Analyzing the impacts of global trade and investment on non-communicable diseases and risk factors: a critical review of methodological approaches used in quantitative analyses

BACKGROUND: A key mechanism through which globalization has impacted health is the liberalization of trade and investment, yet relatively few studies to date have used quantitative methods to investigate the impacts of global trade and investment policies on non-communicable diseases and risk factors. Recent reviews of this literature have found heterogeneity in results and a range of quality across studies, which may be in part attributable to a lack of conceptual clarity and methodological inconsistencies. METHODS: This study is a critical review of methodological approaches used in the quantitative literature on global trade and investment and diet, tobacco, alcohol, and related health outcomes, with the objective of developing recommendations and providing resources to guide future robust, policy relevant research. A review of reviews, expert review, and reference tracing were employed to identify relevant studies, which were evaluated using a novel quality assessment tool designed for this research. RESULTS: Eight review articles and 34 quantitative studies were identified for inclusion. Important ways to improve this literature were identified and discussed: clearly defining exposures of interest and not conflating trade and investment; exploring mechanisms of broader relationships; increasing the use of individual-level data; ensuring consensus and consistency in key confounding variables; utilizing more sector-specific versus economy-wide trade and investment indicators; testing and adequately adjusting for autocorrelation and endogeneity when using longitudinal data; and presenting results from alternative statistical models and sensitivity analyses. To guide the development of future analyses, recommendations for international data sources for selected trade and investment indicators, as well as key gaps in the literature, are presented. CONCLUSION: More methodologically rigorous and consistent approaches in future quantitative studies on the impacts of global trade and investment policies on non-communicable diseases and risk factors can help to resolve inconsistencies of existing research and generate useful information to guide policy decisions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12992-018-0371-8) contains supplementary material, which is available to authorized users.