Database coverage of primary studies included in evidence syntheses on climate-health

Background
High-quality evidence syntheses (ES) on climate-health are vital for policy making. To inform ES search methods it is important to assess the relevance of literature databases for this topic.

Objectives
Our aim was to assess the database coverage of a comprehensive set of primary studies included in published ES on climate-health. We investigated their coverage in PubMed and assessed if studies not indexed in PubMed were available in the Global Health database.

Methods
We searched for climate-health related ES in MEDLINE, Embase, CINAHL, Cochrane Library and ProQuest Dissertations and Theses in February 2021. The search yielded 8614 records after deduplication. 110 climate-health related ES were identified. We extracted all primary studies from the first 79 ES, sorted by number of included studies. As climate change impacts human health via several pathways, we classified each study according to exposure pathway. We examined the availability of each study in PubMed, and if this was not the case, we tested its availability in Global Health.

Results
We extracted 2324 primary studies, of which 1936 were relevant to a specific climate-health exposure pathway. The range of primary studies available for our analysis per pathway was 73 to 439. For three pathways (air quality, heat stress, water quality & quantity) PubMed coverage was very high, at 91-94%. For another three pathways PubMed coverage was between 81-82% (extreme weather events, food supply & safety, vector distribution & ecology). Only the social factors pathway had an exceptionally low PubMed coverage of 40%. Half of the studies not available in PubMed were indexed in the Global Health database.

Conclusions
PubMed coverage of climate-health primary studies is mostly comprehensive, with a marked variability between three pathway clusters. Global Health can be recommended as secondary database. For some pathways additional sources are needed to identify all relevant studies.