Job strain and risk of breast cancer.
BACKGROUND
Cohort studies investigating the association between stress and breast cancer have shown highly inconsistent results.


METHODS
The Women's Lifestyle and Health Cohort Study included 36,332 Swedish women age 30-50 years who were employed at baseline (1991-1992). Participants were followed through December 2004 using linkages to national registries. A total of 767 women were diagnosed with breast cancer during follow-up.


RESULTS
Among women working full-time, low job control and high job demands were weakly associated with breast cancer risk (hazard ratios of 1.2; 95% CI = 1.0-1.5). Women with both low job control and high job demands ("job strain") had higher risk of breast cancer than women with high job control and low demands ("low strain") (1.2; 0.9-1.6). Multivariate adjustment slightly strengthened the association between breast cancer and job strain (1.4; 1.1-1.9), whereas the associations with control and demands were unchanged. Work characteristics were unrelated to breast cancer risk among women working part-time.


CONCLUSIONS
There was a small increased risk of breast cancer among women in full-time employment who experienced job strain, but not among part-time workers.
Kuper
Hannah
H
Clinical Research Unit, London School of Hygiene and Tropical Medicine, London, UK. hannah.kuper@lshtm.ac.uk
Yang
Ling
L
Theorell
Tores
T
Weiderpass
Elisabete
E
D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D016273:Occupational Exposure; D018570:Risk Assessment; D013315:Stress, Psychological; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology