Table 4.

Demonstrates use of ROBINS-I tool for assessment of risk of bias in included studies

	Study	Confounding	Selection	Intervention classification	Deviation from intervention	Missing data	Measurement of outcome	Selection of reported result	Overall
1	Statham 1989	Low	Moderate	Low	Low	Moderate	Low	Low	Moderate
2	Peterson 2011	Moderate	Moderate	Low	Moderate	Moderate	Low	Low	Moderate
3	Gao 2013	Moderate	Moderate	Moderate	Low	Critical	Low	Critical	Critical
4	Dong 2012	Moderate	Serious	Low	Low	Low	Low	Low	Serious
5	Wu 2014	Critical	Serious	Low	Low	Low	Serious	Low	Critical
6	Sarma 2015	Critical	Low	Serious	Low	Moderate	Serious	Critical	Critical
7	Zhaofeng 2016	Critical	Moderate	Low	Low	Low	Low	Low	Critical