Drowning in Denmark: A Six-year Registry-based Study of Fatal and Non-fatal Drowning

Within a six-year period from 2016-2021, this retrospective cohort study aims to report: 1) the national incidence of fatal and non-fatal drowning incidents attended by the Danish Emergency Medical Services (EMS), 2) Risk factors associated with 30-day mortality, 3) Spatial distribution drowning incidents presented on a map of Denmark stratified for 30-day survival.

Furthermore, the investigators will follow the Utstein Style For Drowning (USFD) recommended guidelines for uniform reporting of data from drowning.

Purpose

The purpose of this study is to establish recommendations towards specific educational, preventative, rescue, or treatment strategies to reduce the number of fatal and non-fatal drowning incidents in Denmark (e.g., campaigns targeting high-risk groups, or fencing, allocating rescue equipment, or establishing lifeguard stations in high-risk areas).

Objectives

The primary objective is to estimate the yearly incidence of fatal and non-fatal drowning incidents in Denmark treated by the Emergency Medical Services from 2016 to 2023. The secondary objective is to explore risk factors associated with 30-day mortality. A directed acyclic graph will be developed \[18\]. For each risk factor, we will test the following hypothesis.

Hypothesis

An increased risk of fatal drowning associated with lack of supervision Drowning patients who are found in the water, where the drowning incident itself was unobserved, are at higher risk of fatal drowning, associated with increased submersion time and EMS response time.

An increased risk of fatal drowning associated with prolonged submersion time Drowning patients with increased submersion time are at higher risk of fatal drowning, associated with more severe hypoxic damage and cardiorespiratory arrest.

An increased risk of fatal drowning associated with alcohol and substance use Drowning patients influenced by alcohol or other substances are at higher risk of fatal drowning because of impaired judgment and coordination.

An increased risk of fatal drowning associated with male sex Males are at higher risk of fatal drowning, associated with increased exposure to water and risk-taking behaviour such as swimming alone, drinking alcohol before swimming alone, and boating.

An increased risk of drowning associated with age Young children (less than five years) are at higher risk of drowning, associated with a lack of swimming skills. However, they tend to be non-fatal as the lapse in supervision is often momentary, allowing for a brief submersion.

Adolescents and young adults (15-25 years) are at higher risk of fatal drowning, associated with risk-taking behaviour.

Adults more than 60 years old are at higher risk of fatal drowning, associated with comorbidities (e.g., heart attacks and STROKE leading to a temporary loss of consciousness in the water) and unwitnessed events.

An increased risk of fatal drowning associated with the type of drowning location Drowning patients in natural bodies of water (e.g., harbours, oceans, lakes) are at higher risk of fatal drowning associated with currents, decreased visibility, uneven terrain, and unwitnessed events.

Study design

A nationwide registry-based study with data from the Danish Prehospital Drowning Data from 2016 to 2023 and follow-up on mortality 30 days after the drowning incident.

Eligibility Criteria:
Inclusion criteria:

* The patient must have been experiencing respiratory impairment from submersion or immersion in liquid AND
* The patient must have been in contact with the Danish EMS.

Exclusion criteria:

* Patients were excluded if it was unclear that the incident involved submersion or immersion with aspiration of liquid (e.g., a patient found dead in the bathtub).
* Patients were excluded if the incident involved submersion or immersion with aspiration, but the patient did not experience respiratory impairment. For example, if the patient was rescued from the water without signs of respiratory impairment, or if the respondent reported "a few coughs" or "voluntary cough".