Alcohol use, aquatic injury, and unintentional drowning: A systematic literature review

Background: Drowning is a global public health issue, and there is a strong association between alcohol and risk of drowning. No previous systematic review known to date has identified factors associated with alcohol use and engagement in aquatic activities resulting in injury or drowning (fatal and non-fatal). Methods: Literature published from inception until 31 January 2017 was reviewed. Included articles were divided into three categories: (1) prevalence and/or risk factors associated with alcohol-related fatal and non-fatal drowning and aquatic injury, (2) understanding alcohol use and engagement in aquatic activities, and (3) prevention strategies. Methodological quality of studies was assessed against the National Health and Medical Research Council (NHMRC). Levels of Evidence and risk of bias was assessed using the Newcastle-Ottawa Quality Assessment Scales. Results: In total, 73 studies were included (57 on prevalence and/or risk factors, 14 on understanding alcohol use, and two on prevention strategies). Prevalence rates for alcohol involvement in fatal and non-fatal drowning varied greatly. Males, boating, not wearing lifejackets, and swimming alone (at night, and at locations without lifeguards) were risk factors for alcohol-related drowning. No specific age groups were consistently identified as being at risk. Study quality was consistently low, and risk of bias was consistently high across studies. Only two studies evaluated prevention strategies. Conclusion: On average, 49.46% and 34.88% of fatal and non-fatal drownings, respectively, involved alcohol, with large variations among studies observed. There is a need for higher quality studies and behavioural basic and applied research to better understand this risky behaviour.


Introduction
Drowning accounts for 7% of all injury-related deaths making it the third leading cause of unintentional death worldwide [1].Detailed examination of the correlates of drowning indicates a strong association between alcohol consumption and drowning risk [2], with studies reporting that alcohol is a contributing factor in approximately 20% of all drowning deaths [3].This increases to 30% [4] and 41% [5] of all deaths related to recreational aquatic activity and river drownings, respectively, and to almost half in certain age groups [5].The true extent of alcohol-related drowning is likely to be higher as alcohol is not routinely ascertained as an autopsy outcome [6].
Although previous research has examined the role of alcohol use and fatal drownings [7] and the attitudes and beliefs underpinning alcohol consumption and aquatic activities [8,9], to the authors' knowledge, to date there has been no systematic review of empirical evidence identifying factors associated with alcohol use and engagement in aquatic activities where injury or drowning (fatal and non-fatal) has occurred.Gaining this knowledge is important as currently there is a lack of national and international research and practice in the area of alcohol-related water policies and water safety initiatives concerning alcohol use around aquatic areas [8].This systematic review aimed to summarise the evidence of studies reporting on unintentional drowning deaths and injury occurring as a result of alcohol use while engaging in aquatic activities.

Method
This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [10].

Eligibility criteria
Observational study designs including prospective and retrospective cohort studies, casecontrol studies, cross-sectional studies, and case series were included.Inclusion criteria were based upon meeting the pre-determined (PECO) population, exposure, comparator, and outcome criteria.Population: people engaged in recreational aquatic activities.Exposure: Alcohol use prior to or during activity.BAC measured, estimated, or other evidence for intoxication.BAC estimated to be greater than zero.Comparator: Those engaged in recreational aquatic activities who did not use alcohol.Outcome: Unintentional fatal or nonfatal drowning death or injury; or, studies aimed at understanding behaviour or evaluating interventions.
Studies were published in English language, and in the peer-reviewed literature.
Where more than one study reported on the same data set, only the study reporting the most information on alcohol involvement was included.Additionally, studies reporting drowning statistics that included intentional (i.e.suicide or homicide) drownings were excluded, as were studies examining alcohol-related drownings outside of the scope of this study (i.e.nonrecreational drownings including occupational drownings and drownings that occurred while attempting to perform a rescue, and injury or drownings where alcohol was a factor but the victim was BAC negative).

