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Mar 16, 1985 - underlying drinking and driving laws in many countries.2 Most previous studies of road traffic accidentshave used stated alcohol consumption ...
BRITISH MEDICAL JOURNAL

VOLUME 290

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16 MARCH 1985

MEDICAL PRACTICE

Contemporary Themes Are problem drinkers dangerous drivers? An investigation of arrest for drinking and driving, serum y glutamyltranspeptidase activities, blood alcohol concentrations, and road traffic accidents: the Tayside Safe Driving Project JAMES A DUNBAR, SIMON A OGSTON, A RITCHIE, M S DEVGUN, JAMES HAGART, BRIAN T MARTIN Abstract Serum y glutamyltranspeptidase activity was measured in 440 drivers at the time of arrest for driving under the influence of alcohol. The results were compared with information gathered by the arresting police officer. One third of drivers over the age of 30 had abnormal y glutamyltranspeptidase activities at the time of arrest. Among drivers who required a driving licence for their work, and older drivers, a disproportionately high number had raised y glutamyltranspeptidase activities indicating problem drinking. In drivers over the age of 30 a strong association was found between y glutamyltranspeptidase activities and road

Departments of Forensic, Community and Occupational, and Biochemical Medicine, University of Dundee, and Tayside Police, Scotland JAMES A DUNBAR, MRCGP, DMJ, police surgeon and honorary lecturer in forensic medicine SIMON A OGSTON, MA, MSC, medical statistician A RITCHIE, chief inspector

Department of Biochemistry, Law Hospital, Carluke, Lanarkshire M S DEVGUN, PHD, MIBIOL, senior clinical biochemist Social Psychology Research Unit, University of Kent, Canterbury, Kent JAMES HAGART, MSC, research fellow Area Department of Pathology, Exeter, Devon BRIAN T MARTIN, BSC, PHD, principal biochemist

Correspondence to: Dr J A Dunbar, Department of Forensic Medicine, Royal Infirmary, Dundee DD1 9ND.

traffic accidents but not alcohol concentrations or previous convictions. These findings argue against the Department of Transport's criteria for high risk offenders and indicate a clear need for new measures against problem drinkers among drinking and driving offenders. Introduction In 1976 the Blennerhassett Committee recommended that those at high risk among drinking and driving offenders should be identified.' Since May 1983 the Road Traffic Act has defined high risk offenders as drivers who are convicted of drinking and driving on two occasions within 10 years and have alcohol concentrations two and a half times the legal limit or refuse to provide a specimen. High risk drivers are investigated by the medical advisers of the Department of Transport for evidence of dependence on alcohol or other drinking problems. This implies that problem drinking, as distinct from driving under the influence of alcohol, is accepted as an important factor in traffic safety. The relation between alcohol concentrations and road traffic accidents has been accepted for two decades and is the rationale underlying drinking and driving laws in many countries.2 Most previous studies of road traffic accidents have used stated alcohol consumption or alcohol concentrations, or both, to identify problem drivers, although the accuracy of these methods is in doubt and alcohol concentrations are dependent on the time elapsed between alcohol consumption and arrest. Recent research has also shown that the relation between alcohol concentrations and accidents is complicated by other factors,34 and particular attention

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has been paid to the effects of age and problem drinking.5-9 Evidence submitted to the Blennerhassett Committee by the British Medical Association and the Medical Commission on Accident Prevention favoured a single, lower, criterion blood alcohol concentration of 33 mmol/l (150 mg/100 ml) indicating potential problem drinking. Little research into high risk offenders has been conducted, and it remains to be shown that high risk offenders as defined in the Road Traffic Act are synonymous with those offenders whom Blennerhassett sought to identify.9 Serum enzyme y glutamyltranspeptidase activity is generally accepted to be a reasonably sensitive indicator of chronic excessive alcohol consumption'"'2 and has been used in four studies of drivers. 13-16 As a single drinking binge does not increase y glutamyltranspeptidase activities in drivers with either normal or abnormal activities the activity of the enzyme measured at the time of arrest has been recommended as a simple way of helping to identify many people who chronically consume excessive amounts ofalcohol. 1i We undertook the following examination of the relations between y glutamyltranspeptidase activities, alcohol concentrations, age, and accidents among drivers arrested for drinking and driving to help clarify the position regarding alcohol consumption and road traffic accidents and facilitate the assessment of offenders who are also problem drinkers.

