Burden and Causes of Unintentional Injuries
This section provides a brief outline of the burden of unintentional injuries and then reviews the available evidence about known and potential causes of such injuries.
Burden of Unintentional Injuries
Worldwide, unintentional injuries accounted for more than 3.5 million deaths in 2001, or about 6 percent of all deaths and 66 percent of all injury deaths. Unintentional injuries were also responsible for more than 113 million DALYs in 2001, or about 8 percent of all DALYs and some 70 percent of all injury DALYs. More than 90 percent of unintentional injury deaths occurred in low- and middle-income countries (LMICs), accounting for around 7 percent of all deaths in those countries. Similarly, more than 90 percent of DALYs that were attributed to unintentional injuries occurred in LMICs, accounting for about 8 percent of all DALYs in those countries. Injury death rates per 100,000 population were higher in LMICs (62 per 100,000) than globally (57 per 100,000).
Males accounted for almost two-thirds of the deaths attributed to unintentional injuries in LMICs in 2001, with rates of both injury death and DALY losses higher among males than females (table 39.1). Compared with other age groups, young people age 15 to 29 accounted for the largest proportion of deaths from unintentional injuries in LMICs (figure 39.2).
[Figure
39.2]
[Table .]
RTIs accounted for the greatest burden of deaths from unintentional injuries in LMICs in 2001, or about 34 percent of the total burden, and the greatest burden of DALYs from unintentional injuries in LMICs in 2001, accounting for 28 percent of the burden (figure 39.1). Whereas young people age 15 to 29 years accounted for the highest proportion of all unintentional injuries, those age 45 to 59 accounted for the highest proportion of injuries from poisonings, while those age 70 to 79 accounted for the highest proportion of injuries from falls (figure 39.2).
Economic Burden of Unintentional Injuries
Estimates of the burden of unintentional injuries as measured in terms of economic costs are almost nonexistent. The best estimates available are for RTIs. Using road crash costs from 21 developed and developing countries, the Transport Research Laboratory Ltd. finds that the average annual cost of road crashes was equivalent to about 1.0 percent of gross national product in developing countries, 1.5 percent in transition countries, and 2.0 percent in highly motorized countries. The annual burden of road crash costs is about US$518 billion globally and about US$65 billion in LMICs, exceeding the total annual amount these countries receive in development assistance (Jacobs, Aeron-Thomas, and Astrop 2000).
Causes of Unintentional Injuries in LMICs
As in the case of most diseases, unintentional injuries are caused by multiple factors. The traditional epidemiological paradigm of host, vector, and environmental factors that in combination contribute to the incidence of disease has been adapted and applied in determining the causes of unintentional injury. However, this paradigm has been extended to consider each factor in relation to the time of the injury—that is, factors operating before, during, and after the injury that might be associated with both its incidence and its severity (Haddon 1968). Although the matrix, called the Haddon matrix, was initially developed to address the problem of RTIs only, it provides a comprehensive framework in which researchers can consider the multitude of factors that may play a role in the causal injury pathway, as outlined in table 39.2.
[Table .]
In the past two decades, the evidence base for the identification of risk factors for unintentional injuries in high-income countries (HICs) has increased dramatically as the number of injury researchers and research institutions has increased. However, because of the paucity of injury researchers and research institutions in LMICs, the evidence base for the identification of risk factors for unintentional injuries in these countries is growing more slowly.
Although knowledge about risk factors for injuries in HICs may also be relevant for LMICs, the material presented in the following section focuses on information that has been obtained from studies in LMICs. However, the section also considers the extent to which information obtained from studies conducted in HICs may be relevant.
Risk Factors for Road Traffic Injuries
The increasing volume of traffic is one of the main factors contributing to the increase in RTIs in LMICs. Motorization rates rise with income (Kopits and Cropper 2005), and a number of LMICs experiencing growth have seen a corresponding increase in the number of motor vehicles (Ghaffar and others 1999). In some LMICs, this growth has been led by an increase in motorized two-wheeled vehicles, one of the least safe forms of travel, which has resulted in concurrent increases in related injuries (Zhang and others 2004).
The rapid growth in motor vehicles in many LMICs has not been accompanied by improvements in facilities for these road users or by facilities that respond to the continued predominance of nonmotorized traffic (Khayesi 2003). Many of the technical aspects of planning, highway design, traffic engineering, and traffic management that are the hallmarks of transportation systems in many HICs are absent in LMICs, which need to plan for a level of heterogeneity in traffic that HICs do not encounter (Tiwari 2000).
Studies undertaken primarily in HICs show a strong relationship between the increase in vehicle speeds and increased risk of crash and injury, both for motor vehicle occupants and for vulnerable road users, particularly pedestrians (European Road Safety Action Program 2003). This relationship is likely to be true for LMICs, and indeed, data obtained from routinely collected police reports in a number of LMICs show that speed is listed as the leading cause of road traffic crashes, accounting for up to 50 percent of all crashes (Afukaar 2003; Odero, Khayesi, and Heda 2003; Wang and others 2003).
