Figure 2. Circadian Disruption in laboratory and field settings.

The left panel displays potential causes of disruption and how they might differ between laboratory and field settings. On the upper part of the right panel, sample variability of the study population is illustrated. While laboratory studies usually target specific populations in a smaller number of individuals, field studies include larger and more heterogeneous samples. Both approaches are valid. Laboratory studies minimize noise in the signal by selecting homogenous samples, and thereby can detect even small effects. However, generalizability is limited. The resulting levels of disruption (lower right panel) should this differ between laboratory and field settings, with high contrast conditions and little inter-individual variability in laboratory settings, and higher variability in field ones. In view of our improved understanding of circadian organization, including the relevance of peripheral clocks, future work is needed to harmonize conceptual approaches and operationalization of circadian disruption in the context of mechanistic, observational and intervention studies. Figure credit: Olivia Walch, PhD, twitter: @oliviawalch).