Coffee and Atrial fibrillation ☕️
Caffeine is the active ingredient in coffee (and tea) that is responsible for the wakefulness effect of the drinks. Caffeine molecules block 'adenosine' receptors in your brain that activate for sleepiness and so that's why many people consume it in the morning to start their day. It's also a 'sympathomimetic' (activates your fight or flight system) makes it a 'stimulant' drug and so it is a common recommendation from healthcare professionals to people experiencing palpitations, or with known AF, to completely eliminate caffeine from their diet in order to try and prevent these episode.
But is this an evidence-based recommendation? And how strong is the relationship between AF risk and caffeine?
We know that at very high concentrations, it can be very dangerous. There are tragic, rare anecdotes of individuals accidentally consuming industrial-grade quantities of caffeine with fatal outcomes due to intractable arrhythmias (ventricular arrhythmias rather than AF in these case). Extrapolating from animal models and these tragic stories, this is more than the amount of caffeine in 10-20 coffees consumed at once.
What about the consumption of a more typical amount of caffeine? Are there consequences to drinking a daily cup of coffee or tea? Observational studies (once where you just monitor aspects of individual's characteristics, treatments or behaviour without affecting them) of hundreds of thousands of individuals have suggested that habitual coffee drinkers (~1-3 cups) have a lower incidence of AF than non-drinkers.🤯 This finding should be taken with a pinch of salt (or sugar 😉) because it may be that habitual coffee drinkers tend to have otherwise healthier lifestyles or be doing something different that reduces their AF risk rather than the caffeine itself.
A team of Harvard researchers asked physicians to report their coffee intake and whether they had AF or not (reference below). Almost 20,000 doctors replied and the data showed a really interesting U-shaped curve, in keeping with the trend that people who drink habitual amounts of coffee may be at lower risk of AF.
This really comes down to quality of life. Treating AF and reducing episodes of AF is largely done to improve symptoms and make patients feel better. If cutting out caffeine is not a big deal for you, go ahead and try it to see how you feel. Alternatively, if you find joy in that morning cup of coffee then there isn't the evidence to clearly say it's doing you any harm (in fact it may overall be associated with health benefits) and so don't feel obliged to make this change.
Again a couple of my favourite papers on this topic are below.
Voskoboinik A, Kalman JM, Kistler PM. Caffeine and Arrhythmias: Time to Grind the Data. JACC Clin Electrophysiol. 2018 Apr;4(4):425-432. doi: 10.1016/j.jacep.2018.01.012. PMID: 30067480.
Bodar V, Chen J, Gaziano JM, Albert C, Djoussé L. Coffee Consumption and Risk of Atrial Fibrillation in the Physicians' Health Study. J Am Heart Assoc. 2019 Aug 6;8(15):e011346. doi: 10.1161/JAHA.118.011346. Epub 2019 Aug 5. PMID: 31378120; PMCID: PMC6761675.