Table 1.

Newcastle‐Ottawa Quality Assessment Scale for Cohort Studies

	Pastori et al.( 5 )	Goriacko et al.( 10 )	Lee HF et al.( 11 )	Lee SR et al.( 12 )
Selection
Representativeness of the exposed cohort
A Truly representative of the average in the community*	A	B	B	A
B Somewhat representative of the average in the community*
C Selected group of users (e.g., nurses, volunteers)
D No description of the derivation of the cohort
Selection of the nonexposed cohort
A Drawn from the same community as the exposed cohort*	A	A	A	A
B Drawn from a different source
C No description of the derivation of the nonexposed cohort
Ascertainment of exposure
A Secure record (e.g., surgical records)*	A	A	A	A
B Structured interview*
C Written self‐report
D No description
Demonstration that outcome of interest was not present at start of study
A Yes*	A	A	A	A
B No
Comparability
Comparability of cohorts on the basis of the design or analysis
A Study controls for age and/or sex*, †	B	B	B	B
B Study controls for any additional factor*, †
Outcome
Assessment of outcome
A Independent blind assessment*	A	B	B	B
B Record linkage*
C Self‐report
D No description
Was follow‐up long enough for outcomes to occur?
A Yes (≥12 months)*	A	B	A	A
B No
Adequacy of follow‐up of cohorts
A Complete follow‐up (all subjects accounted for)*	D	D	D	D
B Subjects lost to follow‐up unlikely to introduce bias (small number lost) >80% in follow‐up or description provided of those lost*
C Follow‐up rate <80% and no description of those lost
D No statement
Total score †	8	7	8	8

^*Point assigned only to these criteria.

^†1 point if studies adjusted for age and/or sex; 2 points if studies adjusted for age and sex and/or any other cardiovascular risk factor.