Sleep, 17{1):84-93
© 1994 American Sleep Disorders Association and Sleep Research Society
Special Report
The Cost of Sleep-Related Accidents:
A Report for the National Commission
on Sleep Disorders Research
Damien Leger
Unite de Sommeil de I'H6tel-Dieu, Paris, France and
Sleep Research Center, Stanford University, Palo-Alto, California, U.S.A.
Summary: This report, prepared for the National Commission on Sleep Disorders Research, explores the economic
implications of sleepiness in relation to accidents. In Part One, I describe the frequency of accidents in the United
States and explain a method for estimating the economic cost of these of accidents. Accidents are the fourth leading
cause of mortality in the United States, and motor-vehicle accidents represent 51 % of total deaths caused by
accidents. The method used for calculating the cost of accidents is called "the human capital approach". It is based
on the principle that "one person produces a sum of output during his/her life-time, which can be approximated
by his/her earnings". It is necessary to understand that this estimate of human value is not intended to reduce
human beings to a sum of earnings during his/her lifetime. It does, however, serve as a useful indicator in making
decisions regarding public health policy for the country. The results of the total cost of accidents and the relative
costs for work-related, home-based and public accidents in 1988 are discussed. In Part Two, I explore the role
sleepiness plays in contributing to the total number of accidents. The difficulty of researching this subject is
compounded by the fact that reports of rates of accidents related to sleepiness differ significantly from author to
author. This is true both for drivers with sleep disorders and those without. We have calculated two different rates
for estimating the number of motor-vehicle accidents caused by sleepiness. The first is based on the percentage of
total accidents and fatal accidents that occur during the hours of maximum sleepiness 2:00 to 7:00 a.m. and 2:00
to 5:00 p.m., 41.6% of total and 36.1 % of fatal accidents, respectively. The second rate was simply the percentage
of total accidents that occur at night (54%). Other categories of accidents explored are work-related, home-based
and public accidents. If we assume that the rate of accidents due to sleepiness for falls and air transportation is the
same as that for motor-vehicle accidents, then we can apply this rate to falls and air transportation accidents in
cases of work-related, home-based and public accidents. Finally, I estimate the cost of accidents related to sleepiness
in each category, for accidents occurring in 1988. The total cost of accidents related to sleepiness in 1988 is estimated
to be between $43.15 billion and $56.02 billion. Key Words: Sleep-Accidents-Cost-Economics-HypersomniaSleepiness.
For the last fifty years, important medical discov- mains considerable, including not only the more puberies have resulted in a considerable decrease in the licized motor-vehicle accidents but also those occurmortality rate in the United States, especially among ring at work, at home and in public places. Faced with
the younger population. At the same time, the acci- the magnitude ofthese accidents, public authorities do
dental death rate continues to rise, and accidents are not have enough money to create an effective prevention policy. Because they face difficult choices related
the leading cause of youth mortality in America (1).
Accidents are by definition unforeseeable and, thus, to spending, public administrators have urged econdifficult to avoid. For several years, the prevention of omists to define the cost of accidents. This cost is only
accidents has been one of the main priorities of public an estimate of the real cost of accidents, which cannot,
health practitioners and public authorities around the of course, be reduced to a simple amount of money.
country. Nevertheless, the number of accidents re- But it is a useful tool in public health policy-making
as well as a means of helping the public understand
the economic disaster of accidents for individuals,
Accepted for publication August 1993.
families and the entire nation.
Address correspondence and reprint requests to Damien Leger,
The primary and obvious causes of accidents, such
M.D., M.P.H., Unite de Sommeil, Hotel Dieu de Paris, I place
Parvis Notre Dame, 75004 Paris, France.
as alcohol use (2), have a clearly documented place in
84
COST OF SLEEP-RELATED ACCIDENTS
85
disabling injuries when "they result in some degree of
permanent injury or when they render the injured person unable to effectively perform his/her regular duties
or activities for a full day beyond the day of injury".
The number of disabling injuries is not reported on a
national basis, but rather is ca1culated using approximations developed from special studies based on ratios
for disabling injuries to deaths.
Accidents do not affect the population uniformly.