Search strategy and study selection
Scopus, PubMed, PsycINFO, SPORTDiscus, and CINAHL were searched up to 31 January 2017 using search terms (see Appendix A supplementary material).Reference lists of reviews and obtained articles were also screened, identifying no additional articles.Endnote X7 citation management software was used, and duplicates removed.Author JK carried out initial title and abstract screening (to exclude ineligible articles).Where information was not available in title and abstract, the full text was retrieved and screened to assess eligibility.Detailed full-text screening of remaining articles was carried out by authors JK and KH (Figure 1).Any disagreements between reviewers were resolved through discussion and consultation with AEP.

Data extraction and quality assessment
Data synthesis was performed by dividing the articles into three categories (1) prevalence and/or risk factors associated with alcohol-related fatal and non-fatal drowning and aquatic injury, (2) understanding alcohol use and engagement in aquatic activities, and (3) prevention strategies.Methodological quality of all included studies was assessed using the National Health and Medical Research Council (NHMRC).Levels of Evidence [11] and risk of bias was assessed using the Newcastle-Ottawa Quality Assessment Scale [12].Studies were assigned 'star' ratings according to each quality criterion.Case series and case control studies could attain a maximum of nine stars, case-control studies could attain a maximum of six, and cross-sectional studies could attain a maximum of 10 stars.Information regarding population, data source, prevalence, activity prior to drowning, and associated risk factors was extracted for the studies in the prevalence and/or risk factors category.Information regarding the methodological quality, population and setting, and results were extracted from the studies on understanding alcohol use during recreational aquatic activities.In studies evaluating prevention strategies, information regarding location, prevention strategy, and results of the evaluation were extracted.The final search generated 74 studies to be included in the qualitative synthesis.NVivo 11 was used to facilitate coding.Overall mean alcohol involvement in fatal and non-fatal drowning and means clustered by country were calculated to summarise prevalence data.

Results and Discussion
Summaries of included studies on prevalence and/or associated risk factors are presented in Tables 1-3, studies in understanding alcohol use and aquatic activities are presented in Table 4, and studies on prevention strategies are presented in Table 5. Assessment of risk of bias among the included studies [12] revealed that only six studies in each of the three areas achieved a star rating of 4-or 5-, with the 23.6% of studies attaining a 3-star rating, 34.7% attaining a 2-star rating, and 23.3% attaining 1-or 0-star rating.This indicated generally high risk of bias of the studies in all domains.A quality assessment [11] of the included studies indicated that most studies attained the lowest possible rating (a grade of IV) with only a small number of studies holding a grade of III.
Eleven studies [13,17,21,25,[27][28][29][30][31][32][33] identified age-related trends in prevalence of alcohol involvement in fatal drowning; however, these varied considerably, and a conclusion could not reliably be drawn as to the existence of an overall trend.One study [34] found alcohol-related drownings, as a result of falls and boating incidents, were more common in those older than 35 years.Two studies [35,36] identified beaches and two studies [21,37] identified rivers as locations where alcohol-related drownings were most prevalent.Risktaking behaviours including deliberately jumping into a river, violating safety rules, and swimming in unauthorised areas were also identified as being more likely to precede alcoholrelated drownings in two studies [5,38].Another study found alcohol involvement in drowning deaths among off-duty UK Army personnel to be at a higher rate than the general population [39].A single study [40] reported a decrease in alcohol-related drowning deaths, with an 81% decrease in the 21-year period until 1995 in King County, Washington State.This decrease was partially explained by an overall reduction in severe submersion episodes and less alcohol use around water; however, about half of the decrease was unexplained.
Another study [41] found 53% of drownings deaths in Alaska that occurred while the victim was alone were alcohol-related, compared to 26% of cases where there were witnesses.
Three studies found alcohol-related drowning to be more prevalent in watercraft/boat users compared to swimmers [42][43][44].Another study [45] showed the risk of boating incidents increases as BAC increases, with the risk being 10 times higher at 1.0% and 20 times higher at 1.5% BAC.Two studies [43] found that fall-related drownings were also more likely to be alcohol-related (and involve higher BAC levels) than swimming-related drownings.A study [46] examining alcohol-related recreational boating incidents found alcohol-related fatalities were most prevalent in canal boats (54%), followed by motor boats (32%).A case-control study [44] found recreational boating passengers were more likely to be BAC positive in the fatality group (68% vs. 48%) and that the risk of death increases as BAC increases; OR=1.3 at 10mg/dl (95% CI [1.2, 1.4]), 3.7 at 50mg/dl (95% CI [2.8, 4.7]), 10.4 at 100mg/dl (95% CI [6.9, 15.7]) and 52.4 at 250 mg/dl (95% CI [25.9, 106.1]).The control group was a stratified random sample of boaters matched by location to the fatality subjects.Four studies [23,30,38,47] identified alcohol-related deaths may have been prevented if lifejackets were worn; or, that death was more likely when safety equipment or lifeguards were not present.One study [30] examining fatal drowning identified proportionally more instances of lifejackets being available but not used and proportionally less instances of lifejacket use when alcohol was involved compared with drownings not involving alcohol.

