Clinical and Health Affairs
Nonfatal Work-Related Traumatic Brain Injury in Minnesota, 1999-2008
By Chia Wei, M.S., Jon Roesler, M.S., and Mark Kinde, M.P.H.
■ The Centers for Disease Control and Prevention has identified traumatic brain injury (TBI) as a public health problem in the United States; it is notable that some variables of work-related TBI are different from those of non-work-related TBI. The Minnesota Department of Health has been conducting epidemiologic surveillance of cases of hospitalized TBI since 1993. Although most of the surveillance efforts have focused on all TBIs, the department does collect data on work-related TBIs and their associated outcomes. This article summarizes trends for nonfatal, work-related TBI cases over person, place, and time in Minnesota from 1999 to 2008. The greatest proportion of cases involved persons 35 to 44 years of age, and the most common causes were falls, motor vehicle traffic crashes, and being struck by objects. Most injuries occurred in the home, a location not routinely subjected to oversight for occupational safety concerns. The work-related TBI rate has been decreasing since 2004. This article also discusses the role of the physician in identifying and treating TBI.
Traumatic brain injury (TBI) is a significant public health concern. Broadly defined as brain injury from externally inflicted trauma, TBI often results in long-term or lifelong physical, cognitive, behavioral, and emotional changes.1 Each year, an estimated 2 million people in the United States sustain a TBI.2 Many of these individuals experience a mild injury and do not seek immediate medical treatment. However, others experience serious, acute consequences: Each year 52,000 people in this country die as a result of TBI, 275,000 are hospitalized, and 1.4 million are treated and released from an emergency department. The leading causes of TBI are falls (35.2%), motor vehicle crashes (17.3%), being struck by an object (16.5%), and assaults (10.0%).3
About one-third of adults hospitalized with a TBI still need help with daily activities one year after injury.4 Even persons with mild TBI can experience problems with short-term memory, concentration, learning new tasks, organization, judgment, and executive skills that can limit their ability to function independently.5 Patients with TBIs are often referred to as “the walking wounded.” Even though they appear physically “normal,” they may experience various levels of disability. Ideally, treatment of these patients involves a multidisciplinary approach, with the physician working in collaboration with the patient, family, psychologist, therapist, social worker, and staff from community-based organizations such as the local chapter of the brain injury association.
In Minnesota, more than 10,000 cases of hospital-treated TBI are reported annually. According to Minnesota Department of Health data, each year TBI results in more than 800 deaths, 4,300 nonfatal hospitalizations, and 6,500 nonfatal emergency department (ED) visits. Males are twice as likely as females to have a TBI, and the highest rates occur among individuals younger than one year of age, between 15 and 19 years of age, and older than 65 years of age.6
Work-related TBIs comprise only 4% to 5% of all reported TBIs, but these injuries can result in large claims and are the most serious of occupational injuries reported.7,8 Annegers et al. estimated that 5% of all TBI cases in Olmsted County, Minnesota, that occurred between 1935 and 1974 were work-related.9 A recent Canadian study found that the age and gender of the patient, mechanisms of injury, Injury Severity Score, length of hospital stay, and in-hospital death rate associated with work-related TBI were significantly different than those associated with non-work-related TBI.10
In order to get a more comprehensive understanding of work-related TBI trends in Minnesota, staff from the Minnesota Department of Health reviewed all reported nonfatal, work-related TBI cases. This article shares their findings, focusing on the distribution of occupational TBI by age, gender, and mechanism of injury, with discussion of the role of the physician in caring for patients with work-related TBIs.
Methods
When it established the mandate for a statewide registry of hospitalized TBI cases in 1991, the Minnesota Legislature defined TBI as sudden insult or damage to the brain or its coverings caused by an external physical force that may produce a diminished or altered state of consciousness and that results in 1) impairment of cognitive or mental abilities, 2) impaired physical functioning, or 3) a disturbance of behavioral or emotional functioning. These disabilities may be temporary or permanent and may result in partial or total loss of function.11 The Department of Health includes in the registry all reports of hospitalized cases and deaths in hospitals that are coded with one or more of the ICD-9-CM diagnostic codes established in Minnesota Rules, either as a principal or secondary diagnosis.12 Those include all of the TBI codes used by the Centers for Disease Control and Prevention (CDC),13 as well as other codes associated with TBI.
