Hospitalizations for drowning dropped 51% between 1993 and 2008, according to the results of a study based on data from the Nationwide Inpatient Sample.

The number of hospitalizations fell from an estimated 3,623 in 1993 to 1,781 in 2008. During the same period, the estimated annual incidence rate of pediatric hospitalizations associated with drowning declined 57% – from 4.9 to 2.1 per 100,000, according to findings published online Jan. 16 in Pediatrics (2012;129:1-7).

"Our study provides national estimates of pediatric drowning hospitalizations that can be used as benchmarks to inform drowning prevention efforts and to help target interventions to high-risk areas. Given the significant burden of drowning in both real and human costs, additional monitoring of pediatric drowning is needed," wrote Stephen M. Bowman, Ph.D., of the center for injury research and policy at Johns Hopkins University in Baltimore, and his coinvestigators.

"This is an important finding that provides some evidence of a true decrease in drowning incidents."

The researchers used administrative discharge data from the 1993 to 2008 Nationwide Inpatient Sample (NIS). The NIS is created from state inpatient databases provided by public/private statewide data organizations from participating states. The NIS is the largest, longitudinal, all-payer inpatient care database in the United States, with an average of 8 million hospitalizations from approximately 1,000 hospitals each year, the researchers noted. The NIS approximates a 20% stratified random sample of all short-term U.S. community hospitals.

Eligibility for this study was limited to children and adolescents who were aged 0-19 years at admission and who were hospitalized with a primary or secondary ICD-9-CM diagnosis code for drowning injury. Patients who died while hospitalized were included.

The circumstances of drowning were determined based on the external cause of injury code when possible. The circumstances of drowning injury were categorized into five groups: recreational swimming and diving, drowning in bathtubs, other drowning activities, all other codes, and missing. For the incidence rate calculations, the investigators used U.S. Census estimates for the national civilian population at midyears during this time interval. External cause of injury codes were missing for up to 55% of hospitalizations before 1997. For this reason, the investigators compared 2-year aggregate data for the years 1998-1999 and 2007-2008 to evaluate changes in drowning mechanism and intent over time.

Drowning characteristics typically differ by age and sex. Young children (less than 4 years of age) have the greatest mortality rate from drowning and are more likely to drown while bathing or falling into water, the authors noted. Older children are more likely to drown while swimming in open water. In addition, males are four to six times more likely than females to experience a drowning injury, because of factors such as overestimation of swimming ability and greater use of alcohol by adolescent males, Dr. Bowman and his associates said.

The hospitalization rates declined significantly for all ages and for both sexes. However, the rate for males remained greater at each point in time. The total annual hospital days also declined from an estimated 14,570 days in 1993 to approximately 6,295 days in 2008. However no trend in mean hospital length of stay was observed.

"Consistent with decreases in pediatric drowning mortality, we observed a significant decline in the rate of pediatric drowning hospitalizations, primarily because of decreases in the South and West. This is an important finding that provides some evidence of a true decrease in drowning incidents, rather than a possible shift from fatal out-of-hospital drowning to nonfatal in-hospital cases," Dr. Bowman and his associates wrote. Hospitalization rates decreased significantly across all geographic regions of the United States, although the greatest decline in drowning hospitalization rates occurred in the South. The overall drowning rate fell from 7.5 hospitalizations per 100,000 in 1993-1994 to 3.5 per 100,000 in 2007-2008 in this region.

"Between 1998-1999 and 2007-2008, we observed a significant change in drowning hospitalization rates for selected ages and mechanisms," they wrote. Overall, there was a significant decline (40%) in bathtub-related drowning hospitalizations in children aged 0-4 years. Drowning hospitalizations due to swimming and diving decreased by nearly half in older children aged 10-14 years.

"Reductions in bathtub drowning hospitalizations among the youngest children may reflect a response to targeted injury prevention efforts that have been aimed at parents and caregivers of young children, encouraging increased vigilance in supervision.

"Interestingly, we did observe a decrease in the rate of in-hospital deaths over the 14-year period, although the in-hospital case fatality did not change significantly," the researchers noted. In-hospital mortality declined 42% from an estimated 359 deaths in 1993 to 207 deaths in 2008. "Although improvements in treatment might be having an impact on survival, it is not clear from these data what level of neurologic functioning survivors may have. An alternate explanation is that better decision making in the prehospital period may be resulting in more pronouncement of death in the field for unsurvivable cases."

The study was funded by the National Institutes of Health. Dr. Bowman and his associates reported that they have no relevant financial disclosures.

Drowning Hospitalizations Halved Between 1993 and 2008