Non-fatal drowning. Seven studies reported on non-fatal drowning (Table 2).
Prevalence rates of alcohol involvement in non-fatal drowning ranged from 21.25% to 74.14% (M = 34.87%,SD = 16.37%,95% CI [7.56%, 62.17%]).Three [48][49][50] of the studies conducted further analyses of the factors associated with these alcohol-related incidents.A case-control study [48] found alcohol use during the most recent aquatic activity was four times more likely in those who sustained a spinal injury than the non-injured controls (OR = 4.0, 90% Cl [1.1, 15.0]).A study [49] examining Barbados hospital records found alcohol to be involved in 13 visitor and five resident non-fatal drownings; however, the difference was not statistically significant.A study [50] examining surf lifesaving resuscitations found 89% of incidents involving alcohol were related to immersion; involvement of alcohol was not significantly different between gender and did not significantly reduce the likelihood of resuscitation (79% success rate when alcohol involved; 64% success rate when alcohol not involved).

Combined fatal and non-fatal drowning.
Two studies [51,52] compared alcohol involvement in fatal and non-fatal submersion cases (Table 3).One study [52] found fatal cases were significantly more likely to have alcohol involved than non-fatal cases (OR 2.35).
Fatal and non-fatal submersions were most likely to have alcohol involved in the 25-44 age group followed by the 21-24 age group [52].Another study [51] examined alcohol-related fatal and non-fatal drowning victims using hospital records and found 93.3% of victims were male, the average age was 36, and 20% were fatal.
In sum, the prevalence of alcohol involvement in fatal and non-fatal drownings varied considerably, with the range for alcohol involvement in drowning between studies being more than 67 percentage points (fatal drowning) and 52 percentage points (non-fatal drowning).Potential explanations for this disparity are that studies use different criteria and methods of assessment for considering alcohol involvement or do not consistently assess alcohol involvement.While all included studies recorded a percentage of drownings where alcohol was involved, there was considerable discrepancy between whether the 0-14 year age group or cases with unknown alcohol involvement were included in the calculations.These rates are also likely to underestimate the extent of the issue as alcohol involvement is unknown or not recorded in all cases, and not all non-fatal drownings are reported.In the studies that compared fatal and non-fatal drowning based on alcohol involvement, it emerged that rates of alcohol use were higher in fatal drownings.Lifejackets were identified as a possible prevention measure for alcohol-related drowning deaths and boating as a greater risk factor than swimming.Aside from the one study reporting BAC and increasing risk in boaters [45], due to the disparities in how prevalence of alcohol involvement in drowning and BAC are reported, we were unable to identify the BAC where risk starts to increase during aquatic activities generally.While 0.05% BAC is one of the most commonly used indicators due to its association with increased risk of motor vehicle accidents and poorer motor skills and judgement, it is unclear if this level is an appropriate guideline for drowning prevention [5].
To allow for international comparison, more population-based research using a consistent reporting framework should be conducted, and it is important that reports on fatal and nonfatal drownings include information on alcohol use.

