Although most studies were of acceptable methodological quality, the overall certainty of evidence is low. The findings are based mainly on observational, cross-sectional studies with heterogeneity in design and outcome measures. The evidence is further limited by potential bias, confounding, imprecision, and reliance on self-reported data. Longitudinal and interventional studies are needed to confirm causality and clarify underlying mechanisms.
| Reference | Study type | Population | Intervention and comparison | Outcomes | Risk of bias [Table «Additional comments for included studies...»2 Additional comments] |
|---|---|---|---|---|---|
| RCT=randomized controlled trial; SR=systematic review; MA=meta-analysis | |||||
| «Arab A, Lempesis IG, Garaulet M, et al. Sleep and ...»1 | SR, MA | Children, adults general population |
observational studies. | The association between sleep duration, sleep quality, and chronotype with the Mediterranean diet. Sleep duration and quality were assessed using the Pittsburgh sleep quality index (PSQI) and open questions. | Moderate |
| «Arab A, Karimi E, Garaulet M, et al. Dietary patte...»2 | SR, MA | among the general population, China, Finland, France, Greece, Iran, Italy, Japan, Jordan, Korea, Mexico, Poland, Spain, Sweden, Turkey, the United States | observational studies | the association between dietary patterns and insomnia symptoms (as difficulty initiating sleep, maintaining sleep, and/or early morning awakening). | Moderate |
| «Pourmotabbed A, Awlqadr FH, Mehrabani S, et al. Ul...»3 | SR, MA | Adults, adolescents. France, Iran, Brazil, Mexico. |
cross-sectional studies | The association between ultra-processed foods and the risk of insomnia | Moderate |
| «Shahdadian F, Boozari B, Saneei P. Association bet...»4 | SR, MA | Children, adults | cross-sectional studies | the relation between short sleep duration and sugar and sugar-sweetened beverages intake | Moderate |
| «Nadeem IM, Shanmugaraj A, Sakha S, et al. Energy D...»5 | SR, MA | Children, adults. Asia, USA, Europe, Australia, Middle East |
cross-sectional and RCT studies | To evaluate the adverse effects (i.e. insomnia) of energy drink consumption | Moderate |
| Reference | Comments |
|---|---|
| «Arab A, Lempesis IG, Garaulet M, et al. Sleep and ...»1 | The nature of studies, variable quality of the data increase the risk of bias. |
| «Arab A, Karimi E, Garaulet M, et al. Dietary patte...»2 | The nature of studies, variable quality of the data increase the risk of bias. Occurrence of insomnia syndrome was assessed by Insomnia severity index (ISI), Athens insomnia scale (AIS), Women's health initiative insomnia rating scale (WHIIRS), European organization for research and treatment of cancer quality of life questionnaire core 30 (EORTC QLQ-C30), Menopause rating scale (MRS), Jenkins sleep questionnaire (JSQ) and Duke structured interview for sleep disorders (DSISD). |
| «Pourmotabbed A, Awlqadr FH, Mehrabani S, et al. Ul...»3 | The nature of studies, variable UPF definition. |
| «Shahdadian F, Boozari B, Saneei P. Association bet...»4 | The nature of studies, variable quality of the data increase the risk of bias. Short (vs. optimal) sleep duration in adults was associated with a 58% higher intake of energy drinks. Occurrence of insomnia syndrome was assessed by DSM-V and ICSD-3, ISI, Study questionnaire. |
| «Nadeem IM, Shanmugaraj A, Sakha S, et al. Energy D...»5 | The nature of studies. Assesment of the occurrence of insomnia syndrome was not reported. |
Results
| Reference | Number of studies and number of patients (I/C) | Absolute number of events (%) I | Absolute number of events (%) C | Relative effect (95% CI) |
|---|---|---|---|---|
| Level of evidence: very low * Statistically significant The quality of evidence is downgraded due to (study limitations, inconsistency, indirectness, imprecision, publication bias). The quality of evidence in upgraded due to large or very large effects, dose-response gradient, effect of plausible residual confounding). |
||||
| «Arab A, Karimi E, Garaulet M, et al. Dietary patte...»2 | High-quality diet (highest vs. lowest adherence) 6 studies total 18988 |
N/A | N/A | OR 0.66 * (0.48–0.90) [very low] |
| Mediterranean diet (highest vs. lowest adherence) 10 studies total 13511 |
N/A | N/A | OR 0.86 * (0.79–0.93) [very low] |
|
| DASH (highest vs. lowest adherence) 3 studies total 909 |
N/A | N/A | OR 1.01 (0.94-1.07) [very low] |
|
| «Pourmotabbed A, Awlqadr FH, Mehrabani S, et al. Ul...»3 | Ultraprocessed food consumption (higher vs. lower)
7 studies total 159427 |
N/A | N/A | OR 1.53 * (1.20–1.95) [very low] |
| «Nadeem IM, Shanmugaraj A, Sakha S, et al. Energy D...»5 | Energy drinks 4 studies 63/63 |
N/A | N/A | OR 5.02 * (95 % CI 1.72–14.63) [low] |
High-quality diet was estimated via the healthy eating index; highest vs. lowest adherence= Comparisons were made between people with the highest adherence to any specific dietary patterns and those with the lowest adherence; DASH=Dietary Approaches to Stop Hypertension diet is rich in fruits, vegetables, whole grains, lean proteins, and low-fat dairy, while limiting salt, saturated fats, sugar, and red meat. The Mediterranean diet is rich in vegetables, fruits, whole grains, legumes, nuts, fish, and olive oil. Ultraprocessed food defined as heavily industrially processed items containing artificial additives and high levels of sugar, fat, or salt with low nutritional fiber.
| Reference | Number of studies and number of patients (I/C) | Absolute number of events (%) I | Absolute number of events (%) C | Relative effect (95% CI) |
|---|---|---|---|---|
| Level of evidence: very low The quality of evidence is downgraded due to (study limitations, inconsistency, indirectness, imprecision, publication bias). The quality of evidence in upgraded due to large or very large effects, dose-response gradient, effect of plausible residual confounding) I= intervention; C=comparison; CI=confidence interval |
||||
| «Arab A, Lempesis IG, Garaulet M, et al. Sleep and ...»1 | Mediterranea diet score (Insufficient vs. good -quality sleep) 13 studies overall 29 614 |
N/A | N/A | OR 1.38 * (1.10–1.73) very low |
| Reference | Number of studies and number of patients (I/C) | Absolute number of events (%) I | Absolute number of events (%) C | Relative effect (95% CI) |
|---|---|---|---|---|
| Level of evidence: low The quality of evidence is downgraded due to (study limitations, inconsistency, indirectness, imprecision, publication bias). The quality of evidence in upgraded due to large or very large effects, dose-response gradient, effect of plausible residual confounding). I= intervention; C=comparison; CI=confidence interval |
||||
| «Arab A, Lempesis IG, Garaulet M, et al. Sleep and ...»1 | Mediterranea diet score (insufficient vs. sufficient sleep duration) 13 studies total 227151 |
N/A | N/A | OR 1.39 * (1.04–1.85) low |
| «Shahdadian F, Boozari B, Saneei P. Association bet...»4 | Soda intake (adults) (low vs. optimal sleep duration) 2 studies total 20566 |
N/A | N/A | OR 1.20 * (1.12–1.28) moderate |
| Energy drinks intake (adults) (low vs. optimal sleep duration) 2 studies total 3641 |
N/A | N/A | OR 1.58 * (1.31–1.90) low |
|