Although they represent the fourth most common cause
of death in the country, they are the leading cause of
death for people between the ages of 1 and 37. The
greatest number of motor-vehicle fatalities in 1986 occurred among 21-year-olds. Twenty-five percent of the
licensed drivers in 1988 were in the 25-to 34-year age
group, but accounted for 27% of the drivers involved
in both fatal and total motor-vehicle accidents. Data
for 1986 show that 71 % of motor-vehicle deaths occurred among males and that 44% of the victims of
accident injuries and 39.3% of deaths resulting from
accidents occurred among people less than 27 years
old.
PART 1: THE COST OF ACCIDENTS
Ofthe estimated 164,200,000 drivers in 1988, about
85,200,000
were males and 79,000,000 were females.
The magnitude of accidents in the United States
Males are involved in more accidents than females. In
Accidents in the United States are of special concern 1988, 49,200 male and 14,800 female drivers were
in public health analysis, because for many years they involved in fatal accidents, and 22,500,000 male and
have been among the leading causes of mortality and 13,700,000 female drivers were involved in the total
disability in our country (2). Moreover, the population number of accidents (3). The difference is due at least
affected is far younger than that of other primary causes partially to differences in the amount of driving done
of mortality (3). Among the 2,126,342 deaths in the by the members of each sex and to differences in time,
United States in 1987, heart disease, cancer, stroke and place and circumstance of the driving.
accidents, in that order, were the four leading causes
When years of potential life before 65 are considered,
of mortality (4). Currently, the four primary causes of we begin to understand why accident-related injuries
accidental death are motor-vehicle accidents, falls, can be seen to rank first with respect to economic loss,
drowning, fire and bums.
accounting for about 2.3 million years lost in each 12Motor-vehicle accidents are by far the most frequent month period. Estimates by the National Center for
cause of death due to an accident. In 1988, deaths by Health Statistics for 1987 show further that accidents
motor-vehicle accidents represented 51 % of total deaths were responsible for 194,151,000 bed days and
caused by accidents. Of the remaining deaths, falls 621,167,000 restricted-activity days (8). This amounts
represent the second largest cause of accidental death, to 2.6 days of restricted activity per person, per year,
but affected an older age group. The total number of in the United States.
accident deaths in 1988 was approximately 96,000,
including 49,000 motor-vehicle accidents, 22,500 The method of calculation
home-based accidents, 18,000 public accidents and
Philosophers and economists have debated the value
10,600 work-related accidents. (Some deaths are included in more than one category of accident, which of human life for years (9). Most agree that placing a
explains the discrepancy between the total number of dollar value on human life is a senseless exercise. Obdeaths and its component parts. For example, 35% of viously, the value of every human life is greater than
any approximate market value based on loss of output
work-related deaths were vehicle accidents.)
Disabling injuries affected an estimated 9.1 million the individual would have produced during his/her
people in 1988, including 1.8 million motor-vehicle lifetime. During the last several years, however, the
accidents, 3.4 million home-based accidents, 2.3 mil- serious increase of health expenses and the economic
lion public accidents and 1.8 million work-related ac- necessity to make choices in public health policy have
cidents (3, 5-7). Accident-related injuries are called caused economists to reconsider this issue in terms of
public health policy and spending. They should not,
however, obscure the less visible ones, such as sleepiness, which appears to be an underrated cause of accidents. More attention has been focused in recent years
on the relationship between sleepiness and accidents.
Recent studies observe a link between sleep disorders
and motor-vehicle accidents. The incidence of sleepiness as a factor in accidents of any type among healthy
people remains, however, an unexplored field, and a
very small number of studies and related statistics are
available.
This article evaluates the economic implications of
sleepiness in relation to accidents. I will first survey
the frequency of accidents and discuss the economic
impact of accidents. The role of sleepiness with regard
to accidents will be explored before giving an estimate
of the cost of accidents related to sleepiness. With this
temporary estimate, we will have the means to foster
prevention, information improvement and research in
this still largely unexplored domain.
Sleep, Vol. 17, No.1, 1994
86
D. LEGER
"human life value". Economists now value human life
as the product or the result of the economic system of
public health, which includes not only medical activity
such as hospitalization, but also wellness care such as
accident prevention (10,11).
In the United States, the first studies concerning cost
of illness were performed by Dorothy Rice in 1966
(12-15). The methods were put into practice by several
workers, such as Paringer in 1975 (16), but the methodology initially used, "The Human Capital Approach", remains the same. The principle is that "one
person produces a sum of output during his/her lifetime, which could be approximated by his/her earning". Death or disability of this person is responsible
for the loss of his/her output, which can be estimated
by lost earnings.
