A recent study reported significantly increased mortality from drowning-related out-of-hospital cardiac arrest in Danish harbours compared to other public places (e.g., public pools, coastlines, and lakes). Accurate and reliable data are necessary before establishing specific educational, preventative, rescue, or treatment strategies to reduce the number of drowning incidents in Danish harbours and improve survival. Therefore, it is essential to characterise drowning incidents in Danish harbours and analyse risk factors associated with fatal drowning.

Based on the GPS coordinates and advanced text-searching, it is possible to identify drowning incidents in Danish harbours and extract data from the Danish Prehospital Drowning Data.

This study is a nationwide registry-based study with data from the Danish Prehospital Drowning Data from 2016 to 2023. In this study, we will use 30-day mortality to differentiate between fatal and non-fatal drowning.

The primary objective is to estimate the yearly incidence of fatal and non-fatal drowning incidents in Danish harbours treated by the EMS from 2016 to 2023 and calculate the fatal to non-fatal ratio. The secondary objective is to assess risk factors associated with 30-day mortality.

Inclusion Criteria:

• All the patients registered in the Danish Prehospital Drowning Data from 2016-2023 will be assessed for inclusion AND
• Incidents registered at GPS coordinates corresponding to a Danish harbour OR
• Incidents identified using advanced text-search algorithm searching for "harbour"-related words

Exclusion Criteria:

• Patients without a 30-day follow-up (e.g., due to missing or invalid civil registration numbers) and patients with a valid DNAR code will be excluded from the mortality analysis.

The target condition in this study is drowning, irrespective of follow-up at 30 days (fatal or non-fatal). We used the WHO definition of drowning supported by the clarification statement for non-fatal drowning as the case definition to identify drowning (target condition) during the manual validation.

The study unit is the individual drowning patient. The target population are all fatal and non-fatal drowning patients in Danish harbours treated by the EMS in Denmark since 2016. Due to the comprehensive search criteria in the Danish Drowning Formula, it is reasonable to believe that the target population is identical to the study population.

The datasets used and analysed during the current study are available from the corresponding author upon reasonable request.