Fatigue & Driving: Who is At Risk A Laboratory and Field Perspective

Christopher L. Drake, PhD

Wake Up Michigan!September 20, 2007

Christopher Drake, PhD, D.ABSMChristopher Drake, PhD, D.ABSMSenior Bioscientific StaffSenior Bioscientific StaffHenry Ford Hospital Sleep CenterHenry Ford Hospital Sleep CenterAssistant ProfessorAssistant ProfessorWayne State UniversityWayne State UniversityCollege of MedicineCollege of Medicine

The Sleep FactsThe Sleep Facts

Adult sleep need is 8.2 per 24 hours, with little variability (homeostatic “set point”)

Impairment in performance occurs with as little as 2 hours less per night.

Sleep debt from restricting sleep to 5-6 hours a night accumulates with time, and awareness of sleepiness declines.

Circadian timing has a major impact on performance, and is not addressed in many service guidelines (i.e., truckers, aviation)

Consequences of Sleep Loss

Behavioral/MoodSleepinessPsychomotor ImpairmentAccidentsDecreased Work Productivity Reduced Quality of LifeDeficits in Learning/MemoryStimulant SeekingAlcohol InteractionMood Effects Lack of Awareness

PhysiologicHypoxemiaInsulin Resistance Sympathetic ActivityBlunted Arousal Response

(hypoxemia, C02, EEG)

The Scope of the Problem

Estimates by US National Highway Traffic Safety Administration 1-4% of highway crashes caused by sleepiness Principal cause in 100,000 police-reported crashes 4% of all fatal accidents caused by sleepiness

A drowsy driver operating a motor vehicle at 60 mph in the right-hand lane (12’ wide) of a divided highway with a breakdown lane (11’ wide) can drift off the road at ~4° angle in less than 4 seconds

National Highway Traffic Safety Administration. 2002. National Highway Traffic Safety Administration. 2002. Available at: http://www.nhtsa.dot.gov.Available at: http://www.nhtsa.dot.gov.National Highway Traffic Safety Administration. 2002. National Highway Traffic Safety Administration. 2002. Available at: http://www.nhtsa.dot.gov.Available at: http://www.nhtsa.dot.gov.

Causes of Excessive Daytime SleepinessCauses of Excessive Daytime Sleepiness

• Reduced Sleep at NightReduced Sleep LengthReduced Sleep Continuity

• Circadian Phase

• CNS acting Drugs

• CNS Diseases

Reported Total Sleep Time (Ages 18-23)

6

7

8

1910 2003

Rep

ort

ed T

ota

l S

leep

Tim

e(h

rs/n

igh

t)

Survey Year

Terman & Hocking,

1913

Roth, et al,2003 (unpubl)

180180 240240 300300 360360 420420 480480 540540 600600 660660

Nightly Total Sleep Time (min)Nightly Total Sleep Time (min)

2%2%

4%4%

6%6%

8%8%

10%10%

Pe

rce

nt

Pe

rce

nt

6.8 hrs/nt6.8 hrs/nt

Mean Reported Nightly Total Sleep Time (2-weeks)Mean Reported Nightly Total Sleep Time (2-weeks)

15%15%

N=3283N=3283

Drake et al., 2002Drake et al., 2002

Sleepiness accumulates

over time

3h TIB

5h TIB

7h TIB9h TIB

4h TIB

6h TIB

8h TIB

A. Van Dongen HPA et al. Sleep. 2003;26:117-126.

B. Belenky G et al. J. Sleep Res. 2003;12:1-12.

Review: Dinges DF et al. Chronic Sleep Restriction. In: Kryger MH et al. (Ed.) Principles and Practice of Sleep Medicine W.B. Saunders, Philadelphia, PA, 2005, 67-76.

Experiments on chronic restriction of sleep from 1-2 weeks reveal cumulative increases in lapse rates in a sleep-dose response manner.

