Evidence mapping: methodologic foundations and application to intervention and observational research on sugar-sweetened beverages and health outcomes.

BACKGROUND: Evidence maps are a new method that systematically characterize the range of research activity in broad topic areas and are used to guide research priority setting, systematic reviews, and meta-analyses.
OBJECTIVE: We expanded evidence mapping methods by demonstrating their usefulness as a tool for organizing epidemiologic research on sugar-sweetened beverage (SSB) intake and health outcomes: obesity, type 2 diabetes, metabolic syndrome, and coronary heart disease/stroke.
DESIGN: We performed a search of the PubMed, Scopus, and Cochrane databases and a hand search of references. Studies selected were reviews and longitudinal studies (intervention and cohort) published between 1 January 1966 and 31 October 2012.
RESULTS: We identified and mapped 77 studies (18 review and 59 primary research articles); most of the research focused on obesity (n = 47). For all outcomes, >30% (n = 18) of the primary research studies we identified were not referenced in published reviews. We found considerable variability among primary research studies of SSBs and the 4 health outcomes in terms of designs, definitions of SSBs, and definitions of outcomes, which renders these studies difficult to interpret collectively. For example, we counted 14 different definitions of weight/obesity in 29 observational cohort studies, and ≤6 studies reported the use of the same outcome measure.
CONCLUSIONS: Establishing field standards in the study of SSB intake and health outcomes would facilitate interpretation across research studies and thereby increase the utility of systematic reviews/meta-analyses and ultimately the efficiency of research efforts. Rapid publication of new data suggests the need for regular updates and caution when reading reviews.