Mixing alcohol and energy drinks 'may be a risky cocktail'

"Mixing energy drinks with alcohol could be a risky combination, leading to a greater risk of accidents and injuries," BBC News report.

A review of evidence found a number of potential risks, but the picture was not as clear-cut as reported.

Energy drinks are drinks that contain high amounts of caffeine. Some people mix them with spirits such as vodka.

Canadian researchers aimed to look at the published evidence on whether mixing alcohol with energy drinks is linked to an increased risk of harm or injury.

The researchers identified 13 studies – overall, 10 of them reported an increased risk of injury when drinking the mixture compared with alcohol on its own.

One possible factor discussed in the review is that the stimulant effects of caffeine could combine with the inhibition-lowering effects of alcohol, making people more prone to taking risks.

Caffeine could also mask the sedative effects of alcohol, so people become less aware of how much alcohol they've drunk – a phenomenon referred to as being "wide-awake drunk". 

However, the studies included in the review varied considerably in their methods, including the lifestyle factors they took into account, such as alcohol or drug use.

This review can't quantify risks or link them with particular combinations of drink, or specific quantities.

But it does serve as a general reminder that so-called "social drinking" is not without risk, both in terms of how much alcohol is consumed and potentially making yourself vulnerable to harm.

Where did the story come from?

The study was carried out by two researchers from the Centre for Addictions Research at the University of Victoria in British Columbia, Canada.

It was funded by the Canadian Institute of Health Research. No conflicts of interest were reported by the researchers.

The study was published in the peer-reviewed Journal of Studies on Alcohol and Drugs on an open access basis, so it's free to read the study online (PDF, 208kb).

The way the study was reported, while generally accurate, in some cases made the links between risks and drinking alcohol combined with energy drinks appear to be much better established than is actually the case.

And The Sun's headline, "Bingeing on vodka Red Bull or Jagerbombs 'as bad as taking cocaine'," is an opinion, not a proven fact. 

What kind of research was this?

This systematic review aimed to examine the published literature to identify studies that have assessed the link between mixing alcohol with energy drinks and the potential risk of injury. 

The researchers say in 2007-11, 13-16% of emergency department visits in North America involved people who had drunk alcohol combined with energy drinks.

This is said to be the first review to date to look at the association. A systematic review is the best way of compiling the available literature.

However, the findings of reviews are only as good as the pooled studies included.

Studies assessing links between food and drink and health outcomes are usually observational, so they aren't able to prove cause and effect because many other factors could have had an influence.

And if the studies included in a review are very different in terms of methodology, as was the case with this review, it isn't possible to carry out a meta-analysis of the results.

This means any conclusions provided by the review carry less weight of evidence.

What did the research involve?

The reviewers searched two literature databases to identify studies published between 1981 and January 2016.

The studies included must have looked at the link between consuming alcohol mixed with energy drinks and the risk of harm or injury, and compared this with the risk from just drinking alcohol.

Energy drinks and alcohol could be either consumed in a mixed drink or separately, but on the same occasion.

A total of 13 studies met the inclusion criteria – 10 of which came from the US and Canada, and the remainder from New Zealand, Australia and Taiwan.

Eight of the studies included students – high school, college or university. They all date from 2011-15.

All of the studies were cross-sectional, mostly online surveys reviewing reports of drinking injuries.

The timeframe of alcohol or energy drink consumption was questioned ranged from the past month to the past year, while the timeframe for self-reported injuries ranged from the past month to a lifetime.

Eight of the studies asked whether injuries were actually related to drink consumption, while the other five studies just asked about reports of the two, which may not necessarily have been related.

What were the basic results?

The reviewers give an overall narrative summary of the findings.

Ten of the 13 studies reported a link between drinking alcohol and energy drinks and an increased risk of injury, though there were no consistent links with the type of injury.

Three studies didn't find this link – in fact, one study actually found the risk was higher with alcohol on its own. The researchers feel the differences could have been down to the design of the studies.

Three studies reported that when the links between the two are assessed, you need to consider risk-taking tendencies or behaviours, as well as sensation seeking.

When the researchers controlled for these variables, they still found links between alcohol and energy drinks and injury.

Most studies also controlled for general alcohol consumption or binge drinking. Two studies also controlled for drug use and one for caffeine.

Studies also reported more alcohol tended to be consumed during mixed drinking sessions than when drinking alcohol on its own.

How did the researchers interpret the results?

The researchers concluded: "There is significant need for further examination of the role of [alcohol and energy drink] use in the risk of injury.

"A better understanding of the relationship … and of the potential underlying mechanisms is crucial for informing effective preventive intervention strategies."

They go on to say the review could be used to inform the public, health professionals and policy makers of the possible risks.

Conclusion

This systematic review aimed to try to better establish whether drinking alcohol mixed with energy drinks is linked with risk of injury.

Although the majority of studies generally supported a link between consumption and increased risk of injury, as the researchers acknowledge, the high variability in the methods of the individual studies and assessment of harms "makes it difficult to determine the extent of this risk".

Nearly all the studies were online surveys that asked questions about alcohol and energy drink consumption, and self-reported injury.

But the temporal relationship between the two, and whether the drink was actually the direct cause of the reported injury, is very difficult to be sure of, especially if the timeframe of reported injuries could extend to up to a lifetime, while drink consumption was relatively recent.

For example, one of the studies was even questioning reports of injury or disease in the past year as a result of participants' work.

It's also possible confounding lifestyle factors influenced any links seen. The individual studies varied considerably in the different factors they adjusted for, such as socioeconomic factors, drug use, and normal alcohol drinking behaviours.  

The studies are also mostly representative of young student populations, and none were conducted in the UK. A link may be found if college or university students in the UK were surveyed, but we can't know this for sure.

Overall, although this study is of interest and supports a plausible theory, it can't definitively tell us whether drinking alcohol combined with energy drinks will put you at greater risk of injury or harm than if you drink alcohol alone.

But the study does reinforce the fact alcohol can be a common contributing factor to injury.

Read more about the risks associated with social drinking.