Low blood alcohol levels. Experimental study on attention and body sway control functions

Objective

Attempting to prevent alcohol-related road accidents requires sensitive, reliable and easy-to-use methods and instruments for ascertaining drivers’ state of intoxication. This paper examines the scientific validity of a method for assessing psychomotor performance combining measurement of neurosensory functions with the effect of low blood alcohol levels: body sway control and attention functions.

Methods

A double-blind, placebo-controlled study, with cross-over and random distribution on the effects of low blood alcohol levels. Psychomotor performance and body sway control were studied in 16 healthy volunteers after they had drunk a small dose of ethyl alcohol (0.5 g/kg) or placebo. Neurosensory and psychomotor functions were assessed by a Divided Attention Test (DAT), composed of the association between one test exploring short-term memory (Memory Test) and one exploring attention (Response Competition Test). Alterations in body sway were recorded by stabilometry. Tests were administered at 30, 60, 120 and 180 min after intake of alcohol. After a wash-out period of at least one week, subjects repeated the test after taking a second dose of alcohol or placebo. Blood alcohol concentrations were monitored by analysis of concentrations in expired air.

Results

A BAC under 50 mg/dL did not reveal statistically significant impaired memory capacities or motor coordination. Instead, statistically significant oscillations of body sway were measured (p-values = 0.0001), especially when stabilometry was associated with deviant stimuli like those of the DAT (p-values = 0.0001).

Conclusions

This study showed: (1) impaired performance, at the limits of statistical significance, on a complex psychometric test like the DAT; (2) some cognitive, attentive and visual perceptive functions are not compromised or at least not in a statistically significant manner; (3) a considerable alteration in the capacity for control of body sway after intake of alcohol becomes further and massively impaired when deviant stimuli are given; (4) this impairment appeared early and was more marked 1 and 2 h after intake of alcohol.