Occupation and risk of non-Hodgkin's lymphoma in Singapore

Aims To examine the possible association between occupation and risk of NHL in the Singapore population. Methods A hospital-based interviewer-administered case-control study was carried out in five major hospitals in Singapore between April 2004 and December 2008. A complete occupational history, which included all jobs lasting over 1 year since graduation from school, was obtained for each participant. The Singapore Standard Occupational Classification was used for coding all occupations recorded. Results Eight hundred and thirty controls and 465 NHL cases, comprising B-cell (n = 404, 87%) as well as T- and NK-cell (n = 61, 13%) neoplasms, were recruited. Having ever worked as a teacher was associated with a significantly higher risk of NHL (adjusted OR 2.04, 95% CI 1.12-3.72). Teachers who had taught for < 10 years had a significantly higher risk of NHL (adjusted OR 2.44, 95% CI 1.11-5.34), but we did not observe an elevated risk for those who reported teaching for > 10 years. Among the 31 teachers with NHL, 23% taught in upper secondary schools, with equal proportions (13%) teaching in primary and pre-primary schools, respectively. The remainder taught in other settings. Conclusions Teachers come into frequent contact with children and may consequently have higher rates of exposure to common infectious agents. Therefore, the hypothesis of an infective aetiology of NHL may be supported by our findings.