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Section B
Measurement and Assessment of Risk
How Do We Measure Alcohol?


Reported intake
-  Self-report
-  Collateral
Observed intoxication
3
How Do We Measure Alcohol?




Blood alcohol concentration (BAC)
-  Blood sample
-  Breath (Breathalyzer)
Urine
-  Alcohol and now metabolites
Biochemical markers SGOT, GGT
Ethyl glucuronide (EtG) and ethyl sulfate (EtS)
-  Used in alcohol treatment programs to monitor
abstinence
  E.g., pilots or surgeons who lost license due
alcoholism
-  Only formed after recent drinking
-  Identifies persons whose BAC now zero but who drank in
past 20-30 hours
4
Alcohol Biomarkers
5
Who Gets Measured?

Bias in case identification:
-  The injured
-  Those with observed behaviors indicative of intoxication
6
When/Where Is It Measured?



On-site
Acute care facility
Necropsy/autopsy
7
Validity of Data on Alcohol and Injuries

Testing practices
-  Test only those suspects that are drunk
-  Delay in testing (metabolism)
-  Decomposition (endogenous alcohol)
8
Validity of Data on Alcohol and Injuries

Testing practices
-  Police officer impression vs. BAC measurement
-  Variation in testing by age and gender
9
History of Alcohol Consumption





What does it mean?
Alcohol use not necessarily related to injuries
BAC may be negative at time of injury
Hangover effect?
Impairment from chronic effects?
10
Hangover






Experimental evidence
Clinical evidence
Marked decrease performance in flight simulator 14 hours
after BAC 100 mg/dl
-  Yesavage et al. (1986)
Sustained attention/reaction time is significantly affected the
day after heavy drinking
Sober trauma center patients
-  46% positive CAGE (a screen for problem drinking)
Started new study to examine the extent to which hangovers
increase crash risk
11
What Is the Role of Alcohol?



How do we assess risk?
Does simply having a high BAC mean there is an increased
risk?
What is the evidence?
12
How Common Is Hazardous Drinking?
Percentage of males reporting having four or more drinks
on any single day by age group and race/ethnicity, U.S.
Source: Jackson et al. (1998).
13
Cross Sectional Studies

Health interview survey:
-  “Children of mothers who were problem drinkers had
higher injury rates than other children.”
14
Cohort Studies

Expected and observed mortality rate in 309 alcoholic
patients
Mortality rate
Type of death
Expected
Observed
Poisoning
0.17
20
Falls
0.68
6
Other accidents
0.78
10
Suicide
1.85
46
Notes Available
15
Case Control Studies

Compare BAC cases and controls
16
Respondent BAC and the BACs of Boating
Fatalities
Respondent BAC and the BACs of boating fatalities, Maryland
Percent positive

17
Comparison of BACs in Fatalities
18
Drinking and Driving
19
Relative Crash Risk by BAC and Driver Age
Source: Adapted from Blomberg et al. (2005).
20
Relative Fatality Risk for Drinking Drivers
21
Case Crossover Study

Variant of case-control study
-  Uses a person as their own control
-  For example, drinking prior to injury compared to
previous day
22
Case Crossover Design

It is a design that compares the exposure to certain agents
during the interval when the event does not occur (control
period), to the exposure during the interval when the event
occurs (hazard period)
Hazard period
Control period
Illness
23
Case Crossover Studies


Risk of MV injury increases by 2.5 after one or two drinks six
hours previous to driving (when compared to no drinks at all)
Risk increases by 5.0 after four or more drinks six hours
previous to driving
Notes Available
24