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Table 2 Quality assessment of included studies

From: Physical activity is associated with reduced risk of esophageal cancer, particularly esophageal adenocarcinoma: a systematic review and meta-analysis

 

Bias in study design

Bias in instrument to measure physical activity

Bias in accounting for confounding variables

Overall quality of study

Cohort studies

Huerta [15]

Low

Low

Low

High

Leitzmann [16]

Low

Low

Low

High

Wannamethee [23]

Low

Low

Low

High

Yun [24]

Low

Low

Low

High

Case–control Studies

Balbuena [26]

High

High

High

Low

Brownson [25]

High

High

Low

Low

Etemadi [27]

High

High

High

Low

Parent [13]

Low

High

Low

Low

Vigen [14]

Low

High

Low

Low

  1. Briefly, we used a three-item checklist to identify whether studies were at low or high risk of bias, based on: (a) study design – low risk of bias if cohort or population-based case–control studies, and high risk of bias if hospital-based case–control or exclusively cancer registry-based; (b) instrument used to measure physical activity – low risk of bias if instrument valid and reliable as shown in index study or related study, and high risk of bias if not reported; (c) key variables adjusted or accounted for: if a study adjusted, matched or accounted for the potential confounding effect of age, sex and obesity in their analysis, then those studies were considered to be at low risk of bias, otherwise they were considered to be at high risk of bias. Overall, if a study was deemed to be at low-risk of bias across all these domains, then it was considered a high-quality study, otherwise it was considered a low-quality study.