Key findings of recent examples of systematic reviews
| Topic | Key points from main results and authors’ conclusions (emphases added) |
| Interventions to reduce ambient particulate matter air pollution and their effect on health | ‘The evidence base, comprising non‐randomized studies only, was of low or very low certainty(…)Given the heterogeneity across interventions, outcomes, and methods, it was difficult to derive overall conclusions(…)The evidence base highlights the challenges related to establishing a causal relationship between specific air pollution interventions and outcomes(…)Researchers should strive to sufficiently account for confounding, assess the impact of methodological decisions(…)and improve the reporting of methods, and other aspects of the study, most importantly the description of the intervention and the context in which it is implemented.’(S2) |
| Fortification of staple foods with vitamin A for vitamin A deficiency | ‘We are uncertain whether fortifying staple foods with vitamin A alone makes little or no difference for serum retinol concentration(…)It is uncertain whether vitamin A alone reduces the risk of subclinical vitamin A deficiency(…)The certainty of the evidence was mainly affected by risk of bias, imprecision and inconsistency.’(S3) |
| Nutritional interventions for preventing stunting in children living in urban slums in low‐ and middle‐income countries | ‘Overall, the evidence was complex to report, with a wide range of outcome measures reported(…)The certainty of evidence was very low to moderate(…)All the nutritional interventions reviewed had the potential to decrease stunting(…)however, there was no evidence of an effect of the interventions included in this review(…)More evidence is needed of the effects of multi‐sectorial (sic) interventions(…)as well as the effects of 'up‐stream' practices and policies’(S4) |
| Environmental interventions to reduce the consumption of sugar‐sweetened beverages and their effects on health | ‘We judged most studies to be at high or unclear risk of bias in at least one domain, and most studies used non‐randomised designs(…)Implementation should be accompanied by high‐quality evaluations using appropriate study designs, with a particular focus on the long‐term effects of approaches suitable for large‐scale implementation.’(S5) |
| Fortification of wheat and maize flour with folic acid for population health outcomes | ‘Most studies had unclear risk of bias(…)Limitations of this review were the small number of studies and participants, limitations in study design, and low‐certainty of evidence due to how included studies were designed and reported.’(S6) |
Source: The five most recently published systematic reviews listed on the website of the Cochrane Public Health Group (http://ph.cochrane.org/cph-reviews-and-topics, accessed 4 July 2019). Citations in this table refer to the online supplementary reference list.