Several case-control studies in HICs have confirmed the role of alcohol in the increasing risk of road crashes (Peden and others 2004). Studies conducted in LMICs showed that drivers had consumed alcohol in 33 to 69 percent of crashes in which drivers were fatally injured and in 8 to 29 percent of crashes in which drivers were not fatally injured (Odero and Zwi 1995). Alcohol consumption by pedestrians also increases their risk of injuries in HICs; moreover, in at least some LMICs, more than 50 percent of fatally injured pedestrians had consumed alcohol (Peden and others 1996).
Other factors that increase the risks of road crashes in HICs include fatigue, use of hand-held mobile telephones, and inadequate visibility of vulnerable road users (Peden and others 2004), all of which are equally likely to increase risks in LMICs. Indeed, a recent case-control study from China shows that the risks of a crash doubled with chronic sleepiness on the part of the driver (G. F. Liu and others 2003), and surveys of commercial and public road transport in a number of African countries have shown that drivers often work long hours and go to work exhausted (Mock, Amegashi, and Darteh 1999; Nafukho and Khayesi 2002). Studies in Malaysia clearly show that motorcyclists who use daytime running lights have a crash risk about 10 to 29 percent lower than those who do not because of their greater visibility (Radin Umar, Mackay, and Hills 1996).
Road- and vehicle-related factors may also increase the risk of crash involvement. Specific factors related to road planning include traffic passing through residential areas, conflicts between pedestrians and vehicles, schools located on busy roads, lack of median barriers to prevent dangerous passing on two-lane roads, and lack of barriers to prevent pedestrian access onto high-speed roads, although few studies have specifically examined the risks associated with those factors (Ross and others 1991).
Although the severity of crash injuries is related to in-vehicle crash protection, evidence indicates that many engineering advances found in vehicles in HICs are not present in vehicles in LMICs (Odero, Garner, and Zwi 1997). Perhaps one of the most important factors contributing to injury severity relates to crash protection for vulnerable road users. However, few HICs, let alone LMICs, require the fronts of cars or buses to be designed in a way that would protect vulnerable road users (Mohan 2002).
A significant risk factor for increased severity of injuries of users of motorized two-wheeled vehicles is riders' failure to use motorcycle helmets (B. Liu and others 2004). Studies in a number of Asian countries have shown that failure to use helmets, use of nonstandard helmets, and use of improperly secured helmets are not uncommon, even in countries with mandatory helmet laws (Conrad and others 1996; Kulanthayan and others 2000). Failure to wear helmets is also a risk factor for increased injury severity among bicyclists (Attewell, Glase, and McFadden 2001). Although the failure to use seat belts is a significant risk factor associated with injury severity among vehicle occupants, many LMICs have no requirements for seat belts to be fitted or used (Peden and others 2004).
Studies in HICs suggest that roadside hazards, such as trees, poles, and road signs, may contribute to between 18 and 42 percent of road crashes and increase injury severity (Kloeden and others 1998), although the extent to which this is also true in LMICs has not been determined.
Risk Factors for Poisonings
The literature on poisonings in LMICs includes comprehensive information about intentional poisonings; significant information about occupation-related poisonings, especially pesticide poisonings; and a growing body of information about lead poisoning. Each of these types of poisoning is covered elsewhere in this book. This chapter focuses on risk factors for other types of poisoning in LMICs, and, in particular, focuses on risk factors for poisonings in young children.
The literature's focus on risk factors for childhood poisoning probably reflects the fact that child poisoning victims are seen more often than adults in most hospital settings (Ellis and others 1994; Nhachi and Kasilo 1992). This fact is in stark contrast to the data presented earlier, which clearly show that middle-aged individuals sustain the vast majority of deaths and DALYs from poisonings in LMICs. Those numbers no doubt reflect the importance of work-related poisonings.
Young males consistently appear to be at higher risk of poisonings than females (Ellis and others 1994; Fernando and Fernando 1997; Soori 2001). The most common agents involved in childhood poisonings are paraffin (or kerosene) and other household chemicals; pesticides; and various plants or animals, including snakes (Fernando and Fernando 1997).
Several case-control studies in LMICs indicate the importance of a number of sociodemographic risk factors, including young parents, residential mobility, and limited adult supervision of children (Azizi, Zulkifli, and Kasim 1993; Soori 2001). The studies also suggest that previous poisoning may be a risk factor (Soori 2001). Another important factor seems to be storage, including the number of storage containers used in the residence; the use of nonstandard containers for storage (for example, beverage bottles for storing kerosene); and the storage of poisons at ground level (Azizi, Zulkifli, and Kasim 1993; Chatsantiprapa, Chokkanapitak, and Pinpradit 2001; Soori 2001).
Risk Factors for Fall-related Injuries
Risk factors for fall-related injuries in older people are generally considered in terms of risk factors for falling, risk factors associated with the severity of the impact following the fall, and risks factors associated with low levels of bone mineral density—insofar as almost all fall-related injuries in older people involve broken bones. The risk factors associated with the latter two categories are generally related to aspects of the aging process and, as a consequence, are considered in more detail in chapter 51.