Subjects and methods Motorists arrested for drinking and driving in Tayside Region over one year and opting to give a blood sample were invited to participate in this study; 440 (96%) (of whom 429 (97-5%) were men) agreed to do so. At the time of arrest 5 ml blood was taken and divided into three samples: one was given to the driver, the second was analysed for blood alcohol concentration by the public analyst, and the third was used to measure the serum activity of y glutamyltranspeptidase using a centrifugal fast analyser (37°C). Other liver enzyme tests were not carried out because of sample instability.'7 An examination to detect drugs or diseases known to raise serum y glutamyltranspeptidase activity was carried out, but none such was detected. The arresting police officer filled out a questionnaire for all drivers. This identified the type of vehicle being driven, whether the driver was the owner, the reason for the arrest, whether the driver was involved in an accident, and whether he required a driving licence for his job. With the driver's consent a list of his previous drinking and driving convictions was obtained from the police computer. Only 23 (5-3%) of participants refused this consent. In subsequent tables blood alcohol concentration is categorised as greater or less than 33 mmol/l, a limit that conforms with the British Medical Association's recommended criterion of high risk offenders and corresponded to the approximate median concentration of the sample. In addition, 50 IU/l was used as the limit to define high and low y glutamyltranspeptidase activities. Significance tests for categorical data were used-namely, Fisher's exact test for 2 x 2 contingency tables and x2 tests for larger tables.

Results Table I shows the distribution of variables recorded by the arresting officer across three age groups (under 30, 30-44, and 45 and over). This indicates that a third of the drivers had been arrested for impaired driving and a quarter had been involved in an accident. Significant differences were evident across age groups for all variables except the proportion of drivers who had been involved in accidents. Table II shows the numbers and proportions of subjects who had raised y glutamyltranspeptidase activities, tabulated by age and variables in the police questionnaire. Overall, one fifth (91) of the drivers had raised y glutamyltranspeptidase activities, the prevalence being 10 2%, 31 5%, and 29-3% in drivers aged under 30, 30-44, and 45 and over, respectively. Among young drivers the only significant difference in y glutamyltranspeptidase activities was associated with type of vehicle driven, drivers of heavy goods or commercial vehicles contributing disproportionately to the number of people with a raised y glutamyltranspeptidase activity. Among drivers in the 30-44 age group there were significant differences in y glutamyltranspeptidase activities associated with reasons for arrest, accident involvement, and whether driving licences were required for the driver's occupation. In the 45 and over age group reasons for arrest showed a significant relation. Raised y glutamyltranspeptidase activities were more common in drivers involved in accidents and arrested as the result of an accident and in those who required a driving licence for their jobs, including

BRITISH MEDICAL JOURNAL

VOLUME 290

16 MARCH 1985

drivers of public service and heavy goods vehicles. There was no significant relation between previous drinking and driving convictions and raised y glutamyltranspeptidase activities. Table III summarises the interrelation between blood alcohol concentration, y glutamyltranspeptidase activities involvement, and age for 377 drivers across two age groups (under 30 and over 30) on whom complete information was available. Of drivers aged below 30, only one of those involved in an accident (2-4%) had a high y glutamyltranspeptidase activity. TABLE i-Distribution ofpolice questionnaire variables by age. Figures indicate numbers (%) subjects Subjects aged:

Total

yearst Blood alcohol concentration: 110 (61-5) 33 mmol/1 37 Unknown 179 Total Car owner: 135 (62-5) Yes 81 (37 5) No Reason for arrest: 63 (30-1) Moving traffic offence 31 (14-8) Routinestop 63 (30-1) Impaired driving 8 (3-8) Information received 44 (21-1) Accident 7 Other 209 Total Type of vehicle driven: 166 (77-6) Car Heavy goods or 20 (9-3) commercial vehicle 28 (13-1) Motorcycle 2 Other 214 Total Driving licence required for occupation: 73 (33-8) Yes No 143 (66-2) Previous drinking/driving conviction: 22 (11-2) Yes 194 (89-8) No Involved in accidents? 49 (22-7) Yes 167 (77 3) No

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