• Socioeconomic position
• occupational class
• comparability
• Cadmium

I have always found it difficult to consider the occupational class as an indicator of socioeconomic position (SEP) as presented by past researchers. Epidemiological findings are regulated by the concept or definition of variables, and application of the outcome should be considered in the situation of each social system. Although past researchers have quoted references on their occupational class and claimed to have proof of the validity of SEP, I feel that efforts to make their classification simpler are also required to improve the comparability of research outcomes.

Ferrario et al investigated the effect of occupational class on …