Link between pre-existing health conditions and drownings in Canada: a 10-year cross-sectional analysis

Context: Drowning accounts for hundreds of preventable deaths in Canada each year, but the impact of pre-existing conditions on the risk of drowning death is unknown. We aimed to describe the prevalence of pre-existing conditions among drowning victims in Canada and to assess the risk of drowning among individuals with common pre-existing conditions. Methods: We reviewed all accidental drownings in Canada (2007-2016) identified in the Canadian Drowning Prevention Research Centre database. For each drowning, we determined whether the person had any pre-existing conditions and whether these conditions contributed to the drowning. We calculated the relative risk (RR) of drowning stratified by age and sex for each preexisting condition using the Canadian Chronic Disease Surveillance System database. Results: During the period 2007 to 2016, 4288 people were victims of accidental drowning in Canada, and one-third of them had pre-existing conditions. A pre-existing condition contributed to drowning in 43.6% (n = 616) of cases. Drowning occurred more frequently in those with ischemic heart disease (RR 2.7, 95% confidence interval [CI] 2.5-3.0) and seizure disorder (RR 6.3, 95% CI 5.4-7.3) but less frequently in those with respiratory disease (RR 0.12, 95% CI 0.10-0.15). Women aged 20-34 years with a seizure disorder were 23 times more at risk than the age- and sex-matched cohort (RR 23, 95% CI 14-39). In general, among those with preexisting conditions, drowning occurred most often in a bathtub (RR 5.9, 95% CI 4.8-7.0) or in unattached individuals (RR 1.99, 95% CI 1.32-2.97) and less often in men (RR 0.92, 95% CI 0.88-0.95) and those who had been drinking alcohol (RR 0.72, 95% CI 0.65-0.80). Interpretation: The risk of drowning is higher in the presence of certain pre-existing conditions. Drowning prevention strategies need to be developed for specific pre-existing conditions and age groups. Initial prevention strategies should focus on seizure disorders and drowning that occurs in the bathtub.