title: Occupational cohort studies: the influence of design characteristics on the healthy worker effect.
abstract: A cross-sectional analysis of the relation between the estimated healthy worker effect (HWE), as measured by a total Standardized Mortality Ratio (SMR) less than 100, and relevant design characteristics in 270 published retrospective occupational cohort studies is presented. The majority of the reviewed studies showed a HWE, varying in SMR from 50 to 99 (mean: 84). The estimated HWE seemed to influence the final outcomes of the studies to a great extent. A tendency for a positive relation between the study size in terms of the number of exposed workers, total number of person-years of follow-up, and the HWE emerged. Studies with a comparatively short follow-up period had an increased chance of resulting in a HWE. Cross-sectional cohorts did not show a stronger HWE than open cohorts. Studies of chemical exposures revealed a fivefold excess of having a HWE compared with other studies.
authors.affiliation: Department of Occupational and Environmental Health and Toxicology, University of Limburg, Maastricht, The Netherlands.
authors.forename: J M
authors.initials: JM
authors.lastname: Meijers
authors.forename: G M
authors.initials: GM
authors.lastname: Swaen
authors.forename: A
authors.initials: A
authors.lastname: Volovics
authors.forename: L J
authors.initials: LJ
authors.lastname: Lucas
authors.forename: K
authors.initials: K
authors.lastname: van Vliet
mesh_terms: D015331:Cohort Studies; D003430:Cross-Sectional Studies; D015989:Healthy Worker Effect; D006801:Humans; D016015:Logistic Models; D009784:Occupational Diseases / Q000401:mortality*; D012016:Reference Values; D012107:Research Design / Q000592:standards*; D012189:Retrospective Studies