Earnings data used in calculations of the cost of illness are based on actual earnings calculated on the
basis of age and sex by the Bureau of Labor Statistics
and are adjusted with wage supplements, such as social
insurance, private pensions and welfare funds (17). Included in earnings is an estimated value of household
work. The method employed to estimate household
work value is to obtain the market value of commercial
household services and to input household earnings to
all women under 65 who had ever been married, to all
married men and to women over 65 living with spouses, with an adjustment function for the number and
ages of dependent children.
Work productivity varies among age and sex groups.
The estimate must take into account experience, age
and sex, and studies generally use the work experience
rate defined by the Bureau of Labor Statistics.
For the cost of lost wages, actual losses are used for non-fatal
injuries, and the present value of all future earnings lost are
used for fatalities and permanent disabilities. The cost ofmedical expenses includes doctor fees, hospital charges, cost of
machinery, am bulance and emergency services, and all medical
services in the present and future required due to disability.
The cost of insurance administration represents the costs to
insurance companies, that is, the difference between premiums
paid to insurance companies and claims paid out by them. It
is, however, a part of the total accident-related cost. Not included are administrative costs of health maintenance organizations and property damage claims for home-based and public
accidents. The cost of property damages in motor-vehicle accidents includes the value of property damage to vehicles. The
cost of fire loss includes loss from building fires of$7.2 billion
and from non-building fires of$I.2 billion. The cost of indirect
losses from work-related accidents includes the cost of time
lost by non-injured workers, such as time spent to fill out
accident reports and give first aid to injured workers, and time
lost due to production slowdowns. This loss is estimated to be
an important as the direct cost of accidents, which is $22.0
billion.
Economists now generally agree that human value
can be calculated as the direct and indirect costs resulting from an individual's premature death, for himself/herself, his/her family, and his/her country
Sleep, Vol. 17, No.1, 1994
(11,12,14-16). It is necessary to understand that this
estimate of human value is not intended to reduce
human beings to a sum of earnings during his/her lifetime. It does, however, serve as a useful indicator in
making decisions regarding public health policy for the
country, for example when predicting the impact of
new medical technology or improving the safety of a
dangerous highway.
The cost of illness in the United States: Definition
The cost of each illness can be broken down into
direct and indirect costs (12,13). The direct costs represent all resources that could be distributed to other
sectors of the economy in the case of absence of illness
(doctor fees, hospitalization costs, treatment, etc.). The
indirect cost is the cost of lost productivity due to
disability or premature fatality, which was the result
of an illness or accident. As a component of these costs,
disability costs include loss of work plus the value of
loss of household tasks when a person becomes disabled or institutionalized after an illness or accident.
In fact, some of these costs, such as that of housekeeping, do not have a direct impact on the gross national product. They must, however, be considered as
a component of the cost.
The economists of the National Highway Traffic
Safety Administration use the cost of accidents to help
their administration make sound choices concerning
safety investment in highways (18,19). They also employ the Human Capital Approach to calculate the
economic value of an accident. The calculation is based
on the loss of gross production and not on the net
production, which is only the percentage of earnings
that one individual does not consume by himself/herself. As with illness, the costs of an accident can be
broken down into direct and indirect costs. Direct costs
include monies to repair materials and rehabilitate
people, such as medical and legal fees and property
damage repair costs. Indirect costs represent the loss
of production and welfare for the individual and the
nation due to premature death or disability. The indirect cost of accidents includes costs of administration
and human capital (this represents lost productivity
for injuries or a fatality and is adjusted for individuals'
willingness to pay to reduce their risk of death or injury).
Recent studies performed by the National Highway
Traffic Safety Administration (20-23) calculate the costs
divided into seven categories of severity, called the
Maximum Abbreviated Injury Scale (MAIS) categories. The category indicates property damage only,
with no bodily injury. Categories 1-5 represent the
range from the least to the most severe nonfatal injury,
and category 6 represents fatalities (Table 1). These
°
COST OF SLEEP-RELATED ACCIDENTS
TABLE 1.
Type of
cost
Costs by MAIS categories (J 980 dollars)
TABLE 3.
