Table 2.

Study quality of included studies based on the Newcastle-Ottawa scale.

Author	Represent activeness of the exposed cohort	Selection of the non-exposed cohort	Ascertainment of exposure	Demonstration that outcome of interest was not present at start of study	Comparability of cohorts on the basis of the design or analysis	Ascertainment of outcome	Was follow-up long enough for outcomes to occur	Adequacy of follow up of cohort	Total scores
Iribarren, 2004	★	★	★	★	★★	★	★	★	9
Marco, 2005	★	★	★	⋆	★⋆	★	★	★	7
Schanen, 2005	★	★	★	⋆	★★	★	★	★	8
Bellia, 2007	★	★	★	⋆	★⋆	★	★	★	7
Onufrak, 2008	★	★	★	⋆	★★	★	★	⋆	7
Hyun, 2012	★	★	★	★	★⋆	★	★	★	8
Chung(ACS), 2014	★	★	★	★	★★	★	★	⋆	8
Chung(Stroke)m 2014	★	★	★	★	★★	★	★	⋆	8
Matthew, 2015	★	★	★	⋆	★★	★	★	★	8
Yunus, 2015	★	★	★	⋆	★★	★	★	★	8

See quality assessment in methods for explanation of ratings.