Friday, May 31, 2013

An Essay on the Epidemiology of Drowning

The discussion of drowning epidemiology is often confusing and misleading. I will attempt to break it down in a meaningful way.

Drowning is defined as "the PROCESS of experiencing repiratory impairment as a result of submersion/immersion in a liquid medium". Drowning can only have 3 outcomes, 1-mortality (death), 2-Survival with morbidity (brain damage), 3- Survival without morbidity (no brain damage). There is no such thing as "near-drowning".

Drowning is often quoted as "the 3rd leading cause of unintentional injury death worldwide". This comes from the World Health Organization (WHO) Global Burden of Disease 2004 update. First, the WHO only logged 388,000 drowing deaths worldwide in 2004. More than 95% of these deaths occur in low and middle income countries (LMIC), where under-reporting is the rule more than the exception. When a person drowns in a remote area, anectdotal evidence suggests that they are simply buried, but never make it to the hospital where the data collection occurs. Compare that to the leading cause of accidental injury death worldwide-motor vehicle collisions (MVC's, AKA Road Traffic Acidents). Nearly every person that is in a serious car collision either gets taken to the hospital (since there are probably other cars around) or at least alert law enforcement or other authorities who can document the incident.

The most conservative estimate is that for every 1 drowning death that occurs, an additional 4 drowning deaths go unrecorded. 388,000 x 4 = 1.55 million. Add that to our original 388,000 and you get 1.94 million drowning deaths per year. But what about all of those non-fatal drowning incidents, some of which result in serious brain damage? For every drowning death, there are an additional 4 to 10 nonfatal drowning incidents. So if we take the most conservative estimate 1.94 million x 4 = 7.76 million drowning incidents per year!!!! This doesn't include floods, tsunamis, natural disasters, or boating accidents, but I won't go there now.

So, lets just go back to that small 388,000 number and break it down a little bit. The WHO says that it is the 3rd leading cause of unintentional injury death. Worldwide, about 2,270 children die every day from ALL causes of unintentional injury. The number 1 cause is car crashes (22.3%) and number 3 is drowning (16.8%). So that begs the question, what is number 2 (31.1%)? Other. Thats right, "Other", which includes categories such as smothering, asphyxia, choking, animal and venomous bites, hypothermia, hyperthermia, and natural disasters. I'd be willing to bet that there a few natural disaster drowning deaths in that category from tsunamis, floods, hurricanes, etc... Hurrican Sandy killed 117 people, nearly a third from drowning. So if the #2 cause of unintentional injury death is "Other", I move it down to #3 and always teach that Drowning is number 2 behind MVC's.

But what about here in the US? Based on the 2010 CDC data, Drowning is the #1 cause of unintentional injury death for children 1-4 (436), followed by MVC's (343). In 5-9 year olds, it is the #2 cause (134) behind MVC's (354). Finaly, in 10-14 year olds, drowning is again #2 (117) behind MVC's (452).

So, I would offer that Drowning, even if we take the really low under-represented numbers, is the #2 cause of unintentional injury death worldwide and in kids uner 14 in the US. It is the #1 cause of unintentional injury death in the US in kids 1-4. So lets give drowing the attention, care, and research that it deserves.

Written by Justin Sempsrott, MD