87
Certain costs of accidents by class (billions of
dollars)a
Category
0
2
3
4
5
6
716 1,601 3,442 8,098 18,467 138,684 18,294
Direct
Indirect 1,321
690 1,165 2,217 32,564 122,897 724,227
848 2,291 4,607 10,306 51,031 261,581 742,521
Total
Source: J. B. Rollins and W. C. McFarland 1986 (24).
costs are expressed on a per-victim or per-vehicle basis.
A more recent analysis (24) shows that it would be
more convenient to use cost-benefit analysis and express it on a per-accident basis, calculated by severity
(Table 2).
These estimates are obviously lower than real economic losses due to traffic accidents, inasmuch as they
include only economic loss related to a specific activity,
not the time lost by other people directly or indirectly
affected by the accident. For example, it has been calculated that for a fatality, the increased transportation
time for other people is about 475 hours per accident.
Other inestimable factors are the cost of suffering and
the far-reaching social implications caused by loss of
affection and friendship. These effects cannot be measured economically; they have, however, a very strong
impact on society's production potential (25).
Results for 1988
Total cost of accidents
According to the National Safety Council, the cost
to the nation for accidents in 1988 was at least $143.4
billion (6). This figure includes the costs of $70.2 billion for motor-vehicle accidents, $47.1 billion for workrelated accidents, $17.4 billion for home-based accidents and $10.9 billion for public accidents. The total
cost is broken down in Table 3.
TABLE 2. Net costs of incapacitating accidents, nonincapacitating accidents, and possible injuries in fatal and injury
accidents (1980 dollars)
Cost per injury (dollars)
Accident severity
and type of cost
Fatal
Direct
Indirect
Total
Injury
Direct
Indirect
Total
NonIncapacitating incapacitating
Possible
injury
Type of cost
Total
Wage loss
Medical expenses
Insurance
Fire loss
Motor vehicle
property damage
Indirect work loss
Total
37.1
23.6
38.7
8.4
Motor
vehicle
20.3
5.0
21.3
Work
7.9
8.1
6.0
3.1
Public
(nonmotor
Home vehicle)
5.8
6.7
0.8
4.1
4.7
4.4
0.6
1.2
23.6
23.6
22.0
22.0
70.2
47.1
17.4
143.4
10.9
Source: National Safety Council estimates. Accidents Facts 1989
Edition (3).
a Duplications between work-related and motor-vehicle accidents
and home-based and motor-vehicle accidents are eliminated in the
totals.
Cost of motor-vehicle accidents
The estimate of $70.2 billion in 1988 (24) can be
broken down as follows:
Wage loss costs
Medical expenses
Insurance administration
Property damage from motor-vehicle
accidents
$20.3 billion
$5.0 billion
$21.3 billion
$23.6 billion
Not included in this total are the costs to public agencies, such as police departments, fire departments and
courts, indirect losses to employers for off-the-job accidents to employees, the value of cargo losses in commercial vehicles and damages awarded in excess of
direct loss.
The National Safety Council has compiled estimates
of the per-case cost of motor vehicle-related deaths
and injuries and property damage, as follows:
Per death
Per nonfatal disabling injury
Per incapacitating injury
Per nonincapacitating evident injury
Per possible injury
Per property-damage accident
$290,000
$13,100
$30,600
$7,500
$1,000
$1,700
Cost of work-related accidents
20,112
24,203
44,315
4,304
4,086
8,389
1,839
1,876
3,715
In the estimate of $47.1 billion for work-related accidents in 1988 (25) are included direct costs of
6,783
7,612
14,395
2,213
1,775
3,988
972
751
1,723
Wage loss
Medical expenses
Insurance administration
Fire loss
Source: J. B. Rollins and W. C. McFarland 1986 (24).
$7.9
$8.1
$6.0
$3.1
billion
billion
billion
billion
Sleep, Vol. 17, No.1, 1994
88
D. LEGER
and an indirect cost of$22.0 billion, which is generally
assumed to be equal to the direct cost. It does not
include, however, the value of property damage, other
than for fire loss.
On a per-accident basis, the following costs are obtained:
These estimates are based mainly on the results of
recent reports published on the relationship of accidents and sleepiness (29-31).
