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Eine Kritik deckt Mängel in der Sterblichkeitsstudie auf

von NFI Redaktion

A critique of a previously published article on Daylight Saving Time (DST) and European mortality from 1998–2012 discussed researchers‘ concerns regarding the key findings and interpretations of the study. The critique, published in Nature Communications, highlights significant flaws in the statistical analysis and conclusions of the study.

In the summary of the original article, the researchers reported a decrease in mortality in the two weeks following the spring transition with a reverse effect after the fall transition using a multiple negative binomial regression model. However, Figure 1 of the article showed the opposite effect – a slight increase compared to an already declining trend in mortality in spring and a slight decrease compared to an already rising trend in fall in the weeks following the transition to DST. These data are consistent with previous research on this topic.

The authors of the critique cited the following reasons for this discrepancy.

Daylight saving time debate: A critique unveils flaws in mortality study. Image source: Iryna Imago / ShutterstockDaylight saving time debate: A critique unveils flaws in mortality study. Image source: Iryna Imago / Shutterstock

Model Collinearity

Collinearity in nonlinear models is analogous to collinearity in linear models, indicating that certain variables are dependent on each other, but this lack of independence is not accounted for in the model.

In this case, the interdependent parameters are weeks following the transition to DST, month, season, temperature, humidity, and photoperiod. The collinearity is not explicitly tested in the analysis to determine the need for potential model adjustments.

Additionally, the model used does not test whether mortality-related parameters influence mortality rates in relation to transitions to DST. The authors of the critique suggest, for example, examining whether results are only observable for a specific year and whether gender or age composition differs before and after a transition.

Time Series and Seasonal Considerations

The dataset used in the study encompassed the entire time series, while the critique suggests limiting it to the data weeks immediately before and after the transitions. This restricted dataset would require fewer covariates and also reduce bias due to seasonal fluctuations in humidity, month, temperature, and photoperiod, which may have longer-term trends.

At the same time, the analysis presents comparisons of mortality rates based on a week before the transition to DST, without taking into account longer-term seasonal mortality trends showing an increase in fall and a decrease in spring. The authors of the critique suggest explicitly incorporating seasonal trends by using a design such as interrupted time series with a carefully defined pre- and post-interval period.

Differences at the Country Level

The dataset includes data from 16 countries, but the paper does not describe how the pooled regression model accounts for potential differences at the country level. Interactions between countries and other variables of interest are also not explicitly tested, which could lead to incorrect estimate variances and biased estimators.

The critique also points out that the statistical significance of the study results could be attributed to the large sample size, with the relative impact of DST transitions in the model being relatively small. The analysis also does not list causes of death, therefore not distinguishing between deaths from cancer (not attributable to DST) and traffic accidents (which are possible). Thus, there is limited evidence to support the claim in the original paper’s title that DST affects mortality.

Conclusions

The overall findings of the original article do not align with those of many previous studies. The transition to DST is associated with an increase in strokes and heart attacks. Furthermore, misalignment of the circadian rhythm and sleep disturbances due to increased inflammation, stress, and altered metabolism may have long-term health effects. DST also impairs neuropsychological function, which may be associated with an increase in traffic accidents and suicides.

The authors of the critique believe that policymakers need to consider these negative impacts and compare them with the short-term benefits of DST, such as increased light exposure during evening commutes from work. Numerous evidence suggests that permanently retaining standard time is the best option, as advocated by many doctors and researchers worldwide.

Journal Reference:

  • Daylight saving time and mortality – proceed with caution. Klerman, EB, Weaver, MD, Roenneberg, T., Malow, BA, Johnson, KG Nature Communications (2024). DOI: 10.1038/s41467-024-45837-4, Read More

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