Commentary: why is the odds ratio for involvement in serious road traffic accident among drunk drivers in Norway and Finland higher than in other countries?

Substance use and driver fatality in Norway: An expanded case-control study

OBJECTIVE

Using alcohol or psychoactive drugs before driving a motor vehicle may increase the risk of crash involvement, injury, and death. This is better documented for alcohol than for drugs. The aim of this study was to expand a previous case-control study on substance use and driver fatality by doubling the number of cases and controls, and hence improve the statistical power and enable the analysis of combined substance use.

METHODS

We collected data on alcohol and drug use from all 1197 drivers of cars and vans who were fatally injured in road traffic crashes in Norway between 2005 and 2020 ('cases') by analyzing blood samples or reviewing other information on substance use. We also collected data on alcohol and drug use among 17,219 drivers in random road traffic ('controls') by analyzing oral fluid samples. Substance use was converted to dichotomous variables (no use/use). We used unconditional logistic regression to estimate adjusted odds ratios (aORs) with 95% confidence intervals (CIs) of driver fatality for mutually exclusive substance groups, adjusted for sex, age, geographic region, urban centrality class, and time interval of the week.

RESULTS

Compared to no substance use, the aOR (95% CI) for driver fatality was for alcohol 91 (61-137), stimulants (primarily amphetamines) aOR 22 (9-56), benzodiazepines and z-hypnotics (BZDs) aOR 4.0 (2.7-5.9), tetrahydrocannabinol (THC) aOR 3.4 (1.7-6.7), and opioids aOR 1.4 (0.4-4.9). The aOR for any polysubstance use was 168 (96-297). The combinations of BZDs with stimulants or THC were associated with markedly higher aORs for driver fatality than the use of single substance groups.

CONCLUSIONS

Alcohol and polysubstance use are the most important predictors of fatal injury, followed by stimulants.

All-cause and cause-specific mortality among individuals imprisoned for driving under the influence of alcohol and drugs in Norway (2000-2016): a retrospective cohort study

AIMS

To describe all-cause and cause-specific mortality and to investigate factors associated with mortality among individuals imprisoned for driving under the influence (DUI) of alcohol and psychoactive drugs in the Norwegian prison population.

DESIGN

Retrospective cohort study. The Norwegian prison registry was linked to the Norwegian Cause of Death Registry (2000-2016).

SETTING

Norway.

PARTICIPANTS/CASES

The cohort consisted of 96 856 individuals imprisoned in Norway over a 17-year period obtained from the Norwegian prison registry.

PRIMARY AND SECONDARY OUTCOME MEASURES

Adjusted ORs (aOR) with 95% CI were calculated for death due to any, natural and unnatural causes of death. Analyses were stratified according to DUI convictions: no DUI convictions, only DUI convictions (DUI only), DUI and at least one other drug and alcohol conviction (DUI drug), and DUI and at least one conviction other than drug and alcohol conviction (DUI other).

RESULTS

In total, 29.3% individuals had one or more imprisonments for DUI. The risk of all-cause mortality was elevated for those convicted for DUI, but only in combination with other types of crimes (DUI drug: aOR=1.5, 95% CI 1.4 to 1.6, DUI other: aOR=1.2, 95% CI 1.1 to 1.4). The risk of death from natural causes was significantly elevated for DUI drug (aOR: 1.8, 95% CI 1.6 to 2.0) and for DUI other (aOR=1.3, 95% CI 1.1 to 1.6). The risk of death from unnatural causes was lower for DUI only (aOR=0.8, 95% CI 0.7 to 0.9) and elevated for DUI drug (aOR=1.5, 95% CI 1.3 to 1.6).

CONCLUSIONS

The risk of all-cause mortality was significantly elevated for those convicted of DUI, but only in combination with other types of crimes.

Alcohol and driving-How bad is the combination? A meta-analysis

OBJECTIVE

The objective of this study was to summarize existing knowledge on the association between driving under the influence of alcohol and road safety outcomes and to assess factors that may explain why these estimates vary.

METHODS

Based on studies of the association between blood alcohol concentration (BAC) levels and crashes, we used multilevel metaregression to calculate summary effects of BAC level and analyze potential moderators of the association.

