Job-exposure matrices addressing lifestyle factors

Correspondence to Dr Melissa C Friesen, Division of Cancer Epidemiology and Genetics, Occupational and Environmental Epidemiology, National Cancer Institute, Rockville MD 20850, USA; friesenmc@mail.nih.gov This issue of Occupational and Environmental Medicine includes the description of a novel job-exposure matrix (JEM) designed to characterise job-specific differences in lifestyle risk factors developed by Bondo Petersen et al,1 with the aim to provide lifestyle adjustment in aetiological analyses in Danish cancer registry-based studies. Only one similar set of lifestyle JEMs exist to my knowledge: in 2005, the Finish job-exposure matrix (FINJEM) added occupation and gender-specific JEM estimates for the time period 1995–1997 for similar lifestyle characteristics based on surveys on Finnish adult health behaviours conducted between 1993 and 1999.2 The Danish lifestyle JEMs are the first to provide estimates for multiple time periods, employing 5-year time windows over three decades. Additionally, the Danish survey data were systematically analysed using mixed-effects statistical models that incorporated occupation classification code as a random effect to provide job group-specific estimates and incorporated age, time period, gender and data source as fixed effects to account for age-specific, year-specific and gender-specific differences.