Analysis of body sway pattern after alcohol ingestion in human subjects.

Movements of the centre of gravity during 60 s of standing with eyes closed and eyes open were analysed before and after alcohol ingestion up to 8 h in 37 healthy human subjects. Blood alcohol and acetaldehyde concentrations (BAC and BAcHC) were measured simultaneously. Among the parameters analysed, area of posturogram was the most sensitive indicator; it increased to 3.8 times that of the control value at 60 min, after 3.5 ml/kg of ingested whisky (mean BAC of this group was 1.4 mg/ml), with the eyes open. The Romberg ratio, which denotes eyes closed relative to eyes open, remained constant. By contrast, there was little change in stabilometry in cases of 1.2 ml/kg of whisky ingestion (mean BAC at 60 min was 0.58 mg/ml). It is considered that body sway starts to increase when the BAC level exceeds 0.6 mg/ml on average; this value is only higher than the threshold of positional alcohol nystagmus. Correlation coefficients between BAC and each parameter of the stabilogram in the eyes open condition, such as area, X- and Y-axis diameters, and velocity of body sway, were 0.53, 0.45 and 0.48, respectively (p less than 0.01). There was no positive correlation between BAcHC and these parameters.