Additional criteria include whether the injured person was a Minnesota resident, whether the injury occurred in the state, and whether the injured person was transferred from a Minnesota emergency department to an out-of-state hospital. Out-of-state hospitals are asked to report cases in which the patient is a Minnesota resident or was injured in Minnesota. Excluded from the registry are patients who are seen in and discharged from an emergency department; admitted as outpatients for observation and then discharged; or admitted directly to a long-term care or rehabilitation facility. Data were reported to the Minnesota TBI Registry using the Minnesota Report of Injury.14
This analysis included all admissions to the Minnesota TBI Registry from 1999 to 2008 of persons who were at least 18 years old who were injured while working for income. The TBI rates were calculated from 1999 to 2008; denominators were the number of people employed in Minnesota, estimated from Minnesota Department of Employment and Economic Development statistics.15
“Working for income” was defined as working for wages or a salary, bonuses, or other types of income (eg, contract, barter, etc.).16 We used the primary ICD-9-CM external cause of injury code17 to analyze the causes of TBI. Patients who had multiple hospitalizations associated with an injury were only counted once in this study. Outcomes were assessed using the Glasgow Outcome Scale (GOS) at the time of discharge from the hospital.18 The GOS categories include “Good Recovery,” “Moderate Disability,” “Severe Disability,” and “Vegetative State.” Those expected to make a good recovery include persons with mild disability.
Results
A total of 1,722 eligible subjects were identified from the Minnesota TBI Registry and included in this analysis. The number of work-related TBI cases per year ranged from a high of 219 in 2000 to a low of 147 in 2002, representing 4.2% of all TBI cases during the 10-year period.
In order to better understand the trends associated with work-related TBI, we calculated the TBI rate per 100,000 persons employed in Minnesota. Figure 1 shows the TBI rate from 1999 to 2008, which peaked in 2000 and again in 2004. The injury rate decreased after 2004 and has been fairly steady, averaging 6.2 TBIs per 100,000 workers over the 10 years. The total days of inpatient hospitalization per year for all occupational TBI patients ranged from a high of 1,301 days in 2004 to a low of 710 days in 2002.
An analysis of TBI by month suggests that the number of reported cases peaks during the summer and decreases from December to April. Among all occupational TBI cases reported, the highest percentage of people injured while working for income were between the ages of 35 and 44 years (Table 1). The number of injuries was higher for males than females (1,306 and 416, respectively). (Denominators by gender of workers were not available to calculate rates.) Among males, the greatest proportion of occupational TBIs (23%) occurred among those 35 to 44 years of age. Among females, the greatest proportion (33%) occurred among those age 65 and older.
■ Causes
Based on the ICD-9-CM codes, the primary cause of work-related TBI was a fall (E880.0-E886.9, E888), accounting for the cause in 46% of all cases (N=785). Of those, 24% (n=188) involved people age 65 and older. Twenty-nine percent of cases (N=496) were caused by motor vehicle accidents (E810-819.9) and accidents involving other forms of transportation (E800-807.9, E820-E829.9) including motorcycles, bicycles, snowmobiles, and ATV/off-road vehicles. The number of TBIs associated with traffic-related accidents among young adults (those 18 to 24 years of age) was twice that of TBIs from falls in that age group (103 versus 52). The third leading cause of work-related TBI among people of all ages is being struck by a falling object (E916-E917.9). Our analysis found 135 cases (14%) in which a person was struck unintentionally by an object (eg, a tree, rock, or stone). Other causes of work-related TBI included assault (5%) and injury involving machinery (3%).
The top three places where occupational TBI occurs were homes not including farms, a place of industry or its premises, and streets and highways, respectively (Figure 2). Among those injuries occurring at home (N=532), a disproportionate number (28%) occurred among people aged 65 years and older. Twenty-five percent of those injured at industrial places were between 25 and 54 years of age.
■ Outcomes
Most patients (77%) who were hospitalized with a work-related TBI were discharged home (Table 2); 23% were discharged to an inpatient rehabilitation or skilled nursing facility. Of patients with a GOS score that indicated “Good Recovery,” 86% were discharged home for self-care. Of those with a GOS that indicated “Moderate Disability,” 77% were discharged to inpatient rehabilitation facilities.
Discussion
The public health approach to injury prevention is to collect surveillance data so that causes can be identified and interventions developed. This surveillance investigation gives us insight into occupational TBI trends between 1999 and 2008, the last 10 years for which data are available. This study’s strength is that it is population-based, using data from the statewide Minnesota TBI Registry.
