Scientists have learnt why people lose their memory after drinking alcohol
The authors of a new study have identified three factors responsible for so-called alcohol blackout - a common consequence of drinking alcohol when people experience memory lapses.
A team of scientists from the Edna Bennett Pierce Centre for Prevention Research and from the Department of Biobehavioural Health at the University of Pennsylvania in the US set out to find out whether the way people drink alcohol predicts alcohol-induced memory lapses. They reported their findings in a paper for the journal Alcoholism: Clinical and Experimental Research.
Memory impairment is a common consequence of alcohol use: according to a 2022 study, of 1,700 college students, about 80 per cent reported at least one blackout episode. The drinker remains conscious (up to a point), interacts with others, and then partially or completely fails to remember what happened the night before.
In addition to the periods of amnesia themselves, a person may experience symptoms of mental and behavioural disorders on the background of alcohol consumption. Therefore, understanding the causes of these memory lapses will help prevent harm from alcohol abuse.
The authors of previous research papers have concluded that the amount drunk is not the only factor that triggers memory loss. To find out the other causes and not rely solely on self-reports from drinkers, the American scientists used BACtrack Skyn wrist-worn transdermal alcohol concentration sensors. They measure biomarkers of intoxication in near real time.
The study involved 79 students at a large university in the northeastern United States who were prone to "risky" drinking, aged 18 to 22. All completed a small baseline survey and visited a lab, where they were given sensors to wear from 5 p.m. Thursday to Sunday morning for a month. Volunteers also completed questionnaires each morning about whether they had been drinking the night before and whether they remembered the events of the evening.
The reward amount for one person was up to $75, and there was still an opportunity to win one of eight $100 gift cards for participating in the experiment.
Over the course of the study, researchers recorded 486 episodes of drinking and 147 episodes of amnesia. More than two-thirds (69.3 per cent) of the students experienced a blackout at least once. To test the hypothesis, the researchers built multilevel logistic models and examined how individual measures of transdermal alcohol concentration - the rate and duration of its rise, as well as reaching a peak - were associated with memory lapses.
"Our hypothesis was completely confirmed. We identified three biomarkers of increasing alcohol intoxication - its rate of attainment, duration, and peak value - that predict the likelihood of blackout in college student drinkers. The results support the notion that how one drinks is important in predicting the risk of alcohol-induced blackouts," the researchers said.
Thus, on days when alcohol intoxication rates rose rapidly in the participants' blood, the risk of memory lapses increased by 2.69 times; when peak alcohol concentrations were highest - by 2.93 times; when intoxication rates increased for a long time (we are talking about the number of hours of drinking) - by 4.16 times. When all three factors occurred, only the duration of reaching intoxication showed a significant correlation with blackouts.
"To reduce the risk [of memory lapses], it is important to consider how a person consumes alcohol, not just the amount. Both the rate of intoxication, its peaks, and the time at which the drinker reaches the peak are important in predicting alcoholic amnesia. These predictors have implications for prevention," the researchers stated.
They also noted some limitations of the study: the small number of participants, with the majority being white (86.1 per cent) and female (55.7 per cent); the duration of the experiment was one month, which fell on St Patrick's Day (associated with drinking) and Easter weekend (students tend to go home where they drink less). Sensors may also have missed days with less heavy drinking. Finally, some young people may not have realised during the morning survey, when they had not yet met up with friends and exchanged party experiences, that they did not remember certain moments.