Understanding alcohol use and aquatic activities
Fourteen studies were included (Table 4).Four studies [53][54][55][56] reported higher rates of alcohol use during recreational aquatic activities in males compared to females, with one study [53] finding males with high water confidence were significantly more likely to have consumed alcohol in the two hours prior to engaging in aquatic activities (other than boating) than those with low water confidence.The effect of confidence on alcohol use was not significant in females.Another study [57] found alcohol use within 12 hours of diving was more common among more frequent divers, with 58.4% of divers who had consumed alcohol within 12 hours of diving reported having sustained injuries, compared with 56.1% who did not use alcohol.
Despite no age-related trend emerging across the studies, a study [54] found younger men (16-30 years) consumed more alcohol than older men (as did McCool et al. [55]; 16-29 years), males were significantly more likely to have consumed alcohol when swimming alone than with others (15% vs. 4%), and men were significantly more likely to consume alcohol while swimming at night than in the day (38% vs. 32%).Males were also significantly less likely to swim where a lifeguard was present when they had consumed alcohol during that day, and of the participants who boated without using a lifejacket, males were significantly more likely to have consumed alcohol (44% vs. 30%) [54].Similarly, in a sample comprising 85% males [58] low or no lifejacket use among recreational boaters was associated with alcohol use (RR = 1.11; 95% CI [1.01 -1.20]).Another study [59] examined behaviours around boating retrospectively and found 44.8% of participants reported using alcohol while boating in the previous summer.A majority (69.9%) reported using a designated boat operator (DBO) in their last recreational boating session, but despite 95.0% of the sample demonstrating a knowledge of drinking and boating laws, 24.5% reported that their DBO used alcohol in their last recreational boating session.Further, 57.6% reported alcohol increases enjoyment of water sports.
A study [60] that surveyed boaters at boat ramps found 76.2% of boaters reported they had consumed alcohol while boating previously.Half (50%) correctly indicated that an intoxicated person is 10 times more likely to drown than a sober person.Further, 83% correctly indicated that it is illegal to operate a watercraft while under the influence of alcohol in every US state and 84.2% reported the correct legal BAC of 0.08% while operating a watercraft in Illinois.In a survey of registered boat owners in Massachusetts [61], it was found that 45.2% of participants were not aware of federal laws restricting alcohol use while boating.Only a small number of participants (5%) indicated it would be safe for a boat operator to consume three or more drinks, and 24% indicated it would be safe for a passenger to do so.
In an Australian study [62], it was found that 82% of recreational fishers reported never drinking alcohol while engaging in recreational fishing, with respondents born in Asia being less likely to consume alcohol.Another Australian study [8] found that positive attitudes toward drinking and swimming and perceived approval by important others predicted intention to swim while under the influence of alcohol.Further, a UK study [63] found that the UK government recommended weekly alcohol units for divers were more often exceeded by older divers, and younger divers more frequently engaged in binge drinking.Additionally, 18.5% of participants reported diving when they considered themselves 'unfit' (due to intoxication) to drive a car, 22.9% of participants had witnessed a diving incident that they believed was attributed to alcohol, and 38.3% of participants reported their dive clubs as having a responsible attitude toward alcohol.
In summarising these findings, several trends were evident.Consuming alcohol prior to aquatic activities is more prevalent in males than females, which may be due to higher levels of water confidence or familiarity with the aquatic behaviour (e.g., diving, boating).
Further, males take more risks around water when drinking (e.g., swimming alone, not wearing a lifejacket).An Australian study also identified that males' attitudes and social pressure towards drinking and swimming may also play a role in intentions to undertake the behaviour [8].There was also evidence of a lack of understanding regarding the effects of alcohol use and drowning, and the legal requirements regarding alcohol use when operating watercrafts/boats.Overall, although there is some understanding of the demographic factors influencing alcohol use and aquatic activities, there is limited understanding of the psychological and behavioural factors contributing to this risky behaviour.Given that alcohol-related drownings are preventable, and that social and motivational factors have been found to influence intentions to drink alcohol and swim in prior research [8], more research is needed to understand the psychological factors that may guide individuals' decisions to engage in safety compromising behaviours around water.Research of this nature can inform development and evaluation of theory-based psychological and behavioural interventions and help identify policy measures that may be effective in reducing alcohol use during aquatic activities.