The occupational TBI rate of 4.2% that we found was less than the 5% reported by Annegers et al. for Olmsted County decades earlier, perhaps reflecting a true decrease in the risk of occupational TBI. Furthermore, we observed that the rate decreased slightly between 1999 and 2008 (Figure 1). To some degree, this mirrors the decline seen nationally in overall work-related injury fatality rates, occupational TBI fatality rates, and in the overall rate of TBIs (both occupational and nonoccupational).19
In this investigation, we abstracted the external cause code from hospital data to determine the cause of TBI in Minnesota. The leading causes of occupational TBI in Minnesota are similar to those reported by the CDC, namely falls, motor vehicle crashes, being struck by an object, and assaults. Falling is an especially serious problem among persons 65 years of age and older. One study of fall-related injuries among the elderly, published in the American Journal of Epidemiology in 1990, found that approximately one-third of persons 65 years of age or older fall each year. Additionally, the authors noted that falling is a leading cause of death from injury for the elderly in the United States.20 Our findings are consistent with theirs, in that the leading cause of occupational TBI is falling, especially among persons 65 years of age and older. Further work is needed to describe the range of activities associated with these falls. Although fall prevention is an essential element of occupational safety and health programs, specifically targeting those programs to elders who work at home might make sense given our results. Wellness and fıtness classes aimed at increasing flexibility, job modifıcations to address chronic health problems such as visual or auditory defıcits, and occupational therapy to rehabilitate previous injuries and reduce the chances of reinjury also may reduce the risk of falls and fall-related TBIs in older workers.21
Our study had some notable limitations. For example, the Minnesota TBI Registry currently lacks data on a person’s occupation and the industry in which he or she works; these variables should be considered for inclusion in the registry. The activity of the patient at the time of injury is determined by the medical records coder; therefore, there is potential for a lack of precision in the category “working for income,” as it is ascertained from the narrative in the medical record instead of direct patient interview. As a result, hospital medical record staff and trauma registrars who report to the TBI Registry may under- or over-report the occupational TBI rate. This potential for bias remained even after we reviewed all of the injury descriptions and reclassifications. Thus, clear definitions and training should be provided to hospital medical records staff for coding “work for income” and “unpaid work.”
Although this analysis only included hospital data reported through the Minnesota TBI Registry, future efforts might link data from the Minnesota TBI Registry with Minnesota Department of Labor and Industry data in order to conduct a more comprehensive study of occupational TBI in Minnesota.
The Physician’s Role in Treating Patients with Work-Related TBI
Physicians need to be aware of the problem of work-related TBI and how it may manifest through patients complaining of frequent headaches, fatigue, ringing in the ears, blurred or double vision, depression, and other symptoms that have causes that are difficult to pinpoint. Given that these symptoms are not specific to TBI and are often associated with other chronic illnesses, it is important for physicians to be especially vigilant with older patients who are still working.
Many TBI survivors, particularly those who sustain mild injuries, do not receive formal medical follow-up. However, even those who have had rehabilitation or have reported contact with their primary care physician are often unable to recount any discussions about the return to work process. Given the invisibility of the consequences of their injury and the persistent symptoms affecting their ability to work, the lack of advice and guidance on the best time to resume working means that many may return before they are ready.
It is important for physicians to anticipate the rehabilitation needs of patients who have sustained a TBI.22 Successful rehabilitation of a TBI survivor requires the recognition of possible long-term sequelae, with appropriate referral for treatment of medical, cognitive, and behavioral problems in order to promote recovery and enhance reintegration into the community. Describing those at greatest risk for work-related TBI is the first step toward helping physicians identify individuals who may need further evaluation.
Conclusion
Work-related TBI is a public health problem that affects workers of all ages. It is costly, as even mild cases can cause problems with short-term memory, concentration, learning new tasks, organization, judgment, and executive skills—all of which can affect one’s productivity and ability to live independently.
Although the injuries themselves can be acute, the functional deficits from TBI may place a tremendous long-term burden on individuals, families, and the health care system. TBIs have been a leading cause of long-term disability in the United States, even before the current military conflicts, and are a leading contributor to increasing health care costs. Successful rehabilitation of a patient with a work-related TBI requires physicians to be able to recognize, refer, and treat the associated medical, cognitive, and behavioral problems in a timely way.23
Identifying those at greatest risk for occupational TBIs is the first step toward preventing them and for helping physicians recognize individuals who may need further evaluation and treatment. MM
Chia Wei is a graduate student intern, Jon Roesler is the epidemiologist supervisor, and Mark Kinde is the Injury and Violence Prevention Unit director with the Minnesota Department of Health, Health Promotion and Chronic Diseases Division, Center for Health Promotion.
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