In the GRADE approach, sound observational studies are usually given a quality rating of “low,” while a rating of “high” is given to randomized trials.7 However, due to the nature of built environment studies, randomized trials are rarely, if ever, used since it would be unethical and highly unfeasible to randomize community-level exposures in humans. So, sound observational studies are given a rating of “moderate” or are upgraded or downgraded, based on quality.
Two graders systematically evaluate each study using the GRADE approach. If the quality level does not match between the two graders for any study, a third grader can read the article and resolve the discrepancy. For each association, graders then determine the percentage of studies with results in the hypothesized direction that have “high,” “moderate,” “low,” and “very low” quality. Graders use Table 1 to rate the strength of evidence for each hypothesized association as “strong,” “sufficient,” or “insufficient.”
Impact Assessment Table
The impact assessment table visually displays the direction, strength, likelihood, severity, magnitude, and distribution of these potential health associations. These methods were based on
Health Impact Assessment: A Guide for Practice8 and
A Health Impact Assessment Toolkit: A Handbook to Conducting HIA, 3rd Edition.9
Impact Table Key
Direction:
Shows the impact direction of the development features and their outcomes:
Positive: The changes may improve health
Negative: The changes may impair health
Uncertain: It is unknown how health may be affected
No effect: There will be no health effect
Strength of Evidence:
Evaluated strength of evidence for each association using Table 1:
Strong: There is strong evidence for the association
Sufficient: There is sufficient evidence for the association
Insufficient: There is insufficient evidence for the association
Likelihood:
Answers the question, “How certain is it that the development features and outcomes will affect health outcomes, irrespective of the frequency, magnitude, or severity?”
Very likely: There is enough evidence for a causal, generalizable effect
Likely: The effect is logically plausible with substantial, consistent supporting evidence
Possible: The effect is logically plausible with limited supporting evidence
Unlikely: The effect is logically implausible, with substantial evidence against the mechanism of effect
Severity:
Answers the question, “How severe is the negative health consequence that results or is avoided after the proposed changes are implemented with regards to human well-being, function, or longevity, considering the community’s ability to manage the health effects?”
High: Health effects that are chronic, irreversible, or fatal
Medium: Health effects that necessitate treatment or medical management; effects are reversible
Low: Health effects that can be quickly and easily managed or that do not need treatment
Magnitude of Association:
Answers the question, “How large is the measure of association between the proposed change and the outcome of interest?” The levels of magnitude are considered to be “substantial,” “moderate,” or “limited” based on Table 2 below. If all of the results for an association do not agree on a specific level of magnitude, an average is taken. For example: If three articles find a “substantial” level of magnitude, while three articles find a “limited” level of magnitude, a level of “moderate” would be reported for that association. If there is an equal number of articles reporting a “limited” and “moderate” or a “moderate” and “substantial” magnitude, then the lower level is reported.
Distribution:
Answers the question, “Who will be affected by the proposed changes?”