The circadian cycle of sleepiness
Several studies have shown a tendency for a circadian rhythm of sleep during both daytime and night$410 time (32-34). There is a peak of sleep tendency from
around 2:00 to 7:00 a.m. and a smaller one from 2:00
$550,000 to 5:00 p.m. (30,35-39). Sleep tendency is also increased by sleep deprivation and sleep disruption. The
$16,800 effects of sleep loss are cumulative; sleepiness increases
progressively with the sleep debt (40-48).
Other studies have revealed the circadian distribuTime lost because of work-related injuries
tion of performance errors during the nighttime. A
Swedish study (49) shows that two peaks of maximum
In the United States, the total time lost due to work- error occur during the 24-hour cycle: one is between
based injuries registered in 1988 is estimated to be 2:00 and 4:00 a.m. and the other, less pronounced one,
75,000,000 days, with 35,000,000 days directly lost is between 2:00 and 4:00 p.m. Reaction time and perdue to the accident itself and 40,000,000 days lost formance are also considerably reduced during the night
within the year due to work-related disease following (36,37,50,51).
the accident. Projected losses into the future for acciDespite this physiological evidence, very few studies
dents occurring in 1988 are approximately 100,000,000 have been performed to show the specific role of sleepdays. Fatalities are included in this figure and represent iness in accidents, especially in work-related accidents.
an average loss of 150 days per case. An estimate of Most studies to this point concern motor-vehicle acthe cost of permanent impairment is also included. cidents.
Not included is time lost by persons with nondisabling
injuries and the value of the time of other persons
Statistics regarding motor-vehicle accidents and
directly or indirectly involved in the accident (3).
In 1988, off-the-job accidents totaled about sleepiness
60,000,000 days of production time lost in the first
A U.S. Department of Transportation report on
year following an accident, compared with 35,000,000 transportation-related sleep research cites several studdays lost by workers injured on the job. Production ies concerning the role of sleepiness in transportation.
time lost in years subsequent to the accident is esti- According to these studies, drivers without sleep dismated to be 290,000,000 days. Off-the-job-accidents orders report-at a rate of less than 20%- "sleeping
to workers cost the nation at least $44.0 billion in 1988 episodes" while driving. Also, the studies indicate that
(3). When considering these estimates, the remarkable motor-vehicle accidents are directly related to sleepiimpact of accidents on the economy is seen clearly.
ness in 1-10% of cases (31,51,52).
Cost of one work-related accident per
worker
Cost of one work-related accident with
death
Cost of one work-related accident with
disabling injury
Another interesting study performed by the National
Highway
Transportation Safety Administration
PART 2: ACCIDENTS RELATED TO
through
the
Advance Datafile (CARfile) (31) concerns
SLEEP DISORDERS
3.1 million crashes in five states where sleep-related
For many years, sleepiness as a cause of accidents crashes are registered separately. 1.4 percent of crashes
was largely unstudied. In recent years, however, several and 1.75% of motor-vehicle fatalities were related to
persons have studied the incidence of falling asleep at sleepiness; 76% of these were single-vehicle crashes.
the wheel as a factor in many motor-vehicle accidents. Another CARfile study shows that 4% of the 6.6 milThe role of sleepiness and sleep disorders appears to lion driver-error citations reported could be related to
be underestimated in comparison with the classic caus- sleepiness or inattention.
These -estimates, however, seem to be very low, and
es of accidents, such as alcohol and drug abuse, which
could also be associated with sleepiness (26-28).
sleepiness is probably underreported for many reasons.
In the sections that follow, we have not attempted· The question of fatigue is not often asked of injured
to prove the relationship between accidents and sleep- people. Sometimes those involved do not wish to ininess, but rather provide estimates concerning the per- form officials or even their friends and relatives that
centage of accidents that could be related to sleepiness. they were asleep at the wheel, because this implies
Sleep, Vol. 17, No.1, 1994
COST OF SLEEP-RELATED ACCIDENTS
89
could be related to inattention and tiredness. A general
survey from the State of Arizona reports that 42-49%
of commercial vehicle accidents in that state were due
to driver sleepiness or inattention (Arizona Department of Public Safety, 1988). Sometimes the drivers
themselves are not aware that they are sleepy, as suggested by several studies showing that train engineers
can operate a train for several minutes after falling
asleep
(58,59).
Sleepiness and accidents: The reality
To summarize, an estimated minimum percentage
The following facts suggest that the number of sleep- of total and fatal accidents related to sleepiness is inrelated accidents is greater than that reported in the dicated by the CARfile study estimate (31). This study
is the most extensive to date and its results show that
statistics.
