Energy drinks are associated with insomnia and poor-quality sleep, according to a large study that suggests just one can a month raises the risk of disturbed sleep.
Millions consume the products, which contain an average caffeine content of 150mg per litre as well as sugar, vitamins, minerals and amino acids. They are marketed as boosters of mental health and physical performance, and are popular with young people in particular.
While there is already evidence to suggest they reduce sleep quality, until now it has been unclear exactly which aspects of sleep might be more or less affected, or whether there are any sex-specific differences in these effects.
A study involving more than 53,000 people aged between 18 and 35 in Norway has shed fresh light on the potential negative effects of energy drinks.
Researchers found those who consumed them every day slept about half an hour less than those drinking them occasionally or not at all.
And the higher the frequency of consumption, the fewer hours of nightly sleep clocked up. But even just the occasional can – one to three times a month – is linked to a heightened risk of disturbed sleep, the researchers found. Their findings were published in the BMJ Open journal.
Men having two or three drinks a week were 35% more likely to have a bedtime after midnight, 52% more likely to sleep less than six hours, and 60% more likely to wake in the night than those who did not or rarely drank them.
Women were 20% more likely to have a bedtime after midnight, 58% more likely to sleep less than six hours, and 24% more likely to wake in the night.
People consuming the drinks daily had more issues overall with waking after falling asleep and took longer to fall asleep, and slept less overall than those not drinking them. The study also found that the more people drank, the less sleep they had.
For women drinking energy drinks daily, 51% reported suffering insomnia, compared with 33% of women who drank the drinks occasionally or never.
Among men, 37% of daily drinkers suffered insomnia, compared with 22% of those who rarely or never had the drinks.
Men who were daily drinkers were more than twice as likely to say they slept fewer than six hours a night as infrequent drinkers, while women were 87% more likely to do so.
But even those having one to three energy drinks a month had bigger sleep issues than those who never touched them, the study suggested.
This was an observational study, and as such no firm conclusions can be drawn about cause. The researchers acknowledged that reverse causality – whereby energy drink consumption could be a consequence of poor sleep rather than the other way round – may explain the associations found.
Nevertheless, the researchers from the universities of Bergen and Oslo concluded: “ED [energy drink] consumption was a strong determinant for negative sleep outcomes.
“Even small amounts of ED were associated with poorer sleep outcomes, which warrant more attention towards the consequences of consuming ED among college and university students.”
