Even low alcohol concentrations affect obstacle avoidance reactions in healthy senior individuals

Abstract

BackgroundAlcohol is a commonly used social drug and driving under influence is a well-established risk factor for traffic accidents[1]. To improve road safety, legal limits are set for blood alcohol concentration (BAC) and driving, usually at 0.05% (most European countries) or 0.08% (most US states, Canada and UK). In contrast, for walking there are no legal limits, yet there are numerous accounts of people stumbling and falling after drinking. Alcohol, even at these low concentrations, affects brain function and increases fall risk. An increased fall risk has been associated with impaired obstacle avoidance skills. Low level BACs are likely to affect obstacle avoidance reactions during gait, since the brain areas that are presumably involved in these reactions have been shown to be influenced by alcohol. Therefore we investigated the effect of low to moderate alcohol consumption on such reactions.Thirteen healthy senior individuals (mean(SD) age: 61.5(4.4) years, 9 male) were subjected to an obstacle avoidance task on a treadmill after low alcohol consumption. Fast stepping adjustments were required to successfully avoid suddenly appearing obstacles. Response times and amplitudes of the m. biceps femoris, a prime mover, as well as avoidance failure rates were assessed.FindingsAfter the first alcoholic drink, 12 of the 13 participants already had slower responses. Without exception, all participants' biceps femoris response times were delayed after the final alcoholic drink (avg ± sd:180 ± 20 ms; p < 0.001) compared to when participants were sober (156 ± 16 ms). Biceps femoris response times were significantly delayed from BACs of 0.035% onwards and were strongly associated with increasing levels of BAC (r = 0.6; p < 0.001). These delays had important behavioural consequences. Chances of hitting the obstacle were doubled with increased BACs.ConclusionsThe present results clearly show that even with BACs considered to be safe for driving, obstacle avoidance reactions are inadequate, late, and too small. This is likely to contribute to an increased fall risk. Therefore we suggest that many of the alcohol-related falls are the result of the disruptive effects of alcohol on the online corrections of the ongoing gait pattern when walking under challenging conditions.

Prevalence and Determinants of Falls among Older Adults in Ecuador: An Analysis of the SABE I Survey

“…However, low alcohol concentrations among older adults, having considered to be safe for driving, may affect the ability to successfully avoid sudden obstacles in the travel path. Moreover, it is suggested that many of alcohol-related falls are the results of the disruptive effects of alcohol on the online corrections of the ongoing gait pattern when walking under challenging conditions [30]. …”

“…Of relevance, the risk of falling was significantly higher among participants who reported intense regular exercise during the previous year compared to those who did not. This finding may be partly explained by reported changes in postural control among older adults following moderate physical exercise, which may be related to fatigue levels [30]. However, environmental factors and terrain conditions should also be considered as determinants of moderate exercise-related falls among older adults in Ecuador.…”

Pharmacological treatment in Parkinson's disease: Effects on gait

“…Although not a prescribed medication, the care provider should always be aware of alcohol as an acute and chronic cause for gait disturbances and falls [128, 129]. …”

CNS effects of indomethacin: should patients be cautioned about decreased mental alertness and motor coordination?

“…BF response times were determined as the time between obstacle release and the moment at which BF activity exceeded the average control stride activity by at least 2 SDs for more than 30 ms (for example, see Figure 2). See Hegeman et al [13] for more details concerning the obstacle avoidance task. Flow chart showing the progress of all participants throughout the study Secondary cognitive task: auditory Stroop task [15] The participants listened to the words 'high' or 'low' in Dutch, presented in either a high or low pitch.…”