Table 2.

Study quality assessment

Study	Study participation	Study attrition	Risk factor measurement	Outcome measurement	Confounding Measurement	Statistical analysis and reporting
Dieck et al. [37]	High	High	High	Moderate	High	High
Grimby-Ekman et al. [36]	Moderate	High	Moderate	Low	Moderate	Low
Gustafsson et al. [35]	High	High	Moderate	Moderate	High	Low
Kanchanomai et al. [34]	High	High	Low	Low	High	Moderate
Siivola et al. [39]	Low	High	Moderate	Low	Moderate	Low
Timpka et al. [38]	Low	High	High	High	Moderate	Low

Study Participation: Representativeness of the study sample; Study Attrition: Data from participants not lost to follow-up accurately represent the persons enrolled in the study;Risk factor measurement: The risk factor is measured in a similar, valid and reliable way for all participants; Outcome measurement: The outcome is measures in a similar, valid and reliable way for all participants; Confounding measurement: Important potential confounding factors are addressed; Analysis: The analysis is appropriate, and all primary outcomes are reported