The riddle of shiftwork and disturbed chronobiology: A case study of landmark smoking data demonstrates fallacies of not considering the ubiquity of an exposure

Abstract

Background: Failing to integrate all sources of a ubiquitous hazard candidate may explain inconsistent and/or null, and overall misleading, results in epidemiological studies such as those related to shift-work. Methods: We explore this rationale on the assumption that Doll and Hill had confined their 1950 landmark study to smoking at workplaces alone. We assess how non-differential, or how differential, underestimation of exposure could have biased computed risks. Results: Systematically unappreciated exposures at play could have led to substantial information bias. Beyond affecting the magnitude of risks, not even the direction of risk distortion would have been predictable. Conclusions: Disturbed chronobiology research should consider cumulative doses from all walks of life. This is a conditio sine qua non to avoid potentially biased and uninterpretable risk estimates when assessing effects of a ubiquitous hazard candidate.