Use of GRADE in systematic reviews of health effects on pollutants and extreme temperatures: A cross-sectional survey

Maternal exposure to ambient air temperature and adverse birth outcomes: An umbrella review of systematic reviews and meta-analyses

BACKGROUND

Multiple systematic reviews on prenatal ambient temperature and adverse birth outcomes exist, but the overall epidemiological evidence and the appropriate metric for thermal stress remain unclear. An umbrella review was performed to summarise and appraise the evidence with recommendations.

METHODS

Systematic reviews and meta-analyses on the associations between ambient temperature and adverse birth outcomes (preterm birth, stillbirth, birth weight, low birth weight, and small for gestational age) up to December 20, 2023, were synthesised according to a published protocol. Databases PubMed, CINAHL, Scopus, MEDLINE/Ovid, EMBASE/Ovid, Web of Science Core Collection, systematic reviews repositories, electronic grey literature, and references were searched. Risk of bias was assessed using Joanna Briggs Institute's critical appraisal tool.

RESULTS

Eleven systematic reviews, including two meta-analyses, were included. This comprised 90 distinct observational studies that employed multiple temperature assessment metrics with a very high overlap of primary studies. Primary studies were mostly from the United States while both Africa and South Asia contributed only three studies. A majority (7 out of 11) of the systematic reviews were rated as moderate risk of bias. All systematic reviews indicated that maternal exposures to both extremely high and low temperatures, particularly during late gestation are associated with increased risks of preterm birth, stillbirth, and reduced fetal growth. However, due to great differences in the exposure assessments, high heterogeneity, imprecision, and methodological limitations of the included systematic reviews, the overall epidemiological evidence was classified as probable evidence of causation. No study assessed biothermal metrics for thermal stress.

CONCLUSIONS

Despite the notable methodological differences, prenatal exposure to extreme ambient temperatures, particularly during late pregnancy, was associated with adverse birth outcomes. Adhering to the appropriate systematic review guidelines for environmental health research, incorporating biothermal metrics into exposure assessment, evidence from broader geodemographic settings, and interventions are recommended in future studies.

Author instructions in biomedical journals infrequently address systematic review reporting and methodology: a cross-sectional study

OBJECTIVES

We aimed to analyze how instructions for authors in journals indexed in MEDLINE address systematic review (SR) reporting and methodology.

STUDY DESIGN AND SETTING

We analyzed instructions for authors in 20% of MEDLINE-indexed journals listed in the online catalog of the National Library of Medicine on July 27, 2021. We extracted data only from the instructions published in English. We extracted data on the existence of instructions for reporting and methodology of SRs.

RESULTS

Instructions from 1,237 journals mentioned SRs in 45% (n = 560) of the cases. Systematic review (SR) registration was mentioned in 104/1,237 (8%) of instructions. Guidelines for reporting SR protocols were found in 155/1,237 (13%) of instructions. Guidelines for reporting SRs were explicitly mentioned in 461/1,237 (37%), whereas the EQUATOR (Enhancing the Quality and Transparency of Health Research) network was referred to in 474/1,237 (38%) of instructions. Less than 2% (n = 20) of instructions mentioned risk of bias and meta-analyses; less than 1% mentioned certainty of evidence assessment, methodological expectations, updating of SRs, overviews of SRs, or scoping reviews.

CONCLUSION

Journals indexed in MEDLINE rarely provide instructions for authors regarding SR reporting and methodology. Such instructions could potentially raise authors' awareness and improve how SRs are prepared and reported.