They assessed the risk of cardiac events following consumption of energy drinks in patients diagnosed with congenital long QT syndrome (LQTS), a condition that affects 1 in 2000 and that can cause rapid, irregular heartbeat that can lead to sudden death.
In their study, published in the International Journal of Cardiology, they report that even small amounts of energy drinks can cause changes in the heart that can lead to life-threatening arrhythmias and recommend cautioning young patients, some of whom may still be unaware of an existing heart condition, about the danger.
The hemodynamic effects of energy drinks in healthy young adults have been assessed in prior studies with results including increased blood pressure, but no change in heart rate. This is the first study specifically designed to test the effects of these energy drinks in individuals who carry the gene faults causing congenital LQTS, say the researchers.
"The potential cardiovascular risk of energy drinks continues to emerge as an important public health issue," said lead investigator Professor Christopher Semsarian of the University of Sydney and Centenary Institute, Australia. "The population most at risk is teenagers and young adults, representing the population these drinks are most heavily marketed towards. Since energy drinks are widely available to all ages and over the counter, it is important that cardiovascular effects of these drinks are investigated."
The study was designed to assess the acute cardiovascular responses to energy drink consumption in patients with familial LQTS and to discover whether any identified cardiovascular effects correlate with changes in blood levels of the active ingredients - caffeine and taurine.
Investigators recruited 24 patients aged 16 to 50. More than half were symptomatic before diagnosis and receiving beta-blocker therapy. Most had undergone genetic testing, 13 of whom had a documented pathogenic or likely pathogenic mutation.
Participants were assigned to energy drink or control drink groups for the first study visit. The energy drink consisted of two Red Bull sugar-free cans totalling 160mg of caffeine and 2000mg of taurine, totaling 500ml. The control drink was a cordial-based 500ml drink with no caffeine or taurine.
Electrocardiograms and blood pressure were recorded every 10 minutes, while signal-averaged electrocardiogram (SAECG) testing and repeat bloods were collected every 30 minutes for a total observation time of 90 minutes.
The results of the study show that three patients (12.5%) exhibited dangerous QT prolongation following energy drink consumption and two of the three had sharp increases in blood pressure. These patients all had a documented family history of sudden cardiac death and two of them had previously experienced severe clinical issues.
"Some individual patients may be at a higher risk," added Professor Semsarian. "We therefore suggest caution in allowing the consumption of energy drinks in young patients with LQTS."
In an accompanying commentary, Professor Peter J. Schwartz, head of the Center for Cardiac Arrhythmias of Genetic Origin, IRCCS Istituto Auxologico Italiano, said: "Data suggest that the majority of LQTS patients destined to become symptomatic have the first event well after having become a teenager, which implies that a significant number of youngsters with LQTS will help themselves to energy drinks without knowing their real condition and thus endangering themselves."
The findings drew an immediate response from trade body the British Soft Drinks Association.
Gavin Partington, its director general, said: “Undoubtedly anyone sensitive to caffeine should only consume it in moderation but it’s important to bear that in mind in relation to all sources. One 250ml can of energy drink typically contains about the same amount of caffeine as a cup of coffee. The recent EFSA opinion confirms the safety of energy drinks and their ingredients and therefore does not provide any scientific justification to treat energy drinks any differently to the main contributors to daily caffeine intake including tea and coffee.”