Occupation and educational inequalities in laryngeal cancer: the use of a job index

Abstract

Background: Previous studies tried to assess the association between socioeconomic status and laryngeal cancer. Alcohol and tobacco consumption explain already a large part of the social inequalities. Occupational exposures might explain a part of the remaining but the components and pathways of the socioeconomic contribution have yet to be fully disentangled. The aim of this study was to evaluate the role of occupation using different occupational indices, differentiating between physical, psycho-social and toxic exposures and trying to summarize the occupational burden into one variable.

Methods: A population-based case-control study conducted in Germany in 1998-2000 included 208 male cases and 702 controls. Information on occupational history, smoking, alcohol consumption and education was collected with face-to-face interviews. A recently developed job-classification index was used to account for the occupational burden. A sub-index focussed on jobs involving potentially carcinogenic agents (CAI) for the upper aero digestive tract.

Results: When adjusted for smoking and alcohol consumption, higher odds ratios (ORs) were found for lower education. This OR decreased after further adjustment using the physical and psycho-social job indices (OR = 3.2, 95%-CI: 1.5-6.8), similar to the OR using the sub-index CAI (OR = 3.0, 95%-CI: 1.4-6.5).

Conclusions: The use of an easily applicable control variable, simply constructed on standard occupational job classifications, provides the possibility to differentiate between educational and occupational contributions. Such an index might indirectly reflect the effect of carcinogenic agents, which are not collected in many studies.

Figure 1

Distribution of worked years by cases and controls with less than 10 years of school. Percentages are calculated on the total years worked by cases and controls (8440.5 and 28894 respectively).

Figure 2

Distribution of (a) Overall Job Index (OJI), (b) Physical Job Index (PJI), (c) Psycho-Social Job Index (PSI), (d) Carcinogenic Agent Index (CAI) in cases and controls.

Figure 3

Lifetime Hours of Exposure (in 1.000) per person to reported Substances (SCL) in High (index value 9–10) (a) and Upper-middle (index value 6–8) (b) categories of the Carcinogenic Agent Index (CAI).