Prevention strategies
Two studies related to prevention strategies were included (Table 5).One study [64] sought to evaluate anti-alcohol legislation restricting boat operator alcohol consumption aimed at reducing boating accidents using a case-control design.Alcohol involvement contributed to operator fault in non-fatal accidents, but not in fatal accidents.However, alcohol use was found to be a significant determinant of the severity of boating accidents, with accidents involving alcohol more likely to be fatal.It was therefore recommended that prevention strategies target passengers in addition to boat operators.The second study [65] evaluated the effect of reductions to the minimum legal drinking age on drowning among young adults, finding no significant association.The studies were conducted in 1993 and 1998, respectively.Given the prevalence estimates reported in the previous section, that prevention studies showed no effects on drowning and that there have been no studies evaluating prevention strategies in the past 19 years, this review highlights a significant gap in the literature.Development and evaluation of theory-based interventions, which have been shown to be effective in other risk behaviour contexts, are a high priority for research.

Conclusion
Overall, data from the current set of studies highlights alcohol consumption as a risk factor for drowning and may underestimate the breadth of this concern for public health and fail to completely identify factors associated with this risky behaviour [5].Evidence of this nature is of key importance for public health as it can be used to identify and to set priorities in terms of prevention and health promotion as well as contribute directly into existing programs to improve effective tailoring of program messages and promotion strategies to influence behaviour change.Given the expanse of research in this area, this review makes an important contribution to knowledge of the factors linked with alcohol-related drowning and aquatic injury.Despite the strengths identified, current findings must be considered in light of some limitations.First, searches were limited to English language published literature, which would not have included studies that have been conducted in the area and not-published in English journals.Second, to prevent inflated estimates of prevalence, studies that did not explicitly indicate drowning as unintentional or did not make the role of alcohol clear were excluded.Third, the overall quality of the included studies was low, and the risk of bias was high.Low levels of methodological quality impose limits on the reliability of findings, the inferences that can be made, and the generalisability of the findings.In particular, data reporting in epidemiological studies was highly variable presenting challenges in deriving prevalence rates and associated risk factors, and in determining criteria for which drownings are likely to be influenced by alcohol.A further limitation in the area of prevention was the lack of intervention and controlled studies targeting particular prevention strategies.
Overall, alcohol consumption is known to increase drowning risk.While prevalence rates vary, we identified that on average 28.10% and 34.87% of fatal and non-fatal drowning, respectively, involved alcohol (Table 6).Current findings indicate a lack of awareness of the impact of alcohol on drowning risk and this should be a consideration for drowning prevention advocates in the future.Future research must employ a consistency in study design to allow comparison between studies, including confirming an appropriate BAC for determining contribution for aquatic-based incidents.The development, implementation, and evaluation of strategies based in psychological and behavioural theory to reduce alcoholrelated drowning and aquatic injury are a priority to reduce further loss of life.• Formal training (vs.informal training) and boating experience was associated with an increase in drinking while boating.• Those with formal training were also less likely to say that alcohol greatly increases their risk of drowning or injury.• It is suggested that this may be due to increased confidence associated with training and experience and an underestimation of the risks.

