49 Controls: 7.38 ± 1.01 Sleep-onset delay Cases: 2.32 ± 0.79 Controls: 1.86 ± 0.89 Sleep duration Cases: 5.41 ± 0.92 Controls: 4.41 ± 0.98 Sleep anxiety Cases: 7.73 ± 2.59 Controls: 4.41 ± 0.80 Night wakings Cases: 5.59 ± 1.61 Controls: 4.11 ± 1.39 Parasomnias Cases: 9.80 ± 2.52 Controls: 8.51 ± 1.76 Sleep-disordered breathing Cases: 3.63 ± 0.73 Controls: 3.59 ± 0.90 Daytime sleepiness Cases: 10.44 ± 1.84 Controls: 9.89 ± 1.85 Total sleep time Cases: 8.16 ± 0.89 Controls: 9.11 ± 0.89 |
CSHQ total score Cases: <41: 28.3%; ≥41: 71.7% Controls: <41: 86.7%; ≥41: 13.3% mean ± SD total sleep time (hours) Cases: 8.58 ± 0.96 Controls: 9.38 ± 0.88 (sleep time sig. different between Cases and Controls) In DEF participants Total score Cases: 46.43 ± 8.04; sig Controls: 37.56 ± 2.80; sig Bedtime resistance Cases: 10.17 ± 2.66; sig Controls: 7.21 ± 0.75; NS Sleep-onset delay Cases: 1.82 ± 0.80; sig Controls: 1.08 ± 0.36; sig Sleep duration Cases: 4.70 ± 0.95; sig Controls: 4.18 ± 0.90; sig Sleep anxiety Cases: 6.78 ± 2.35; sig Controls: 4.05 ± 0.4; sig Night wakings Cases: 4.24 ± 1.59; sig Controls: 3.32 ± 0.62; sig Parasomnias Cases: 8.75 ± 1.84; sig Controls: 7.16 ± 0.44; sig Sleep-disordered breathing Cases: 3.41 ± 059; sig Controls: 3.40 ± 0.76; sig Daytime sleepiness Cases: 10.17 ± 1.93; NS Controls: 9.21 ± 1.08; sig Total sleep time Cases: 8.63 ± 0.85; sig Controls: 9.29 ± 0.89; sig |
VDS may be beneficial in ASD patients and healthy individuals with sleep disturbances |
| Arico [38], Italy | RLS severity: IRLS-RS | 10.3 | 30.4 (no information on statistical significance) | 19.8 | 8.6 (no information on statistical significance) | VDS has a therapeutic effect in decreasing RLS severity |
| Pre–post study, analyzed retrospectively as a case series | ||||||
| Sleep quality | ||||||
| Huang [42], USA | Sleep quality: PSQI Sleep latency: #2 “how long has it usually taken you to fall asleep each night” of the PSQI Sleep duration: #4 “how many hours of actual sleep did you get at night” of the PSQI Sleep efficiency: #4 + #1 “what time have you usually gone to bed at night” + #3 “what time have you usually gotten up in the morning” of the PSQI |
Total: 18.57 ± 5.42 INS: 22.73 ± 1.83 DEF: 13.77 ± 3.94 |
Total: 26.00 ± 8.38 (sig. increase) INS: 29.60 ± 11.67 DEF: 24.00 ± 5.79 |
Global PSQI score Total: 13.46 ± 4.92 INS: 12.27 ± 5.55 DEF: 14.85 ± 3.83 Sleep latency (min) Total: 67.22 ± 56.13 INS: 41.61 ± 48.21 DEF: 94.81 ± 52.15 Sleep duration (h) Total: 4.59 ± 1.84 INS: 5.33 ± 1.88 DEF: 3.73 ± 1.41 Sleep efficiency (%) Total: 59.79 ± 25.31 INS: 66.97 ± 23.7 DEF: 52.61 ± 25.70 |
Global PSQI score Total: 12.22 ± 4.61 (sig. decrease) INS: 11.29 ± 4.66 DEF: 13.23 ± 4.51 (sig. decrease) Sleep latency (min) Total: 57.86 ± 44.03 (sig. decrease) INS: 39.83 ± 39.05 DEF: 78.65 ± 41.33 (sig. decrease) Sleep duration (h) Total: 5.30 ± 1.57 (sig. decrease) INS: 5.90 ± 1.55 (sig. decrease) DEF: 4.62 ± 1.33 (sig. decrease) Sleep efficiency (%) Total: 66.62 ± 18.61 (sig. increase) INS: 70.34 ± 17.76 DEF: 62.33 ± 19.34 (sig. increase) |
Sig. improvement in overall sleep quality, sleep latency, sleep duration, and sleep efficiency in veterans with multiple areas of chronic pain with VDS (after controlling for potential confounders improvement in sleep efficiency became borderline significant) The magnitudes of sleep improvement in latency, duration, and efficiency were all larger in the DEF subgroup; however, the difference in improvements between the subgroups was NS except for sleep latency |
I: intervention; C: control; PSQI: Pittsburgh Sleep Quality Index; NR: not reported; INS: insufficient; DEF: deficient; VDS: vitamin D supplementation; 25(OH)D: 25-hydroxyvitamin D; SD: Standard Deviation; NS: Not Significant; sig. Significant; IU: International Unit; ESS: Epworth Sleepiness Scale; NR: not reported; RLS: restless legs syndrome; IRLSSG: International Restless Legs Syndrome Study Group; CI: confidence interval; IRLS-RS: International Restless Legs Syndrome Rating Scale; ADHD: Attention Deficit Hyperactivity Disorder; IQR: Interquartile Range; ASD: Autism Spectrum Disorder; CSHQ: Children’s Sleep Habits Questionnaire IRLS-RS: International Restless Legs Syndrome Rating Scale; IRLSSG: International Restless Legs Syndrome Study Group; CSHQ: Children’s Sleep Habits Questionnaire; PHQ-8 Item: The 8 item Patient Health Questionnaire depression scale; NA: Not Applicable; SE: Standard Error.