Alternative comparison populations to assess occupation-related mortality risk: Results for the high nickel alloys workers cohort 

The focus of this paper is to examine how the choice of comparison group affects the identification and interpretation of cause-specific health risks in occupational cohorts when using different external control populations. The mortality experience of approximately thirty-one thousand high nickel alloys workers is compared to the total United States population and to local populations in geographic proximity to the plants.

Generally, the patterns of relative risks derived for the total cohort and various subgroups are similar across the different comparison populations. Estimated elevated risks are usually lower when cohort mortality is compared to that of local populations. An overall significant 13% risk for lung cancer is noted when compared to the total United States population. However, no significant excess is identified when using local populations.

Subset analysis identified significant excesses of colon cancer among nonwhite males (50% - 150%) and kidney cancer among white male workers employed in melting (approximately 100%) irrespective of the comparison population.