Academic journal article Environmental Health Perspectives

The Navigation Guide Systematic Review Methodology: A Rigorous and Transparent Method for Translating Environmental Health Science into Better Health Outcomes

Academic journal article Environmental Health Perspectives

The Navigation Guide Systematic Review Methodology: A Rigorous and Transparent Method for Translating Environmental Health Science into Better Health Outcomes

Article excerpt

Introduction

There is an urgent unmet need to shorten the time between scientific discovery and improved health outcomes. Population exposure to toxic environmental chemicals is ubiquitous [Centers for Disease Control and Prevention (CDC) 2014; U.S. Environmental Protection Agency (EPA) 2013c], and adverse health outcomes associated with exposure to such chemicals are prevalent and on the rise (Newbold and Heindel 2010; Olden et al. 2011; U.S. EPA 2013c; Woodruff et al. 2010; World Health Organization and United Nations Environment Programme 2013). The health and economic benefits of translating scientific discoveries into actions to prevent harm and reap benefits have been clearly demonstrated. For example, global efforts to remove lead from gasoline have produced health and social benefits estimated at $2.4 trillion dollars annually (Tsai and Hatfield 2011); and the value of better air quality, including reductions in premature death and illness, and improved economic welfare and environmental conditions from the programs implemented pursuant to the Clean Air Act Amendments of 1990, will reach almost $2 trillion dollars in 2020 (U.S. EPA 2011). However, many potential benefits have been squandered due to delays in acting on the available science (European Environment Agency 2013). Because of deficiencies in the current regulatory structure for manufactured chemicals, a failure or delay in acting on the science means that exposure to toxic chemicals persists while evidence of harm mounts (Vogel and Roberts 2011).

Failing or delaying to take action to prevent exposure to harmful environmental chemicals is not an inconsequential or neutral policy choice. For example, the costs in 2008 to the U.S. health care system for treatment of childhood illnesses linked to toxic environmental exposures has been estimated to be > $76 billion (Trasande and Liu 2011). Failure to prevent even low-level environmental exposures can have large society-wide adverse consequences for health if exposures are ubiquitous (Bellinger 2012).

To the extent that science informs public policy to prevent harm, a robust method to synthesize what is known about the environmental drivers of health in a transparent and systematic manner is a necessary foundational step to making the science actionable. The body of science is voluminous, of variable quality, and largely unfamiliar to decision makers. Early warning signals of harm can be masked by the fragmented, complex, and at times, conflicting nature of the available information, undermining our capacity to act wisely. Yet, consistently applied and transparent rules and descriptors about how environmental health science is translated into strength of evidence conclusions have been lacking [Beronius et al. 2010; Gee 2008; National Research Council (NRC) 2009, 2011].

Today, methods of research synthesis prevalent in environmental health mirror that of clinical medicine > 40 years ago when the clinical sciences largely relied on a system of expert-based narrative reviews on which to recommend treatment decisions (Rennie and Chalmers 2009). In a landmark paper published in 1992 in the Journal of the American Medical Association, Antman et al. (1992) showed the superiority of systematic review methods by comparing expert opinion-based recommendations for treatment of myocardial infarction published in scientific reviews and clinical textbooks to statistical analyses of the combined results of randomized controlled trials. Antman et al. documented the lack of timely incorporation of experimental evidence into expert-based recommendations and showed that some expert reviews did not mention effective therapies, whereas others recommended therapies proven to be ineffective or even dangerous. From there, explicit approaches that harness expertise to a rigorous, transparent, and systematic methodology to evaluate a clearly formulated question were advanced, and are now embodied in prominent empirically demonstrated methods such as the Cochrane Collaboration (Higgins and Green 2011) and Grading of Recommendations Assessment, Development and Evaluation (GRADE) (Guyatt et al. …

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