1.4% of total accidents and 1.75% of fatalities are directly
related to sleepiness. To obtain the lowest estiAccidents related to sleep disorders
mation of the number of accidents caused by drowsWhen people with sleep disorders are asked about iness, it would seem more appropriate to use the number
driving and accidents, their answers indicate that the of accidents that occur during the hours of maximum
frequency with which they fall asleep while driving drowsiness (41.6% of total and 36.1% of fatal accicould be between 30 and 93%, depending on their dents). This probably would give an overestimation,
pathology (53-57). For sleep apnea patients, accident as not all accidents are caused solely by drowsiness;
rates of 31-93% have been reported. For narcoleptics, however, not enough attention is paid to drowsinessstudies have reported that 40-48% of subjects inter- related accidents occurring during other periods, thereviewed had fallen asleep at the wheel and 25% had had by balancing out the difference.
accidents related to their sleepiness. Twenty-four perThe proportion of accidents occurring at night (54%)
cent of individuals who suffer repeated episodes of will be taken as the upper limit for our estimates. Thus
falling asleep at the wheel do so at least once a week. the estimated interval is between the lower limit, 36.1 %
The Stanford Sleep Disorders Clinic statistics show of fatal and 41.6% of total accidents, and the upper
that 15-45% of all patients suffering from sleep apneas, limit, 54% of total accidents. These figures will be used
12-30% suffering from narcolepsy, and 2-8% suffering in later sections of this paper to compute the costs of
from insomnia, have had at least one accident related sleep-related accidents.
to sleepiness. These patients know that they have a
problem with sleepiness and consequently do not hes- Work-related accidents
itate to relate their accidents. These results cannot be
The estimates of accidents occurring at work that
compared with those gathered from ordinary drivers.
However, a great number of Americans do not know might reasonably be related to sleepiness are those rethat they suffer from sleep disorders and for them it is sulting from motor-vehicle accidents (35.0% of total
more difficult to admit to falling asleep at the wheel. work-related accidents), falls (12.6%) and water and
air transportation accidents (4.8%), combination for a
total of 52.5% of all work-related accidents in 1988.
Motor-vehicle accidents and sleepiness
The other 47.5% of work-related accidents was caused
Analysis of deaths attributed to motor-vehicle ac- by drowning, electrocution, fires and the like, which
cidents in 1988 showed that more than 54% had oc- are not assumed to be attributable to sleepiness.
curred at night (3). The accidents occurring during the
Aspects of work-based accidents that may be related
hours of maximum sleepiness (2:00 to 7:00 a.m. and to sleepiness are discussed in more detail below.
Shift work. The incidence of shift work in the United
2:00 to 5:00 p.m), which comprises 33% of the 24hour day, accounted for. 36.1 % of the fatal accidents States certainly has an underrated impact on the magand 41.6% of total accidents for 1988. Whatever the nitude of work-related accidents. About 25% of workstated causes found to explain these accidents, alcohol, ing Americans are engaged in shift work and 6% of
lack of visibility, bad weather, etc., it is obvious that night-shift work. The transportation industry is the
sleepiness enters as a co-factor in the great majority of nation's third largest employer of shift workers, behind
these accidents. These statistics confirm that among health care and data processing (60).
A number of studies have been performed on nightmotor-vehicle accidents occurring during the night,
most are related to sleepiness. Moreover, most of the shift workers. These studies show that sleepiness innighttime accidents are single-vehicle accidents, which creases during the shift and reaches a pronounced peak
admission of responsibility for the accident. Occasionally drivers do not know themselves that they were
asleep. Sleepiness is often ignored because the accident
can be attributed to other causes, such as alcohol, bad
weather or impairment due to drug use, and because
it is not as easy to determine fatigue as it is to ascertain
the use of alcohol or drugs.
Sleep. Vol. 17. No.1. 1994
90
D. LEGER
during the second half of the night (61,62). It is common for night-shift workers to fall asleep during the
night (63). The symptoms preceding these episodes of
sleep invariably are sleepiness, fatigue and the struggle
to stay awake. Symptoms increase during the night,
and are frequently followed by unavoidable naps (6466). This sleepiness is present for 75-90% of nightshift workers as compared to 0.3-6% of daytime workers. (67-69).
