Table 2

Risk of bias within cohort studies
Source Selection bias Information bias Confounding Appropriate sample size Appropriate analytic strategies
Emtner M et al. 1998 Low risk Low risk Low risk Unclear risk Appropriate
Emtner M et al. 1996 Low risk Low risk Low risk Unclear risk Appropriate
Engstom I, et al. 1991 Unclear risk Low risk Low risk Unclear risk Appropriate
Juvonen R, et al. 2008 Low risk Low risk Low risk Unclear risk Appropriate
Newcomb, P. et al. 2012 Unclear risk Low risk Low risk Unclear risk Appropriate
Nickerson BG et al., 1983 Low risk Low risk Low risk Unclear risk Appropriate
Silva PL, et al. 2011 Low risk Low risk Low risk Low risk Appropriate

Pakhale et al.

Pakhale et al. BMC Pulmonary Medicine 2013 13:38   doi:10.1186/1471-2466-13-38

Open Data