Comparison of distributions of morningness–eveningness among populations of shift workers on varied work patterns in different organizations

Abstract

We studied morningness–eveningness distribution in a cohort of 481 shift workers (SWs), from different organizations with varied shift-work patterns, namely 86 on running rotation (RR), 175 on weekly rotation, 173 on quick rotation (QR), and 47 on split rotation (SR). The prevalence of chronotype and distribution of morningness–eveningness score were studied. The preponderance of morning type was notable in the studied population of SWs, sampled from all four groups, except SR. Nevertheless, the frequency of early type was still higher in the SR group. Multiple linear regression models were fitted to find out relationship between the dependent variable, i.e., the log-transformed Morningness–Eveningness Questionnaire (MEQ) score, and a number of independent predictors (age, weight, height, body surface area, body mass index, and length of service) in all four clusters independently. Of the number of predictors, only the coefficient of “age” was statistically significant in RR and QR groups. In the present investigation, a notable departure of the distribution from the accepted Gaussian distribution of chronotype was witnessed. This could be ascribed to cultural differences between human populations of temperate and tropical regions. However, in the present study, a possible link between cultural differences and chronotype distribution has not been investigated.