Vehicle Accident Data

Fatigue-Related Accidents

Time of DayMidnight 6 AM Noon 6 PM Midnight

International Data N = 6052

1200

1100

1000

900

800

700

600

500

400

300

200

100

Mitler MM, et al. Sleep. 1988.

No

. of

Acc

iden

ts

Midnight 6 AM Noon 6 PM Midnight

Overlay of Vehicle Accident Data, Performance Errors, and Circadian Rhythms

Shift workers

Patients with chronic psychiatric disease

Patients with chronic medical disease

Transportation workers

Medical staff

Young males

Populations at High Risk Of Sleepiness/Fatigue Related Accidents

Relationship between sleepiness & Accidents

Approximately 27% of drivers who have lost consciousness behind the wheel fell asleep as opposed to fainting, seizure, heart attack, etc.

Importantly, this 27% accounted for 83% of the fatalities.

Parsons, 1986 QJM.

0

2

4

6

8

0

1

2

3

4

Extended Work Shifts and Risk for Motor Vehicle Accidents Among Interns

0 Extended Shifts

1-4 Extended Shifts

>4 Extended Shifts

Od

ds

Rat

io (

95%

CI)

Od

ds

Rat

io (

95%

CI)

Nonextended Shifts (<24 h)

Extended Shifts (≥24 h)

1.0 1.0 1.0 1.02.3

5.9

1.8

2.4

1.7

3.7

Crashes Near-missIncidents Nod Off or Fall Asleep

Driving Stopped

*P <0.05 vs nonextended shifts or no extended shifts.Barger LK, et al. N Engl J Med. 2005;352:125-134.

*

*

*

*

*

*

Obstructive Sleep Apnea

Courtesy of Dr. Jonathan R.L. Schwartz. University of Oklahoma Health Sciences Center.University of Oklahoma Health Sciences Center.

Excessive Sleepiness and DrivingCollisions, Costs and Fatalities

Consequences of OSAS 810K collisions $15.9 billion in collision

costs 1,400 fatalities

Estimated cost-savings with CPAP treatment Prevent >500K collisions Reduce collision costs by

$11.1 billion Save nearly 1,000 lives

Meta-Analysis of 6 studies:Risk of MVC is greater in drivers with

OSAS than drivers without OSAS

CPAP, continuous positive airway pressure; MVC, motor-vehicle collision; OSAS, obstructive sleep apnea syndrome.Sassani A, et al. Sleep. 2004;27(3):453-458.

0.5 1 2 5 10

Odds Ratio

Findley, 1998

Barbe, 1998

Teran-Santos, 1999

Hortsmann, 2000

Lioberes, 2000

George, 2001

Fixed Combined

Findley LJ et al. N Engl J Med 1989.

Car Crashes in Sleep Apnea Patients

0.3

0.4

0.5

0.6

0All Drivers

(N=3.7)

Cra

shes

/Dri

ver/

5-Y

ear

(Mil

lio

ns)

0.1

0.2

Mild Apnea(N=16)

Moderate Apnea(N=17)

Severe Apnea(N=13)

 

Epidemiology

Established OSA=5%

95% of patients with

clinically significant and treatable OSA

remain undiagnosed

*Approximate breath ethanol concentration (BrEC) at peak; †Above 0.05% for legal intoxication in many states. N=32 healthy subjects without prior sleep deprivation and with 85% sleep efficiency. Sleep loss group (n=12) was tested in all 4 conditions, with 3 to 7 days of recovery time between tests, and compared with ethanol group (n=20).Roehrs T, et al. Sleep. 2003;26:981-985.

BrE

C, %

*

Sleep time (hours in bed)

0.045

0.095 0.102

0.190

0.00

0.05

0.10

0.15

0.20

6 4 2 0

Le

ga

l Into

xic

atio

n†

Hours of Sleep and Equivalent Blood Alcohol Level for Sedative Effects

Sleep deprivation is often combined with other impairment (e.g., alcohol) and these combined effects can be devastating to driver performance

Combined Effects

Driving Simulator Data

Roehrs, et al. Alcohol Clin Exp Res 1994;18:154.

