What is the relationship between changes in the size of economies and mortality derived population health measures in high income countries: A causal systematic review

Context: The economy has been long recognised as an important determinant of population health and a healthy population is considered important for economic prosperity. Aim: To systematically review the evidence for a causal bidirectional relationship between aggregate economic activity (AEA) at national level for High Income Countries, and 1) population health (using mortality and life expectancy rates as indicators) and 2) inequalities in population health. Methods: We undertook a systematic review of quantitative studies considering the relationship between AEA (GDP, GNI, GNP or recession) and population health (mortality or life expectancy) and inequalities for High Income Countries. We searched eight databases and grey literature. Study quality was assessed using an adapted version of the Effective Public Health Practice Project's Quality Assessment tool. We used Gordis' adaptation of the Bradford-Hill framework to assess causality. The studies were synthesised using Cochrane recommended alternative methods to meta-analysis and reported following the Synthesis without Meta-analysis (SWiM) guidelines. We assessed the certainty of the evidence base in line with GRADE principles. Findings: Of 21,099 records screened, 51 articles were included in our analysis. There was no evidence for a consistent causal relationship (either beneficial or harmful) of changes in AEA leading to changes in population health (as indicated by mortality or life expectancy). There was evidence suggesting that better population health is causally related to greater AEA, but with low certainty. There was insufficient evidence to consider the causal impact of AEA on health inequalities or vice versa. Conclusions: Changes in AEA in High Income Countries did not have a consistently beneficial or harmful causal relationship with health, suggesting that impacts observed may be contextually contingent. We tentatively suggest that improving population health might be important for economic prosperity. Whether or not AEA and health inequalities are causally linked is yet to be established.