Modeling Fatigue Predicting Performance

1. Modeling Fatigue Predicting Performance Steven R. Hursh, Ph.D. Professor, Johns Hopkins University School of Medicine and Program Manager, Biomedical Modeling and Analysis Science Applications International Corporation, 301-785-2341 Hurshs@saic.com

2. Outline • Fatigue overview. • Drivers of fatigue • Biomathematical models of fatigue and the Sleep, Activity, Fatigue, and Task Effectiveness (SAFTE) Model • Fatigue analysis tools and the Fatigue Avoidance Scheduling Tool (FAST) • Soldier monitoring to assess fatigue • Aviation applications

3. Operational Definition • Fatigue is a complex state characterized by a lack of alertness and reduced mental and physical performance, often accompanied by drowsiness. • Fatigue is more than sleepiness and its effects are more than falling asleep. DOT Human Factors Coordinating Committee, 1998

4. Symptoms Operational Consequences Measurable Changes in Performance Lapses in attention and vigilance Delayed reactions Impaired logical reasoning and decision-making Reduced “situational awareness” Low motivation to perform “optional” activities Poor assessment of risk or failure to appreciate consequences of action Operator inefficiencies Symptoms versus Root Causes • Root Cause Analysis • Fatigue is one potential root cause • No direct measure, physiological marker, or “blood test” for fatigue • However, the conditions that lead to fatigue are well known and • A fatigue model can help evaluation and integrate the specific conditions of an accident to determine if fatigue was involved.

5. Major Fatigue Factors • Time of Day: between midnight and 0600 hrs. • Cumulative Sleep Debt: more than eight hours accumulation. • Acute Sleep Debt: less than eight hours in last 24 hrs. • Continuous Hours Awake: more than 17 hours since last major sleep period. • Time on Task: continuous time doing a job without a break.

6. Major Consequences of Fatigue • Three Mile Island (1979): 4:00 a.m. and involved human error. • Chernobyl Nuclear Reactor Meltdown (1986): 1:30 a.m. and involved human error. • Exxon Valdez (1989): 12:04 a.m. One major cause: “The failure of the third mate to properly maneuver the vessel, possibly due to fatigue and excessive workload.” • Operation Desert Storm (1990): More friendly fire losses than enemy losses, many due to sleep deprivation.

7. Benefits of Reduced Fatigue • More capable workforce – “force multiplier” • Higher level of performance (higher efficiency , increased productivity, fewer errors/incidents/accidents) • Fewer accidents/incidents • Reduced absenteeism, increased availability • Improved health • Higher moral • Improved safety, reduced workman’s compensation • Reduced regulatory pressure • Improved labor relations

8. Sleep History and Time on Duty Time of Day CIRCADIAN RHYTHM CUMULATIVE SLEEP DEBT ALERTNESS & COGNITIVE PERFORMANCE ALERTNESS & COGNITIVE PERFORMANCE Daily Variations in Effectiveness

9. Major Inputs for Predicting Fatigue • Time of Day • Amount, quality and timing of sleep • Individual factors • Phase of the circadian “pacemaker” • Individual sleep need or sensitivity to sleep loss

10. Sources of Information • Time of day: both the clock time and the time zone – inferred from location information • Sleep: • Direct measurement • Infer from work pattern (AutoSleep) • Duty periods and Critical Events: • Drives sleep opportunities • Determines critical periods for performance prediction • Individual factors • Circadian phase: temperature or hormonal oscillations • Sleep need: no simple test at this time

11. SAFTE • The Sleep, Activity, Fatigue, and Task Effectiveness (SAFTE) Model is based on 12 years of fatigue modeling experience and over $2.6M of US DOD investment. • Validated against laboratory and simulator measures of fatigue. Work place calibration is underway. • Now accepted by the US DOD as the common warfighter fatigue model. • Independently compared to six models from around the world and judged to have the least error (Fatigue and Performance Workshop, Seattle, 2002).

12. SLEEP REGULATION 12 PERFORMANCE MODULATION Schematic of SAFTE™ Simulation Model Sleep, Activity, Fatigue and Task Effectiveness Model DYNAMIC PHASE CIRCADIAN OSCILLATORS COGNITIVE EFFECTIVENESS SLEEP DEBT FEEDBACK LOOP SLEEP INTENSITY SLEEP RESERVOIR SLEEP ACCUMULATION (Reservoir Fill) INERTIA SLEEP “QUALITY” FRAGMENTATION PERFORMANCE USE (Reservoir Depletion) POC: Steven Hursh, PhD, Tel: 410-538-2901 12

13. Walter Reed Restricted Sleep StudySAFTE Model (red line) Predicts the Average Results with Precision Baseline Restriction Recovery

14. Accident Likelihood Increases with Decreasing Effectiveness

15. Practical Software for Implementation • Fatigue Avoidance Scheduling Tool (FAST) • FASTis a fatigue assessment tool using the SAFTE model • Developed for the US Air Force and the US Army. • DOT/FRA sponsored work has lead to enhancements for transportation applications. • Sleep estimation algorithm • Schedule grid data entry tool • Wizards and dashboard • Standard data file format • DOT field calibration underway.