8 HR 4 HRTime in Bed (Mean [SEM])

40

35

30

25

20

15

10

5

0

Placebo

Off

-Ro

ad D

evia

tio

ns

Sleep-Alcohol Interaction(Driving Simulator—AM)

Ethanol

Sleep Deprivation Is Associated With Decreased Cortical Activity

FDG, fluorodeoxyglucose; PET, positron emission tomography.Thomas M et al. J Sleep Res. 2000;9:335.

18FDG PET Study of Healthy, Sleep-Deprived Adults, Showing Decreased Metabolism in the Thalamus, Prefrontal Cortex, and Inferior Parietal Cortex

Prefontalcortex

Inferior parietalcortex

Occipitalcortex

Thalamus

Detection of “Microsleeps” in Medical Detection of “Microsleeps” in Medical ResidentsResidents

ReportedReportedStateState

Physiologic StatePhysiologic State

49%49%

51%51%

88%88%

12%12%

Sleep Wake

Wake

Sleep

100%100% 100%100%

Howard et al., 2002Howard et al., 2002

0

2

4

6

8

10

12

Baseline night 1 night 2 night 3 night 4

0

5

10

15

20

25

30

35

40

45

MSLT subjective "Fatigue"

Subjective vs. Objective Sleepiness During 4 nights ofSubjective vs. Objective Sleepiness During 4 nights of““Gradual” Sleep Loss (6hrs TIB)Gradual” Sleep Loss (6hrs TIB)

Drake et al., 2001Drake et al., 2001

MS

LT

(m

in)

MS

LT

(m

in)

Su

bjective “F

atigu

e”S

ub

jective “Fatig

ue”

Time in Bed and Excessive Sleepiness

* standard deviation; MSLT = Multiple Sleep Latency Test; Rosenthal L et al. (1993), Sleep 16(3):226-232

Time in Bed (Hours)

MS

LT

Lat

ency

(M

inu

tes)

R2=0.9791

0

2

4

6

8

10

12

14

16

18

8 6 4 0

Crashes and the MSLT (10 year prevalence)

40

42

44

46

48

50

52

54

56

58

60

<= 5 min 5-10 min > 10 min

CrashCrash%%

Multiple Sleep Latency Test GroupsMultiple Sleep Latency Test Groups

Drake et al., prelim. dataDrake et al., prelim. data

N=69N=69

N=204N=204

N=345N=345

Cochran-Armitage Trend Test, p = .048Cochran-Armitage Trend Test, p = .048

SEVERESEVERE MODERATEMODERATE ALERTALERT

Severe Injury Accidents OnlySevere Injury Accidents Only

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

< 5< 5 5-105-10 >10>10

N=69N=69

N=204N=204 N=345N=345

* p < .05;

Multiple Sleep Latency Test GroupsMultiple Sleep Latency Test Groups

% s

ub

ject

s w

ith

cra

sh%

su

bje

cts

wit

h c

rash

Severe injury accidents were those which “prevent normal activities and require hospitalization”

**

Cochran-Armitage, p = .028

SEVERESEVERE MODERATEMODERATE ALERTALERT

100-Car Study: Crashes and Near-crashes

100-Car Study

Drowsiness also appears to affect crashes and collisions at much higher rates than is reported using existing crash databases. Drowsiness was a contributing factor in 12 percent of all crashes and 10 percent of near-crashes, while most current database estimates place drowsiness-related crashes at approximately 2 to 4 percent of total crashes.

Summary

Sleep need is ~8 hours per 24

Sleepiness can be measured physiologically

Reduced sleep below 6 hrs/nt = Excessive sleepiness

Detection of sleepiness/fatigue and judgment is impaired with chronic sleep loss

Many segments of the population are at increased risk

The extent of sleep-related accidents is probably underestimated

Countermeasures = “sleep” not “rest”