Improving road safety and health: Understandng kava's impact on driver fitness.

Abstract

Kava (Piper methysticum) is a traditional and culturally significant Pacific Island beverage that produces a soporific relaxant effect. Kava’s psychopharmacological action is similar to the anti-anxiety drug Benzodiazepine. Traditional users often consume the kava drink at volumes as much as 30 times greater than pharmacologically recommended doses. Prompted by concerns regarding driver impairment post kava drinking, a study was undertaken replicating traditional kava sessions in terms of duration and kava consumption, to investigate the effects of kava on driving capability. Kava consumers (n=20) attended two six-hour kava sessions, each participant drinking an average 3.52 litres of kava. A non-kava consuming control group (n=20) was included in the study. At baseline all the participants completed computerised industry standard driver safety assessment tests (Vienna Test System: Traffic WAFA Alertness and WAFG Divided Attention) to measure reaction time, perception and attention. Re-testing was conducted at hourly intervals over the six-hour period. Pre/post analysis compared person to person and between groups change. Statistical modeling was based on ANOVA, independent t-tests and Bayesian analysis. Data analysis indicated no statistically significant (p<0.05) difference between reaction time and divided attention, both within individuals and between groups, at any measurement point over the six-hour testing period. The mean reaction time and divided attention time at the baseline measurement was 249.95msec (milliseconds) and 583.58msec respectively. The control and active group mean reaction time at the final test was 256.70msec and 271.8msec respectively. The mean divided attention times for the control and active groups at the final test were 499.75msec and 568.32msec. Kava at traditional consumption volumes was not correlated to response latency or impairment on perception and attention tasks, when measured using authoritative driver assessment tests. From this it could be inferred that kava use at traditionally influenced consumption volumes does not compromise driver safety. However, it can be argued that current industry standard accepted cognitive measures of driver safety, assess impairment from the use of euphoric and hallucinogenic drug substances (such as alcohol and marijuana), and fail to account for kava’s unique form of ‘intoxication’. Further research beyond the assessment of these two cognitive functions is, it seems, desirable to better understand if kava has any effect on driver ability. The study was funded by the Health Research Council of New Zealand (16/462) and the University of Waikato, and the test battery was generously donated by Vienna Tests Systems, Germany.