16. Effectiveness Adjustable Criterion Line Lower Percentile (e.g. 20%) Sleep Periods in Blue Work Periods in Red FASTGraphical Screen Options

17. Lapses in Attention with Reduced Sleep Successive days of reduced sleep

18. Lapse Index Graph Lapse Index probably similar to values from PERCLOS drowsiness monitor.

19. Individual VariabilityDisplay Lowest 20 percentile, for example

20. BAC Scale The effects of fatigue may be compared to the effects of blood alcohol to calibrate the severity of fatigue Fatigue as predicted by FAST and the effects of alcohol are not identical. Arnedt, J.T., Wilde, G.J., Munt, P.W., MacLean, A.W. “How do prolonged wakefulness and alcohol compare in the decrements they produce on a simulated driving task?” Accid Anal Prev., 2001 May;33(3):337-44. Dawson, D., Reid, K., 1997. “Fatigue, alcohol and performance impairment.” Nature 388, 23.

21. Flags are fatigue indicators Value at point in schedule Criteria Dashboard InformationAnalysis System Could Report Fatigue Indicators Content based on fatigue analysis workshop hosted by NTSB and conducted by Drs. Mark Rosekind and David Dinges, funded by FRA Office of Safety. • Sleep (last 24 hrs) • Chronic Sleep Debt • Hours Awake • Time of Day • Out of Phase • Performance Values • Effectiveness • Mean Cognitive • Lapse Index • Reaction Time • Reservoir

22. Percent of Error Sources of Uncertainty • Incomplete work/rest history, especially sleep history • Differences in personal sleep physiology • Bio-rhythms • Sleep need • Other personal factors • Health • Medications • Inaccuracies in our modeling and analysis • Lack of knowledge about specific changes in behavior Actigraphy Temperature Sensing & GPS Biomedical recordings Continuous model improvement Performance Monitoring

23. Trip Plan Editor

24. Summary of Effectiveness by Waypoints

25. Summary of Duty Periods

26. B2 Stealth Bomber

27. Lounge Chair Solution for In-flight Naps

28. Commercial Interest • Two major airlines • The two largest business aviation companies • Two large oil companies • Five largest freight railroads • A dozen electric power companies • Fatigue consultants • Two foreign governments

29. Monitoring Fatigue and Predicting Performance If you would like more information, call………… Steven R. Hursh, Ph.D. Professor, Johns Hopkins University School of Medicine and Science Applications International Corporation, 301-785-2341 Hurshs@saic.com

30. Actigraph Recording for Sleep Estimation • Actigraph Recording Device: Records whole body activity and permits inferences about sleep timing, quality and quantity.

31. Actigraph and Fatigue Assessment Software (FAST) Actigraph Recording Device FAST Performance Assessment Tool Ambulatory Monitoring, Inc. • Technical Concept • Estimates person’s actual sleep and circadian rhythm based on non-invasive measurement of activity pattern. • Data could be transferred to computer for fatigue assessment • Built-in model could gives user real-time estimate of performance effectiveness. • Allows user to plan future activities to maximize capability using FAST. • Gives commanders real-time assessment of fatigue status of entire unit • Current status • Fatigue model sufficiently accurate for generic applications. • Actigraphy devices are now small, reliable, and highly sensitive. • Planning tool is available today. Used to plan military operations and training. Used to estimate fatigue in civilian transportation operations. • Can accept geographic waypoints during schedule to estimate sunlight and jet lag.

32. 8 7 6 5 4 3 2 1 Aggregated analysis across individuals and units. Permits sort of units by aggregated fatigue score. 0 A B C D E F G H I J Unit Fatigue Analysis System Sensors  Soldier Computer  Unit Level Receiver and Computer  Aggregate Analysis

33. Sample Flight Plan AnalysisNot an Actual Flight Plan Tokyo SIN BKK HOU HKG PEK

34. Tools for Aviation • Waypoints and international airport database • Trip Planner • Zulu time and world-wide local time • Waypoint and critical event effectiveness summary table • Duty period summary table • Mission Timeline

35. Printable Mission TimelineUser Selectable Features