The association between zero-crossing temperatures and accidents due to icy conditions

Aims: Rising temperatures lead to milder winters in Scandinavia. In certain regions, this could increase the number of winter days that fluctuate around 0 degrees C (zero crossings). It has been frequently suggested that there is a higher risk of icy conditions during such days, which may lead to a predisposition to falls and road traffic accidents. Here, we examine the association between number of days with zero crossings and the number of hospitalisations and outpatient visits due to falls related to ice or snow or transport accidents. Methods: We used Poisson regression to examine the association between the number of days with zero crossings and the incidence of inpatient and outpatient visits related to falls due to ice and snow and to transport accidents during 2001-2017 in the Swedish cities of Stockholm, Malmo and Umea. Results: We found a positive and significant association between the number of days of zero crossings and the number of in- and outpatient cases due to falls related to ice and snow. These associations were strongest in Umea but less obvious in Stockholm and Malmo. In terms of injuries related to transport accidents, we saw a significant association between inpatient cases and number of zero crossings in Stockholm but not in Malmo or Umea. Conclusions: An increased number of zero crossings may increase out- and inpatient visits related to falls due to ice and snow or transport accidents. This effect is more pronounced in the northern city of Umea than in Malmo, a city in Sweden's southern-most region.