Avalanches: percentage of survivors up by ten percent since 1994

The survival rate of avalanche accidents has risen by ten percent over the past forty years. However, a new study using Swiss data reveals that the critical window for the highest survival probability has shrunk from 18 to just 10 minutes, likely due to changes in snow density. This emphasizes the crucial role of rescue by companions.

Modern avalanche transceivers, shovels and probes are now standard in ski touring. Along with a rise in the uptake of avalanche courses and increasingly efficient rescue teams, quicker detection and rescue of buried victims has also improved. The result: increased survival rates in avalanche burials over the past four decades. "Up until 1990, 43.5 percent of buried victims survived; now, it's 53.5 percent," explains Simon Rauch, the study's lead author and an emergency physician at Eurac Research. "We analyzed data from 1981 to 2020 and compared it with a 1994 Nature study that covered a ten-year period." The new analysis also shows that the survival probability for long-term burials (over 130 minutes) has increased from 2.6 percent to 7.3 percent. The average rescue time has dropped from 45 minutes to 25 minutes. Rescue time decreased from 15 to 10 minutes in cases when a companion was present, while organized rescue times fell from 153 to 90 minutes. However, the phase where survival probability exceeds 90 percent has shortened from 18 to just 10 minutes. "In 1994, we divided the survival curve into different phases and discovered that the first phase, when survival rate is very high, lasted up to 18 minutes. This became a global reference point in mountain rescue, but it now needs to be modified," says Hermann Brugger of Eurac Research, author of the original 1994 study and co-author of the current one. There are only hypotheses for the drastic reduction in this time window. "It could be that due to climate change and other factors, snow density has increased. The denser the snow, the less air it contains, making it harder to breathe under the snow." Rauch suggests. However, this theory has yet to be confirmed by data. "Time is the critical factor, and ten minutes is not long. Therefore, it's essential to understand that the survival chances in an avalanche burial are three times higher when excursion companions are able to dig out the victims, rather than when organized rescue teams are involved." Rauch emphasizes.

The study also highlights preventive measures such as avalanche warning services, training for ski tourers, and advancements in location and rescue techniques, along with improved emergency medical care, have significantly reduced the mortality rate for avalanche victims in recent decades. WSL, the Swiss Institute for Snow and Avalanche Research provided the data for the study, with biostatistician Markus Falk contributing a statistical analysis using a complex model.