Is there a healthy worker effect for cancer incidence among women in Sweden?

Our aim was to evaluate whether there is a healthy worker effect (HWE) for cancer incidence among women. HWE is a bias found in occupational studies that compare rates of disease among employed people to disease rates for the general population, which includes unemployed people (who may be less healthy than those who are employed).

Data from the 1960 and 1970 Swedish censuses were used to identify all 1,659,940 Swedish women who were employed in either year. They were followed during 1971-1989 through linkages to the national cancer and death registers. Standardized incidence ratios (SIRs) were computed comparing employed women to the 1,627,873 women who were not employed in either 1960 or 1970.

For the 545,857 women employed in both 1960 and 1970, the SIR for all cancers combined was 1.05 (1.04-1.06). When specific cancer sites were analyzed separately, the highest cancer risks were for cancers of the lung and bladder (SIR = 1.2) and reproductive organs (breast, ovary, endometrium, and cervix SIR = 1.1). Overall cancer risks were highest among full-time workers, younger workers, urban workers, and workers with the highest socioeconomic status (based on the woman's job title).

These results show no general HWE for cancer incidence among employed Swedish women.