Chronic sleep disorders affect 60-80% of all shift
workers (70-72) and night-shift workers regularly experience a shortened daytime sleep. Sleepiness affects
75-90% of night-shift workers every night (62,73,74).
It has been proven that a great number of shift workers
fall asleep during the night shift (58,59,63).
Shift workers also have many family- and healthrelated problems and experience two times more motor-vehicle accidents than non-shift workers. They are
also two to five times more likely to be addicted to
alcohol or drugs.
On-the-job motor vehicle accidents. Motor-vehicle
accidents represented 35% of the 47,900 deaths and
4,600,000 disabling injuries occurring at work in 1988.
For these accidents, we will assume that the previously
estimated percentage of total motor-vehicle accidents
attributed to sleepiness (41.6% of total and 36.1 % of
fatal accidents occurring during the two peaks of sleepiness or 54% ofthe total percentage of night accidents)
can also be applied to on-the-job vehicle accidents in
calculating costs. Furthermore, these figures will be
extended to other types of transportation accidents,
which represent 4.8% of the work-related accidents in
1988.
Falls during work. Although there are no data collected on the nature and timing of falls, it is obvious
that most falls occur due to inattention. We assume
that for every such accident the pattern of error is the
same as that occurring in the more frequently studied
motor-vehicle incidents, and this leads to the same
result. Obviously, and fortunately, only a small percentage of errors result in accidents. This percentage
is, however, extremely dependent on the degree of
sleepiness or inattention. Based on this observation
non-motor-vehicle accidents, such as falls, can be
treated in the same manner as motor-vehicle accidents.
Thus, it is possible to attribute the same total percentage of work-related accidents as estimated above
(54%) to work-related falls resulting from inattention
or sleepiness in calculating the cost of accidents related
to sleepiness.
Home-based and public accidents
The only home-based and public accidents that could
be related to sleepiness are falls, inasmuch as other
Sleep, Vol. 17, No.1, 1994
types of accidents, such as drownings and fire-related
injuries are likely to be attributable to other causes. In
1988, 6,500 (28.9%) of home-based accidents and 4, 100
(22.8%) of public accidents were deaths from falls. Applying these percentages to the total disabling injuries
at home and in public places, it can be concluded that
982,000 home-based injuries and 524,400 public injuries result from falls. As mentioned above (see Falls
during work), falls resulting in death or disability stem
mainly from error or inattention in a dangerous situation. It is assumed that this inattention could be attributed to sleepiness at the same rates estimated for
vehicular accidents.
Transportation accidents represent 2,200 of the total
18,000 deaths by public accident and 12.2% of the
2,300,000 disabling injuries. To evaluate the cost of
sleep-related accidents, we make the same assumptions
concerning these vehicle accidents as are made for general motor-vehicle accidents.
PART 3: ESTIMATE OF THE COST OF
ACCIDENTS IN RELATION TO
SLEEP DISORDERS
If the estimates concerning the percentage of accidents from the different classes attributed to sleep disorders are correct, the costs can be calculated as follows.
Cost of motor-vehicle accidents caused by sleepiness
Motor-vehicle accidents in 1988 represent 49,000
deaths and 1,800,000 disabling injuries producing a
total cost of $70.2 billion. According to the first estimate attributed to sleepiness (those vehicle accidents
occurring during the maximum hours of sleepiness),
41.6% of total accidents = 769,184 disabling injuries
and 36.1 % offatalities = 17,689 deaths combining for
a total cost of $29.2 billion (41.6% of the total). According to the second estimate, 54% of the total vehicle
accidents occurring at night represent 998,460 disabling injuries, at a total cost of $37.9 billion.
Cost of work-related accidents caused by sleepiness
In 1988 10,600 deaths and 1,800,000 disabling injuries were attributed to work-related accidents, giving
a total cost of $47.1 billion. Using calculations described in the previous section, it is estimated that
52.5% of all work-related accidents may potentially be
related to sleepiness. This gives us an estimate of 5,565
fatalities and 945,000 disabling injuries, creating a cost
of $24.7 billion. The first estimate of the cost related
to sleepiness includes 41.6% of total accidents, resulting in 393,120 disabling injuries, and 36.1 % of fatal
COST OF SLEEP-RELATED ACCIDENTS
91
accidents, resulting in 2,009 deaths, for a total cost of
$10.27 billion (4l.6% ofthe total). The second estimate
is 54% of the total accidents or 513,324 disabling injuries, at a total cost of $13.34 billion.
