Prevalence of sleep disturbance in Chinese healthcare professionals increases Eastward: caution with position in time zones

This is the Authors’ accepted version published in zenodo doi:10.5281/zenodo.14140768 The Version of Record ©Elsevier BV is available in Sleep Medicine under doi:10.1016/j.sleep.2024.11.021 Prevalence of sleep disturbance in Chinese healthcare professionals increases Eastward: caution with position in time zone Jos´e Mar´ıa Mart´ın-Olalla Universidad de Sevilla, Facultad de F´ısica, Departamento de F´ısica de la Materia Condensada, ES41012 Sevilla, Spain∗ Jorge Mira Universidade de Santiago de Compostela, Facultade de F´ısica, Departamento de F´ısica Aplicada and iMATUS, ES15782 Santiago de Compostela, Spain† (Dated: 13 November 2024) We analyze data of the prevalence of sleep disturbance among Chinese healthcare professionals and maintain that they increase Eastward, refining previous results. We suggest that position in time zone is a valid explanatory metric only after daily rhythms have been uniformed. On a more general note, this finding suggest that daylight saving time might help reduce sleep disturbance. •Sleep disturbance among Chinese healthcare professionals monotonically increases Eastward. •Position in time zone is an explanatory variable only if uniform daily rhythms are analyzed. •Daylight saving time might help to reduce sleep disturbance. File: main.tex Encoding: utf8 Words in text: 649 Words in headers: 15 Words outside text (captions, etc.): 100 Number of headers: 4 Number of floats/tables/figures: 1 Number of math inlines: 7 Number of math displayed: 0 Subcounts: text+headers+captions (#headers/#floats/#inlines/#displayed) 508+11+100 (2/1/7/0) _top_ 29+1+0 (1/0/0/0) Section: Acknowledgments 112+3+0 (1/0/0/0) Section: Manuscript time line Keywords: DST; sleep deprivation; position in time zone; time zone offset; daylight saving time; daily rhythms Borisenkov [1] took data by Qiu et al.[2] on the prevalence of sleep disturbance among Chinese healthcare professionals and contrasted them with the position in time zone (PTZ, longitude offset relative to the Beijing meridian, 115◦E) to report that “when moving away from the Beijing meridian by 10◦to the left or right, there is an in- ∗[email protected]; https://orcid.org/0000-0002-3750-9113; https://ror.org/03yxnpp24 †[email protected]; https://orcid.org/0000-0002-6024-6294; https://ror.org/030eybx10 crease in the frequency of detection of sleep disturbances by 6.5 %”. Later, Johnson and Malow [3] used this result as one evidence of the chronic hazards associated with daylight saving time (DST), a shift to the left (Westward) of the time zone. However, we want to highlight that results from Ref. [1] actually show an increase of the prevalence when moving away to the right (Eastward) of the Beijing meridian, so that DST would reduce the hazards. Borisenkov [1] fits the prevalence of sleep disturbance to a cubic polynomial. His fitting solution is not monotonic: prevalence increases East and West of the BeiTypeset by REVT EX 2 jing meridian, where the prevalence is minimal (optimal). Yet, all meridians are equal; a prime meridian just signals a reference; no outcome can be associated with it. In other words, only a monotonic trend where the prevalence increases or decreases with PTZ would be meaningful. PTZ is a nice explanatory variable as long as the daily rhythms are similar in the dataset, like is the case in USA[4] and Russia[5], but not in the Central European Time zone —that extends ∼33◦degrees from Poland and North Macedonia (East) to Spain (West)—, where the presumed impact of PTZ is mitigated by a gradient of daily rhythms that shows early activity on the East side and late activity on the West side, following Earth’s rotation[6]. China —60◦wide East to West— likely shows the same pattern. We understand that life in the Xinjiang region is delayed relative to life in Beijing, following the delay in solar ephemerides. In Ref. [1, Figure 1B], this would move Xinjiang data 15◦to the East per one hour delay, which brings a slight increase of the prevalence in sleep disturbance Eastward, as shown in figure 1. ACKNOWLEDGMENTS This work was not funded. Figure 1B in Ref. [1] was digitized with WebPlotDigitizer 4.17 online version https://apps.automeris.io/wpd/. Code can be accessed in https://github.com/automeris-io/ WebPlotDigitizer/releases REFERENCES [1] M. F. Borisenkov, Latitudinal and longitudinal distribution of the prevalence of sleep disturbances among healthcare professionals in china: a chronobiological explanation, Sleep Medicine 77, 281 (2021). [2] D. Qiu, Y. Yu, R. Q. Li, Y. L. Li, and S. Y. Xiao, Prevalence of sleep disturbances in chinese healthcare professionals: a systematic review and meta-analysis, Sleep Medicine 67, 258 (2020). [3] K. G. Johnson and B. A. Malow, Daylight saving time: Neurological and neuropsychological implications, Current Sleep Medicine Reports 8, 86 (2022). [4] O. Giuntella and F. Mazzonna, Sunset time and the economic effects of social jetlag: evidence from us time zone borders, Journal of Health Economics 65, 210 (2019). [5] M. F. Borisenkov, Latitude of residence and position in time zone are predictors of cancer incidence, cancer mortality, and life expectancy at birth, Chronobiology International 28, 155 (2011). [6] J. M. Mart´ın-Olalla, Latitudinal trends in human primary activities: characterizing the winter day as a synchronizer, Scientific Reports 8, 5350 (2018). MANUSCRIPT TIME LINE On 25 March 2024, the authors were carefully reading Johnson and Malow [3] review paper on Daylight Saving Time when Table 1 caught their attention. They went on to test the references listed on that table and read thoroughly Borisenkov [1]’s analysis. A tweet https://x.com/MartinOlalla_JM/ status/1772216191957758178 was posted on the occasion. The response letter was written and submitted on the the spot. The first decision was received on 3 October 2024, 190 days after the initial submission —6 months and 6 days—. The revised version was submitted on 9 October 2024. It was accepted on 11 November 2024, one month later, and 230 days —seven months and sixteen days— from the initial submission and published on-line (Journal online proofs) on 13 November 2024. 3 0 % 20 % 40 % 60 % 80 % 100 % −30◦ −15◦0◦15◦ −2 h −1 h 0 h 1 h Prevalence of sleep disturbance Position in time zone (offset relative to the 115◦E meridian) Time offset relative to the 115◦E meridian Dataset (w/o Xinjiang) Xinjiang (original) Xinjiang plus 15◦ Xinjiang plus 30◦ Regression line 95 % PI Figure 1 The association of position in time zone vs the prevalence of the sleep disturbance in healthcare professionals in China. For the original data the association brings p= 0.79 and the null hypothesis “prevalence does not depend on position in time zone” sustains at the standard level of significance α= 0.05. If Xinjiang data are moved 15◦, or one hour phase delay, then p= 0.31. If Xinjiang data were moved 30◦, then p= 0.044; R2= 0.09 and the null hypothesis would not sustain. The slope would be 0.15 basis points of increase in the prevalence per 15◦of change to the East. The regression line and the 95 % prediction interval are shown.