Table 1 Newcastle-Ottawa scale used for methodological quality assessment of non-RCT

1、

Assignment for treatment: any criteria reported? (if yes, 1 star)

2、

How representative was the reference group (CABG) in comparison with the general elderly population for CABG? (if yes,1 star; 0 star if the patients were selected or selection of group was not described)

3、

How representative was the treatment group (HCR) in comparison with the elderly population for CABG? (if drawn from the same community as the reference group, 1 star; 0 star if drawn from a different source or selection of group was not described)

Comparability

4、

Group comparable for 1, 2, 3, 4,5 (if yes, 2 stars; one star was assigned if one of these five characteristics was not reported even if there were no other differences between the two groups and other characteristics had been controlled for; 0 star was assigned if the two groups differed)

5、

Group comparable for 6, 7, 8,9,10 (if yes, 2 stars; one star was assigned if one of these four characteristics was not reported even if there were no other differences between the two groups and other characteristics had been controlled for; 0 star was assigned if the two groups differed)

Outcome assessment

6、

Clearly defined outcome of interest (yes, 1 star for information ascertained by record lincage or interview; 0 star if this information was not reported)

7、

Adequacy of follow-up (1 star if follow-up above 90%)