Table 2 Newcastle–Ottawa quality assessment scale for cohort studies.

Study

Selection

Design or analysis controlled for confounders

Outcome

Quality score

Representativeness of the case-cohort

Selection of the control cohort

Ascertainment of outcome

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

Assessment of the outcome

Follow-up was long enough for outcomes to occur

Adequacy of follow-up of cohorts