Reporting of background | |
√ | Problem definition | The Mediterranean diet is associated with decreased morbidity and mortality from various chronic diseases. Adherence to a Mediterranean-style diet has been suggested to have protective effects on bone health and decreases the incidence of bone fractures, but the evidence is not clear. We conducted a systematic review and meta-analysis of available observational studies to quantify the association between adherence to a Mediterranean-style diet, as assessed by the Mediterranean Diet Score (MDS), and the risk of fractures in the general population |
√ | Hypothesis statement | Adherence to a Mediterranean-style diet is associated with decreased risk of fractures |
√ | Description of study outcomes | Any fractures |
√ | Type of exposure | Adherence to a Mediterranean-style diet |
√ | Type of study designs used | Longitudinal studies (prospective or retrospective case–control, prospective cohort, retrospective cohort, case-cohort, nested case–control, or clinical trials) |
√ | Study population | Participants based in general populations in whom adherence to a Mediterranean-style diet has been assessed and have been followed-up for fracture outcomes |
Reporting of search strategy should include | |
√ | Qualifications of searchers | Setor Kunutsor, PhD; Jari Laukkanen, PhD |
√ | Search strategy, including time period included in the synthesis and keywords | Time period: from inception to October, 2016 The detailed search strategy can be found in Appendix 3 |
√ | Databases and registries searched | MEDLINE, EMBASE, and Web of Science, and Cochrane databases |
√ | Search software used, name and version, including special features | OvidSP was used to search EMBASE and MEDLINE EndNote used to manage references |
√ | Use of hand searching | We searched bibliographies of retrieved papers |
√ | List of citations located and those excluded, including justifications | Details of the literature search process are outlined in the flow chart in Appendix 5 |
√ | Method of addressing articles published in languages other than English | We placed no restrictions on language |
√ | Method of handling abstracts and unpublished studies | Not applicable |
√ | Description of any contact with authors | Not applicable |
Reporting of methods should include | |
√ | Description of relevance or appropriateness of studies assembled for assessing the hypothesis to be tested | Detailed inclusion and exclusion criteria are described in the “ Methods” section |
√ | Rationale for the selection and coding of data | Data extracted from each of the studies were relevant to the population characteristics, study design, exposure, and outcome |
√ | Assessment of confounding | We assessed confounding by ranking individual studies on the basis of different adjustment levels and performed subgroup analyses to evaluate differences in the overall estimates according to levels of adjustment |
√ | Assessment of study quality, including blinding of quality assessors; stratification or regression on possible predictors of study results | Study quality was assessed based on the nine-star Newcastle–Ottawa Scale using pre-defined criteria namely: population representativeness, comparability (adjustment of confounders), ascertainment of outcome |
√ | Assessment of heterogeneity | Heterogeneity of the studies was quantified with I2 statistic that provides the relative amount of variance of the summary effect due to the between-study heterogeneity and explored using meta-regression and stratified analyses |
√ | Description of statistical methods in sufficient detail to be replicated | Description of methods of meta-analyses, sensitivity analyses, meta-regression, and assessment of publication bias are detailed in the methods. We performed random effects meta-analysis with Stata 14 |
√ | Provision of appropriate tables and graphics | Table and Figure |
Reporting of results should include | |
√ | Graph summarizing individual study estimates and overall estimate | Figure |
√ | Table giving descriptive information for each study included | Table |
√ | Results of sensitivity testing | Sensitivity analysis was conducted to assess the influence of some large studies and low-quality studies on the pooled estimate. This was done by omitting such studies and calculating a pooled estimate for the remainder of the studies |
√ | Indication of statistical uncertainty of findings | 95% confidence intervals were presented with all summary estimates, I2 values and results of sensitivity analyses |
Reporting of discussion should include | |
√ | Quantitative assessment of bias | Sensitivity analyses indicate heterogeneity in strengths of the association due to most common biases in observational studies. The systematic review is limited in scope, as it involves limited number of studies |
√ | Justification for exclusion | All studies were excluded based on the pre-defined inclusion criteria in methods section |
√ | Assessment of quality of included studies | Brief discussion included in ‘Methods’ section |
Reporting of conclusions should include | |
√ | Consideration of alternative explanations for observed results | Discussion |
√ | Generalization of the conclusions | Discussed in the context of the results |
√ | Guidelines for future research | We recommend well-designed observational studies as well as clinical trials |
√ | Disclosure of funding source | Not applicable |