Laparoscopic surgery makes intense demands on cognitive, perceptual and visuospatial abilities, rendering it particularly vulnerable to the effects of alcohol (and also making it a sensitive indicator). In a real-world type experiment, students and experts participated in a study looking at the effects of previous-night’s carousing on next-day’s performance on the Minimally Invasive Surgical Trainer Virtual Reality (for which all participants received training, providing baseline scores).

The first experiment involved 16 male final-year science students, of whom 8 were asked to consume alcohol freely at a group dinner, while the other 8 went to a dinner at which no alcohol was served. The second experiment involved eight laparoscopic experts, all of whom were asked to consume alcohol freely at their group dinner. Participants were tested on the simulator the next day at 9:00 a.m., 1:00 p.m. and 4:00 p.m.

Among the students, those who had consumed excessive alcohol performed considerably worse in terms of time, errors and economy of diathermy (ability to perform technique designed to produce local application of heat), and showed considerable performance variability. Their performance in terms of errors and diathermy was significantly impaired compared to that of the control group. Differences in the time it took participants to perform the tasks were only significant at 9:00 a.m.

Experts were (thankfully!) less impaired by their night out. Nevertheless, they made more errors than they had at baseline, and the difference at 1:00 p.m. was statistically significant. They were also significantly slower during the 1:00 p.m. tests. Performance had returned to baseline levels by 4:00 p.m.

Adding to the growing evidence that social activity helps prevent age-related cognitive decline, a longitudinal study involving 1,138 older adults (mean age 80) has found that those who had the highest levels of social activity (top 10%) experienced only a quarter of the rate of cognitive decline experienced by the least socially active individuals (bottom 10%). The participants were followed for up to 12 years (mean of 5 years).

Social activity was measured using a questionnaire that asked participants whether, and how often, in the previous year they had engaged in activities that involve social interaction—for example, whether they went to restaurants, sporting events or the teletract (off-track betting) or played bingo; went on day trips or overnight trips; did volunteer work; visited relatives or friends; participated in groups such as the Knights of Columbus; or attended religious services.

Analysis adjusted for age, sex, education, race, social network size, depression, chronic conditions, disability, neuroticism, extraversion, cognitive activity, and physical activity.

There has been debate over whether the association between social activity and cognitive decline is because inactivity leads to impairment, or because impairment leads to inactivity. This study attempted to solve this riddle. Participants were evaluated yearly, and analysis indicates that the inactivity precedes decline, rather than the other way around. Of course, it’s still possible that there are factors common to both that affect social engagement before showing up in a cognitive test. But even in such a case, it seems likely that social inactivity increases the rate of cognitive decline.

From the Whitehall II study, data involving 5431 older participants (45-69 at baseline) has revealed a significant effect of midlife sleep changes on later cognitive function. Sleep duration was assessed at one point between 1997 and 1999, and again between 2002 and 2004. A decrease in average night’s sleep from 6, 7, or 8 hours was significantly associated with poorer scores on tests of reasoning, vocabulary, and the MMSE. An increase from 7 or 8 hours (but not from 6 hours) was associated with lower scores on these, as well as on tests of phonemic and semantic fluency. Short-term verbal memory was not significantly affected. The magnitude of these effects was equivalent to a 4–7 year increase in age.

Around 8% of participants showed an increase from 7-8 hours of sleep over the five-year period (7.4% of women; 8.6% of men), while around a quarter of women and 18% of men decreased their sleep amount from 6-8 hours. About 58% of men and 50% of women reported no change in sleep duration during the study period. Some 27% of the participants were women.

The optimal amount of sleep (in terms of highest cognitive performance) was 7 hours for women, closely followed by 6 hours. For men, results were similar at 6, 7 and 8 hours.

Analysis took into account age, sex, education and occupational status. The Whitehall II study is a large, long-running study involving British civil servants. Sleep duration was assessed simply by responses to the question "How many hours of sleep do you have on an average week night?"

A very large Chinese study, involving 28,670 older adults (50-85), of whom some 72% were women, also supports an inverted U-shaped association between sleep duration and cognitive function, with 7-8 hours sleep associated with the highest scores on a delayed word recall test.

I would speculate that this finding of an effect of short-term verbal memory (in contrast to that of the Whitehall study) may reflect a group distinction in terms of education and occupation. The Whitehall study is the more homogenous (mostly white-collar), with participants probably averaging greater cognitive reserve than the community-based Chinese study. The findings suggest that memory is slower to be affected, rather than not affected.

Binge drinking is, unfortunately, most common among adolescents (12-20 years). But this is a time when brains are still developing. Does this make them more vulnerable to the detrimental effects of excessive alcohol?

A study involving adolescent mice has revealed that not only did an alcoholic binge reduce the activity of many neurotransmitter genes, but that gene expression in adulthood was even more seriously reduced. Although this deficit didn’t translate into problems with spatial learning, adult mice that had been exposed to excess alcohol in adolescence were significantly worse on a reversal learning task. Moreover, certain brain regions (the olfactory bulb and basal forebrain) were smaller.

In humans, it is thought that these impairments might translate into greater difficulty in adapting to changed situations, in evaluating consequences and controlling impulses.

Similarly, another recent study involving teenagers (15-21) has found that activity in the prefrontal cortex varied according to how heavily they smoked, with those who smoked most heavily having the least activity.

The 25 smokers and 25 non-smokers were tested on a Stop-Signal Task, which tests a person’s ability to inhibit an action. Despite the differences in activity level, smokers and non-smokers performed similarly on the task, suggesting that other brain areas are in some way compensating for the impaired prefrontal cortex. Nevertheless, reduced activity in the prefrontal cortex, which is still developing in adolescence, does suggest long-term consequences for decision-making and cognitive control.

In a study involving 44 young adults given a rigorous memorizing task at noon and another such task at 6pm, those who took a 90-minute nap during the interval improved their ability to learn on the later task, while those who stayed awake found it harder to learn.

The degree to which the nappers were refreshed correlated with the amount of stage 2 non-REM sleep they experienced. This sleep phase is characterized by sleep spindles, which are associated with brain activity between the hippocampus and prefrontal cortex. Spindle-rich sleep occurs mostly in the second half of the night, so those who don’t get their quota of sleep are probably getting less.

The finding confirms the idea that learning ability decreases the more time you spend awake.