Impact of winter holiday and government responses on mortality in Europe during the first wave of the COVID-19 pandemic

  1. Jonas Björk
  2. Kristoffer Mattisson
  3. Anders Ahlbom

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Abstract

Background

This aggregated population study investigated the impact of the seemingly quasi-randomly assigned school winter holiday in weeks 6–10 (February to early March) on excess mortality in 219 European regions (11 countries) during the COVID-19 pandemic in the spring 2020. A secondary aim was to evaluate the impact of government responses to the early inflow of infected cases.

Methods

Data on government responses weeks 8–14 were obtained from the Oxford COVID-19 Government Response Tracker. Regional data on total all-cause mortality during weeks 14–23 in 2020 were retrieved from Eurostat and national statistical agencies and compared with the average mortality during same period 2015–2019. Variance-weighted least square regression was used with mortality difference as dependent variable with adjustment for country, population density and age distribution.

Results

Being a region with winter holiday exclusively in week 9 was in the adjusted analysis associated with 16 weekly excess deaths [95% confidence interval (CI) 13–20] per million inhabitants during weeks 14–23, which corresponds to 38% of the excess mortality in these regions. A more stringent response implemented in week 11, corresponding to 10 additional units on the 0–100 ordinal scale, was associated with 20 fewer weekly deaths (95% CI 18–22) per million inhabitants.

Conclusions

Winter holiday in week 9 was an amplifying event that contributed importantly to the excess mortality observed in the study regions during the spring 2020. Timely government responses to the resulting early inflow of cases reduced the excess in mortality.

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  1. Version published to 10.1093/eurpub/ckab017
  2. ScreenIT

    SciScore for 10.1101/2020.11.24.20237644: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    (Stata Corp.) and IBM SPSS Statistics 25
    SPSS
    suggested: (SPSS, RRID:SCR_002865)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Our study had several limitations. The use of aggregated data means that results can be subject to ecological inference fallacy, i.e. that the observed associations are not necessarily reflecting true or correctly estimated associations on the individual level.16 The ecological analysis is generally sensitive to choice of adjustment factors. We decided to include adjustment for country, which effectively implies that associations between winter holiday week and excess mortality in each country are pooled together in the regression analysis. But it also means that only countries where the winter holiday week differed across regions contribute to the estimated exposure effect. Another limitation was that the calculation of the expected mortality in a region was only adjusted for changes in population size, and did not take time trends, yearly fluctuations (e.g. mean temperature a given year or severity of the flu season) or other population changes into account.13 A further limitation was that we that we only estimated the effect of the winter holiday for each region separately and did not consider spill-over effects to neighbouring regions from for example commuting or regional travelling. In this respect, it is therefore likely that our estimates represent the lower bound of the winter holiday effect. It should also be noted that government response was only evaluated in the initial phase of the pandemic. Lockdown measures and other restrictions that last for longer time peri...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

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  3. Version published to 10.1101/2020.11.24.20237644 on medRxiv