Table 1.
Characteristics of randomized controlled clinical trials included in the present systematic review.
|
First author Publication year Country |
Number and gender distribution (f/m) in each group | Study design | Mean age of each group at the baseline (years) | Baseline serum zinc levels (mg/L) | Dietary zinc intake (mg/day) | Duration of intervention (weeks) | Dose | Intervention group | Comparison group | Notes about participant | Outcomes | Main outcome results |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Afzali et al. 18 Iran |
T:150 IN:75 M:29 F:46 C:75 M:18 F:57 |
Parallel randomized clinical trial |
IN: 66.8 ± 7.1 C: 66.1 ± 5.8 |
IN: 65.1 ± 17.1 C: 68.6 ± 10.1 |
NR | 10 weeks | 30 mg/day as zinc | Zinc supplementation | No receive any supplementation | Older Adults | PSQI | The quality of sleep in the intervention group improved significantly in all of the PSQI domains compared to the control group. Also, there was a significant and negative correlation between sleep quality scores and serum zinc levels after the intervention. |
|
Haddadian‐Khouzani et al. 17 Iran |
T:75 IN:38 M:26 F:12 C:37 M:24 F:13 |
Parallel double‐blind randomized clinical trial |
IN: 49.23 ± 15.35 C: 51.21 + 13.76 |
IN: 81.9 ± 16.8 C: 82.3 ± 18.2 |
IN: 9.2 ± 3.5 C: 8.1 ± 3.4 |
12 weeks | 30 mg/day zinc gluconate | zinc gluconate supplementation | Placebo | Haemodialysis patients | PSQI | The quality of sleep in the group supplemented with zinc improved significantly compared to the control group. |
|
Marrero et al. 23 Spain |
T:50 IN:24 C:26 Gender distribution was not reported |
Randomized, Double‐Blind, Placebo‐Controlled Trial |
IN: 51.0 ± 10.2 C: 53.7 ± 9.6 |
IN: 122.0 ± 6.3 C: 114.7 ± 3.9 |
NR | 16 weeks | 10 mg/day ZINC +1Mg melatonin | ZINC supplementation +melatonin | Placebo | ME/CFS patients | PSQI | There was no significant change in any of the domains of PSQI in the intervention group compared to the control group. |
|
Jafari et al. 22 Iran |
57 IN:27 C:30 |
Randomized, double‐blind, placebo‐controlled trial |
IN: 23.04 ± 2.97 C: 22.53 ± 1.85 |
IN: 75.5 ± 11.7 C: 85.5 ± 26.7 |
IN: 7.8 ± 1.1 C: 8.00 ± 0.9 |
12 weeks | 30 mg/day of elemental zinc | Zinc gluconate tablets | Placebo | Young women with premenstrual syndrome aged 18–30 years old | PSQ | No significant change was detected in the sleep quality of the supplemented group compared to the control group. |
|
Gholipour Baradari et al. 16 Iran |
T:53 IN:27 M:3 F:24 C:26 M:1 F:25 |
Double Blinded Randomized Controlled Trial |
IN: 30.93 ± 5.48 C: 31.5 ± 5.46 |
IN: 60.1 ± 16.5 C: 59.6 ± 16.6 |
NR | 4 weeks | 220 mg zinc sulfate capsules every 72 h | Zinc sulfate capsules | Placebo | ICU Nurses |
PSQI Poor Sleep Proportion |
The quality of sleep in the group supplemented with zinc improved significantly compared to the control group. However, there was no significant difference in the poor sleep proportion changes between the two groups. |
|
KIM et al. 21 Korea |
T:41 IN:22 M:13 F:9 C:19 M:8 F:11 |
randomized clinical trial |
IN: 5.36 ± 3.03 C: 5.89 ± 2.03 |
IN: 96.3 ± 9.3 C: 93.3 ± 6.5 |
NR | 8 weeks | 12 mg/day as zinc | Zinc oxide tablets + oral antihistamines + topical moisturizers | Antihistamines + topical moisturizers | Atopic Dermatitis Children patients with low hair zinc levels | VAS score for sleep disturbance | There was no significant change in VAS scores for sleep disturbance in the zinc supplementation group compared to the control group. |
|
Ranjbar et al. 20 Iran |
T:38 IN:21 M:1 F:20 C:17 M:3 F:14 |
Double blind randomized clinical trial |
IN: 37 ± 9 C: 37.5 ± 8 |
IN: 100 ± 15 C: 106 ± 17 |
IN: 6.5 ± 2.1 C: 7.6 ± 2.2 |
12 weeks | 25 mg zinc/day | Zinc + SSRIs | Placebo + SSRIs | Patients with Major Depression aged 18‐55 years | Sleep duration (hours per day) | During the intervention, there was no significant change in the sleep duration of the zinc supplementation group compared to the control group. |
|
Kordas et al. 19 USA A |
T:434 IN:219 M:103 F:116 C:215 M:108 F:107 |
Randomized, placebo‐controlled trials |
IN: 12.9 ± 3.9 (M) C: 12.1 ± 3.8 (M) |
NR | NR | 12 months | 10 mg/day elemental zinc(Infants less than 1 year old received half of this dose) | Zinc supplementation | Placebo | Infants from Zanzibar | Maternal Reports of infants Sleep patterns | Zinc supplementation had no significant impact on total sleep duration compared to the control group. |
|
Kordas et al. 19 USA B |
T:277 IN:125 M:52 F:73 C:152 M:70 F:82 |
Randomized, placebo‐controlled trials |
IN: 10.4 ± 4.2 (M) C: 11.2 ± 4.1 (M) |
NR | NR | 12 months | 10 mg/day elemental zinc(Infants less than 1 year old received half of this dose) | Zinc supplementation | Placebo | Infants from Nepal | Maternal Reports of infants Sleep patterns | Zinc supplementation significantly increased the total sleep duration compared to control group. |
Note: Bolds indicates number of participants in each of the intervention (IN) and control (C) groups.
Abbreviations: IN, intervention; C, control; M, male; F, female; T, total; IN, intervention group; C, control groups; M, males; F, females; USA, united states of America; U.K, United Kingdom, NR, not reported; VAS, Visual analog scales; ME/CFS, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome; M, months.