Fig 1. Algorithm for evaluating overall strength of evidence for each combination of SEP exposure and outcome, based on quality, quantity, and consistency of the evidence [54].

High-quality studies were those that had controlled for age and sex in a multivariable analysis and had an NOS score of ≥7. Medium quality was assigned to studies that had controlled for age and/or sex in a multivariable analysis and had an NOS score of ≥5, or had not carried out multivariable analysis but had an NOS score of ≥6. Low-quality studies had no multivariable analysis and an NOS score of ≤5, or an NOS score of ≤4. High-strength evidence required ≥70% agreement about the direction of the exposure outcome association; moderate strength evidence required ≥60% agreement. NOS, Newcastle-Ottawa Quality Assessment Scale; SEP, socioeconomic position.