In a cohort of over 300,000 individuals, researchers have demonstrated that neither coffee consumption nor genetic variants that affect caffeine metabolism raise the risk of cardiac arrhythmia.
For many, a cup of coffee (or two) is an essential part of the day. Given its popularity, there is ongoing debate surrounding the health implications of regular coffee consumption.
Small, observational studies have sparked concern that the popular beverage increases the risk of arrhythmia (problems with heart rhythm). However, more recent studies have not replicated these findings. In fact, some of these studies have shown that drinking coffee can actually be beneficial to health, by reducing the risk of cancer, diabetes, cardiovascular disease and overall mortality.
Coffee consumption and arrhythmia risk
A recent study, published in JAMA Internal Medicine, sought to determine whether there was an association between caffeine consumption and risk of arrhythmia. Researchers at the University of California assessed a large, population-based cohort of 386,258 individuals from the UK BioBank. The participants were grouped into categories corresponding to daily coffee intake and were followed up for 4.5 years. Over this time, the participants self-reported coffee consumption and underwent physical examinations. The researchers adjusted for confounding variables, including demographic characteristics, comorbidities and lifestyle habits.
Consistent with previous studies, the results showed that there was a 3% lower risk of incident arrhythmia associated with each additional cup of habitual coffee. Nevertheless, since this was based on self-reported, observational data, there were likely other confounding variables that were not accounted for.
In observational studies, Mendelian randomisation is a powerful tool to evaluate whether a risk factor exerts genuine causal effects on an outcome. It is analogous to a randomised controlled trial. Per Mendel’s Law of Segregation, genotype is assigned randomly. Genetic variants can thereby serve as a proxy for the random assignment of clinical interventions on risk factors.
In this case, the researchers selected genetic variants previously identified to be associated with caffeine metabolism. They found a positive association between the speed of caffeine metabolism and coffee consumption. However, Mendelian randomisation analyses revealed no significant association between caffeine metabolism and arrhythmia risk. This supports the finding that coffee consumption does not heighten risk of arrhythmia.
Genomic risk variants
The study also showed that the association between coffee intake and arrhythmia risk is not altered by genetic variants involved in caffeine metabolism. This indicates that genomic polymorphisms in caffeine metabolism do not contribute to arrhythmia risk. However, this does not negate the possibility that other genomic variants may affect risk of the disease.
Ultimately, the researchers debunked claims that coffee consumption increases the risk of arrhythmia. They also found that genetic differences in caffeine metabolism do not contribute to the risk either. For coffee enthusiasts, this study is certainly grounds for another coffee break!
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