Table 3 The Newcastle–Ottawa Scale (NOS)

Author

Selection

Comparability

Outcome

Score

Representativeness of the exposed cohort

Selection of nonexposed cohort

Ascertainment of exposure

Demonstration that the outcome of interest was not present at the start of the study

Comparability of cohorts on the basis of the design or analysis

Assessment of outcomes

Follow-up was long enough for outcomes to occur

Adequacy of follow-up