RESULTS

Based on 60 studies and 393 effect estimates, we found that BAC level, outcome severity, use of hospital data, and geographical region contributed to heterogeneity in results.

CONCLUSION

The effect of BAC on crash and injury risk and culpability is stronger at higher BAC levels and for more serious outcomes. The relationship between BAC level and outcome is approximately exponential. The relationship is stronger in studies from Nordic countries than in studies from other countries, possibly because of the relatively low level of drunk driving in these countries. Studies based on hospital data and studies using non-crash-involved control groups find smaller effects on average.

Challenges and common weaknesses in case-control studies on drug use and road traffic injury based on drug testing of biological samples

PURPOSE

To determine and discuss common weaknesses and errors in case-control studies on the association between drug use and road traffic crash injury among drivers and recommend improvements for future studies.

METHODS

A search for case-control studies published between 2000 and 2016 was performed using PubMed and other databases in addition to manual search. The used methodologies were compared with requirements and recommendations for case-control studies as well as current knowledge on the interpretation of drug concentrations in biological samples.

RESULTS

Seventeen studies were identified. The major difficulties in the studies were related to likely selection bias, information bias, and confounding. In some studies, the definition of drug exposure was different for controls than for cases, generating potentially serious errors in the odds ratio estimations. Other weaknesses include lacking explanation of the assessment of drug exposure, missing covariates, lacking description of statistical methods, and lack of discussion of bias and confounding.

CONCLUSIONS

Many of the observed challenges and weaknesses can be overcome or reduced. Recommendations for future studies are presented.

The epidemiologic principles underlying traffic safety study designs

This article describes the epidemiological principles underlying four observational study designs commonly used to assess traffic safety: the case-control, case-crossover, culpability and quasi-induced exposure designs. We focus in particular on the specific challenges for preventing bias using each design. Whereas recruiting controls representative of the source population poses a special challenge in case-control traffic safety studies, case-crossover designs are prone to recall bias, and culpability and quasi-induced exposure studies can be undermined by difficulties assigning crash responsibility. Using causal diagrams and worked examples, we provide a simple way to teach traffic safety designs to epidemiologists and to encourage proper application of epidemiological principles among researchers designing traffic safety studies.

Which drugs are associated with highest risk for being arrested for driving under the influence? A case-control study

The aim of this study was to determine the association between drug type and arrest for driving under the influence of drugs (DUID) by calculating odds ratios (ORs) using a case-control design. A DUID arrest is in most cases related to aberrant or risky driving and might therefore be regarded as a proxy for a drug related traffic crash. The 'cases' were 2738 drivers arrested on suspicion of drugged driving from April 2008 to March 2009 with blood alcohol concentrations below the legal limit of 0.2g/L; 794 were arrested due to involvement in road traffic crashes, whereas 1944 were arrested for other reasons, mainly dangerous driving, suspected impairment when stopped in traffic controls, or because of phone calls to the police from other road users or observers. The 'controls' were 9375 random drivers in normal traffic, also with alcohol concentrations below this limit. Blood samples from 'cases' and oral fluid samples from 'controls' were analyzed for 15 drugs that have legislative concentration limits in Norway, in addition to two other commonly detected psychoactive drugs. The most prevalent illicit drug in the control group was tetrahydrocannabinol (THC; 0.58%), which was also commonly found in samples from drivers arrested due to road crash (15.6%) or arrested for other reasons (21.8%). Amphetamine/methamphetamine was most prevalent among arrested drivers involved in crashes (30.6%) and drivers arrested for other reasons (56.9%), whereas only 0.18% of the control group was positive for amphetamine/methamphetamine. The single-use substances which gave highest OR for police arrest were amphetamine/methamphetamine, alprazolam, clonazepam and oxazepam. The majority of the alprazolam and clonazepam findings were probably due to non-therapeutic use of medicinal drugs purchased on the illegal market. Combinations of two or more drugs yielded higher ORs than the use of single substances; combinations of amphetamine/methamphetamine and benzodiazepines gave the highest risk.