Burhans et al. (2013) [84]
• Sampling frame: students in an engineering class at a Midwest University.• Sampling method: convenience • Recruitment method: not specified • Administration method: internet-based questionnaire.
• 3/IV • 21% of males and 10% of females reported having consumed alcohol within two hours of boating in the past year.• 23% of males and 9% of females reported having consumed alcohol within two hours of water-related activities other than boating in the past year.• Males with higher water confidence (25% vs. 8%; p = .01)were significantly more likely to have consumed alcohol in the two hours prior when engaging in other water activities.
• Administration method: face-to-face interview following structured questionnaire.
• Response rate: 97% of cohort followed-up at current time point.
This effect was not significant with regards to boating or in females.• Alcohol consumed within 2 hours of a water activity was associated with a near-drowning experience in females but not in males.(2000).
• 33% of men and 23% of women reported consuming alcohol on their most recent day of aquatic activity in the past month.• Younger men consumed more alcohol than older men, and men consumed consistently more alcohol than women.
• Men were significantly more likely to have consumed alcohol when swimming alone (15% vs. 4%) and significantly more likely to consume alcohol while swimming at night (38% vs. 32%).• Of the participants who boated without using a lifejacket, men were significantly more likely to have consumed alcohol (44% vs. 30%).
• Men only were significantly less likely to swim where a lifeguard was present when they had consumed alcohol on the day.• UK government recommended weekly alcohol units for divers were more often exceeded by older divers, but younger divers more frequently engaged in binge drinking.• 18.5% of participants reported diving when they considered themselves unfit (due to intoxication) to drive a car.• 22.9% of participants had witnessed a diving incident that they believed was attributed to alcohol.• 38.3% of participants reported their dive clubs as having a responsible attitude toward alcohol.(1993) [64] USA: all 50 states 1987-1988 Data Source: US Coast Guard (all fatal accidents are reported, and law requires all non-fatal accidents with property damage exceeding $500 be reported) Examined factors relevant to anti-alcohol legislation as a prevention strategy for reducing recreational boating accidents.Results: Anti-alcohol legislation was aimed at reducing boating accidents by reducing alcohol consumption while boating.Particularly, alcohol involvement contributed to operator fault in non-fatal accidents, but not in fatal accidents.Alcohol use was found to be a significant determinant of the severity of boating accidents.That is that accidents involving alcohol are more likely to be fatal.It was also found that while alcohol involvement is a causal factor in boating fatalities, it does not necessarily cause the operator to be at fault.It is recommended that preventative legislation be aimed as both boat passengers and operators.

Table 1
Relevant articles identifying prevalence and/or risk factors of fatal drowning while under the influence of alcohol (n = 48) sorted by country

Table 2
Relevant articles identifying prevalence and/or risk factors of non-fatal drowning or aquatic injury while under the influence of alcohol (n=7) sorted by country

Table 3
Relevant articles comparing prevalence and/or risk factors between fatal and non-fatal drowning or aquatic injury while under the influence of alcohol (n = 2)

Table 4
Relevant articles aimed at understanding alcohol use and aquatic activities (n = 15) 1% of males and 23.7% of females reported consuming alcohol in the two hours prior to entering the water during their most recent visit to the surf beach.3 standard drinks or more were indicated in 18.9% of males and 5.7% of females.

Table 5
Relevant articles discussing proposed prevention strategies for alcohol use and aquatic activities (n=2)

Table 6
Bierens et al. (1989)f lowering or raising the minimum legal drinking age (MLDA) on adolescent (and adjacent age) drowning(15-23 years).Results: No significant association between MLDA and drowning was detected in any of the two-year age groups studied.Concluded that changes to MLDA is not a useful strategy in drowning prevention.Weighted mean percentages of fatal and non-fatal drowning involving alcohol by country.Giertsen (1970)was excluded from the above calculations due to examining only BAC positive cases.Levy et al. (2004)andBierens et al. (1989)examine both fatal and non-fatal cases.Therefore, respective statistics from these studies were included in both fatal and non-fatal calculations.Please note that total prevalence rates have been calculated across countries and studies for the included studies.