Table 3.

Results of quality assessment for cohort studies.

First author, year	Selection				Comparability	Outcome
	Representativeness of exposed	Selection of nonexposed	Ascertainment of exposure	Outcome not present at start	Based on the study design or analysis	Ascertainment of outcome	Length of follow-up	Adequacy of follow-up
de Rooij, 2007	+	+	+		+	+	+	+
Yu, 2018	+	+	+		++	+	+	+