Analytical studies conducted in a variety of LMICs have tended to show that risk factors for fall-related injuries, especially hip fractures, are consistent with the risk factors identified in HICs. Those risk factors include low bone density; poor nutritional status and low body mass index; low calcium intake; comorbid conditions, such as hypertension and diabetes; poor performance in activities of daily living; low levels of engagement in physical activity; poor cognitive function; poor perceived health status; poor vision; environmental factors affecting balance or gait; family history of hip fracture; and alcohol consumption (Boonyaratavej and others 2001; Clark and others 1998; Jitapunkul, Yuktananandana, and Parkpian 2001).
Some studies have identified other factors that may be more relevant in the context of LMICs. For example, studies in Thailand suggest that factors associated with poor socioeconomic status may increase risk—for example, not having electricity in the house and living in Thai-style houses or huts (Jitapunkul, Yuktananandana, and Parkpian 2001).
The literature specifically identifying risk factors for falls in younger people in LMICs is sparse, but the information there is indicates that such falls usually occur in and around the home, with a significant proportion being associated with falls from heights, including rooftops and trees (Adesunkanmi, Oseni, and Badru 1999; Bangdiwala and Anzola-Perez 1990; Kozik and others 1999; Raja, Vohra, and Ahmed 2001). However, falls other than from heights predominate and are frequently related to engagement in vigorous levels of physical activity.
Risk Factors for Burn-related Injuries
Despite the focus of WHO's data on burn-related injuries sustained as a result of fires, a number of country-specific surveys conducted in medical facilities suggest that scalds from hot water may be equally important or more important causes of burn-related injuries (Chan and others 2002; Delgado and others 2002; Forjuoh, Guyer, and Smith 1995; Rossi and others 1998). However, in some countries, including China and particularly India, fire-related injuries clearly outweigh scald-related injuries (Ahuja and Bhattacharya 2002; Jie and Ren 1992).
Overall, women are at greater risk of fire-related burn injuries than are men; however, data from population-based and medical center surveys suggest that in some settings (excluding India), males may be at greater risk of burns than are females (Chan and others 2002; Zhu, Yang, and Meng 1988). In many studies, burn-related injuries account for a much higher proportion of injuries in young children compared with other age groups (Jie and Ren 1992; E. H. Liu and others 1998).
Rural location appears to be a consistent risk factor for burn-related injuries (Courtright, Haile, and Kohls 1993; Zhu, Yang and Meng 1988), as is the home (Delgado and others 2002; Forjuoh, Guyer, and Smith 1995; E. H. Liu and others 1998).
Investigators have undertaken case-control studies aimed at identifying risk and protective factors for burn-related injuries in Africa, Asia, and South America, and all focus on identifying risk factors for children. Environmental risk factors that have been identified include lack of a water supply, storage of a flammable substance in the home, cooking equipment in the kitchen within reach of children, and housing that is located in slums and congested areas. Persons with personal and socioeconomic risk factors included children who were not the first born, who had a pregnant mother, whose mother recently was dismissed from a job, who had recently moved, who had a pre-existing impairment, whose sibling died from a burn or had a history of burn, whose parents lacked alertness to burns, whose clothing was made of synthetic fabrics, whose parents were illiterate, and whose parents were of low economic status. Protective factors included the presence of a living room, better maternal education, and a history of previous injury among males who lived in good environmental conditions (Daisy and others 2001; Delgado and others 2002; Forjuoh and others 1995; Werneck and Reichenheim 1997).
Risk Factors for Drowning
Most drowning incidents in LMICs are not associated with recreation or leisure, as is commonly the case in HICs, but instead are associated with everyday activities near bodies of water, including rivers, wells, and buckets (Celis 1997; Hyder and others 2003; Kobusingye, Guwatudde, and Lett 2001).
As noted earlier, men account for a higher proportion of drowning incidents than women, and children age one to four and young people appear to be at greatest risk, with drowning accounting for a high proportion of injury-related deaths in those age groups (Celis 1997; Kibel and others 1990; Kozik and others 1999; Tan, Li, and Bu 1998). Some surveys also suggest that older people may be at particularly high risk (Tan, Li, and Bu 1998).
Descriptive surveys indicate that those living in rural areas are at greater risk than those living in urban areas (Kobusingye, Guwatudde, and Lett 2001), probably indicating greater exposure to unprotected water surfaces. A number of studies find that most adult drowning incidents appear to be associated with positive blood alcohol tests (Carlini-Cotrim and da Matta Chasin 2000; Celis 1997).
Case-control studies of drowning in young children have identified both sociodemographic risk factors and risk factors associated with proximity to bodies of water. Ahmed, Rahman, and van Ginneken's (1999) study in Bangladesh shows that the risk of drowning increased with the age of the mother and increased much more sharply the larger the number of children in the family. Celis's (1997) case-control study in Mexico finds that the risk of drowning associated with having a well at home was almost seven times that for children in homes without a well.