1,907,072 disabling injuries and 24,318 fatalities, creating a cost of $43.15 billion in 1988. The second
estimate involves 2,474,430 disabling injuries, at a total cost of $56.02 billion.
Cost of home-based and public accidents caused by
sleepiness
Conclusions
Home-based accidents
Falls represent 6,500 of the 22,500 home-based accidental deaths or 28.9% (982,600) of the 3,400,000
home-based disabling injuries. The cost offalls equals
28.9% of the cost of home-based accidents ($17.4 billion) or $5.03 billion. The first estimate of the cost
related to sleepiness includes 4l.6% of total accidents,
resulting in 408,762 disabling injuries, and 36.1 % of
fatal accidents, resulting in 2,346 fatalities, for a cost
of $2.09 billion (4l.6% of total). The second estimate
is 54% of the total accidents or 530,604 disabling injuries, at a total cost of $2.72 billion.
Public accidents
Falls. Falls account for 4,100 deaths or 22.8%
(524,400) ofthe 2,300,000 disabling injuries that happen in public places. This represents $2.5 billion of the
$10.9 billion cost of accidents in public places. The
first estimate of the cost related to sleepiness includes
41.6% of total accidents, resulting in 218,150 disabling
injuries, and 36.1 % offatal accidents, resulting in 1,480
fatalities, for a cost of $l.04 billion (4l.6% of total).
The second estimate is 54% of the total accidents or
283,176 disabling injuries, at a total cost of $l.34 billion.
Transportation-related accidents within the category
of public accidents. Transportation accidents account
for 2,200 deaths and 12.2% (281,111) of about
2,300,000 disabling injuries occurring in public places.
This represents $2.33 billion of the $10.9 billion cost
of accidents in public places. The first estimate of the
cost related to sleepiness includes 41.6% of total accidents, resulting in 117,856 disabling injuries, and
36.1 % of fatal accidents, resulting in 794 fatalities, for
a cost of $0.55 billion (4l.6% of total). The second
estimate is 54% of the total accidents or 151,800 disabling injuries, at a total cost of $0.72 billion.
Total estimated cost of accidents
related to sleepiness
The total estimated cost of each estimate is based
on the sum of all component costs. Thus, the first
estimate of the cost related to sleepiness includes
1. The total economic cost of sleepiness related to
accidents, including motor-vehicle, work-related,
home-based, and public accidents, is estimated to have
been between 43 and 56 billion dollars in 1988.
2. Sleepiness seems to be a very underrated factor
in accidents, not only as a primary cause but also as a
co-factor related to other well-known factors, such as
alcohol or drug abuse and hazardous driving conditions.
3. Every American could one day be affected by an
accident caused by sleepiness. Two Gallup polls have
indicated that 75% of the general population in America (about 180 million people) have trouble sleeping
and 20% (about 50 million) have had a serious problem
with insomnia. Those men and women are part of the
164 million licensed drivers in the United States.
4. The magnitude of the economic impact is compounded by the young population affected by accidents, especially fatal accidents. These young Americans are hit during their peak of productivity, with
adverse effects on themselves, their families and the
nation. At the same time, it is known that young Americans often have poor sleep habits, resulting in daytime
sleepiness.
5. More than 50% of total accidents occur at night.
Less than 10% of patients with insomnia are identified
by the physician at the primary care level. About 6%
of American workers are employed in night-shift work
and 25% in shift work. When considered together, these
data suggest that a large part of the economic impact
of sleep disorders could be avoided by good information about the potential dangers of such situations.
6. The data available to document the social and
economic impact of sleepiness on accidents are largely
inadequate. Estimates should be improved by studies
and epidemiological works.
7. The social and economic impact of accidents related to sleepiness certainly supersede any estimate
based on the percentage of accidents occurring during
the major period of sleepiness. Factors not considered
in the cost-related consequences of sleepiness are industrial catastrophes in which sleepiness may be involved (30,75), the time lost by people not injured but
directly concerned by the accidents (e.g. families, relatives, traffic and industrial slowdowns) and the consequences of near accidents, which are probably 5 or
6 times more numerous.
Sleep. Vol. 17, No.1, 1994
D. LEGER
92
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