Discussion

Among people injured in boating incidents, not wearing a PFD, being on a boat that had no safety features and was human-powered increase the chances of being fatally injured compared with those who survived with injuries in a boating incident. They were more likely to be fatally injured in an incident in which the boat capsized, sunk, flooded or swamped, or an incident that involved the person leaving the vessel. Fatalities were more likely in incidents that involved alcohol, took place in the ocean, sound or strait, and between the hours of 00:00 and 5:59.

Our finding of an increased risk of death associated with not using a PFD after controlling for age and sex is consistent with the findings of prior studies. In a matched cohort study, the risk of drowning death was decreased 49% among boaters wearing a PFD compared with those not wearing a PFD.9 The US Coast Guard reports that in 2012 PFD usage in the USA was 22.6% among all boaters, 67.5% among youth under 18 and 9.3% among adults ages 18 and above.12 A 2010 observational study of boats in Washington State reported that PFD usage rates were 30.7% among all boaters and 22–18% among those over the age of 12.13 In Washington State, children ages 12 and under are required to wear a USCG-approved PFD at all times when underway in a boat less than 19 ft in length, unless in a fully enclosed area.14 An emergency ordinance requiring personal floatation device use for all ages on major King County Rivers for the summer season of 2011 was enacted in response to the potential dangers that strong and swift current poses.15 This study confirms the importance of PFD use for surviving a boating incident and supports the need for interventions such as legislation to increase PFD wear.

Our finding of increased risk of death among boaters in a human-powered boat supports findings of recent studies. Among recreational boating fatalities in Ohio, the greatest number of fatalities involved motorboats, but fatality rates were higher for incidents involving smaller boats, such as canoes and rowboats; human-powered boats were associated with a 2.1-fold increased risk of death compared with those in other types of boats.10 The risk of death may be greater among vessels without engines because the operators are more inexperienced than those in motorised boats. Greater lethality may be inherent to a non-motorised vessel since it is often smaller, more prone to capsizing and cannot return to shore as quickly as a motorised boat in the case of emergency or changing water or weather conditions.16 This study supports the need for interventions targeted specifically to those on non-motorised boats, such as life jacket wear and boating safety education.

We found an increased risk of death among boaters who did not have any safety features on their boat. Prior studies including analysis of safety features as a protective factor5 ,17 are descriptive and cannot address the magnitude of the risk factor. It is unclear how safety features such as safety lanyard, safety check, fire extinguisher on board or PFDs on board could directly temper the risk of death during the event phase of the incident. This risk factor may be related to other risk factors, such as recklessness, ignorance, unfamiliarity with boating and alcohol use, that may more directly lead to the incident. There is more to be learned about the characteristics of individuals who do not have safety features on their boat.

Our finding of increased risk of death among boaters in incidents involving alcohol is consistent with prior studies. In 2002, 8.7% of the non-fatal and 22.6% of the fatal boating-related injuries in the USA had alcohol or drugs as a contributing factor.18 In 2012, the US Coast Guard reported that alcohol use was the leading contributing factor in fatal boating incidents, contributing to 16% of the deaths.3 Unlike alcohol use among drivers of motor vehicles, surveyed boaters report that use of alcohol among boaters is a commonly accepted practice.19 However, the estimates of alcohol as a risk factor highlight the associated danger, even if it is not being consumed by the victim, but is consumed by other passengers on the boat.8 All 50 states have legislation prohibiting BUI. However, enforcement of and penalties under to these laws varies widely. Effective prevention strategies should employ lessons learned from motor-vehicle injury prevention strategies, including targeted social awareness of alcohol as a risk factor, as well as increased law enforcement and penalties for BUI.

Increased risk of death among boaters in incidents on the ocean, sound or strait in our study supports previously described observations.2 ,6 ,17 The Canadian Red Cross Society6 posits that boaters on the ocean are subject to greater environmental factors and are at a greater distance from help when an incident occurs compared with smaller and often warmer bodies of water such as lakes and rivers. Water temperatures of ocean and straits in Washington State remain around 40°F year round, increasing the risk of cold water shock and hypothermia. Targeting sea survival messages to boaters on these types of bodies of water may offer an injury prevention strategy.

The increased chance of being fatally injured on the water between midnight and 5:59 has not been identified previously. Over half of the incidents at that time involved alcohol. The nature of boating activities occurring at this time differs from those occurring in the morning, like the social norm of alcohol use in the afternoon and evening. We hypothesise that incidents that occur at this time have greater risk due to operator-related factors such as impaired sighting of hazards, fatigue and environmental factors such as slower access to police or rescue. The increased risk of death at these hours may relate to concomitant alcohol use or that there were few people to report or assist with the incident. Further study is needed to evaluate the factors involved in fatal boating injury and time of day.

We found that those in a fatal boating incident were more likely to have involved capsizing, sinking, flooding or swamping, or a person leaving the boat, a frequently reported observation. The Canadian Red Cross Society6 reported that falling, capsizing and swamping were the most frequent types of incidents among motorised and non-motorised motorboats. Changes made in boat design to decrease risk of capsizing and swamping have likely contributed to a decrease in boating-related fatalities over the past decade.6 Our study highlights the need for prevention strategies such as PFD use in mitigating the risk of death when a person enters the water even in calm waters. Importantly, most fatal and non-fatal incidents occurred when waters were calm. This counters a commonly held misconception among boaters that PFDs only need to be worn during rough conditions. These findings have recently been corroborated by boaters in focus groups.19

Our study has several limitations. Individual-level risk factors collected in the WA BAIRD were limited to age, sex and PFD use. Additional individual risk factors that would be valuable for evaluation include race and ethnicity, which would allow culturally appropriate prevention strategies aimed at specific racial and ethnic groups. In addition, while the BAIRD includes swimming ability, data are only collected for boating fatalities. Swimming ability could help inform whether knowing how to swim is a preventive factor for boating fatality. Ascertainment of boating incidents in the WA BAIRD relied primarily on law enforcement personnel who were required to submit reports when they responded to a boating-related incident. When law enforcement was not involved, the WA BAIRD relied on self-reporting by boat owners. This likely resulted in under-ascertainment of non-fatal events. Prior studies on recreational boating have reported finding an inverse relationship between severity of incident and under reporting.18 This selection bias may have affected the magnitude of the associations we found, with potential underestimation of risk associated with sinking, capsizing or flooding, overestimation of risk associated with not using a PFD or alcohol involvement. Standardisation of ascertainment methods and less reliance on self-reporting would decrease bias but may not be feasible. Case ascertainment will remain a limitation in this field of research.

Our findings substantiate risk factors described in previous descriptive studies of boating deaths and identify several new risk factors. Moreover, we identified boating populations at risk for death compared with injury: those not wearing a PFD and those on non-motorised craft; boats that are human-powered and those without safety features; and environmental conditions, boating on ocean waters and late nights and especially the use of alcohol onboard. Our study findings support legislation and increased law enforcement as critical strategies in addition to educational and environmental interventions to increase PFD use and decrease alcohol use among recreational boaters. Moreover, this study identifies the need to focus on those using human-powered boats. Areas of future research include study of the characteristics of safety features, body of water and time of day in boating incidents. Further study is also needed to evaluate the characteristics of individuals from various racial and ethnic groups in boating incidents.