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Table 6 Risk of bias table

From: Childhood body mass index and subsequent physician-diagnosed asthma: a systematic review and meta-analysis of prospective cohort studies

Bias Studies Authors’ judgment Support for judgment
Incomplete outcome data (attrition bias) Gilliland et al., 2003[45]; Gold et al., 2003[46]; Mannino et al., 2006[48] Unclear risk Number of participants lost to follow-up not reported
Mamun et al., 2007[47] High risk 46.5% of original cohort lost to follow-up by age 5 years; 59.6% of original cohort has incomplete data at either age 5 years or 14 years and was excluded from analysis
Zhang et al., 2010[49] Low risk 89.6% of original cohort sampled at 6 year visit; 82.4% of original cohort sampled at 8 year visit
Ho et al., 2011[50] Unclear risk 82% of selected original cohort with complete data at 12 month follow-up
Ascertainment bias Gilliland et al., 2003[45]; Gold et al., 2003[46]; Mamun et al., 2007[47]; Mannino et al., 2006[48]; Zhang et al., 2010[49]; Ho et al., 2011[50] Unclear risk Unclear if children who were overweight or obese were more likely to be diagnosed with asthma
Differential misclassification of exposure bias Mannino et al., 2006[48] High risk Only 69% of height and 61% of the weights were measured