Am I brave enough to quaff my beloved and much-missed shot on the strength of 200 randomised patients? I think not, doctor.
I stopped drinking coffee 35 years ago when an annoying occasional trippy heartbeat I’d had since I was teenager turned into a full-on bout of atrial fibrillation that landed me in hospital for the first time.
At the time I was a 10-15 cup-a-day drinker, not because I particularly liked coffee – nobody could “like” the swill News Corp provided in their newsroom kitchens back then – but because it was a good excuse to get up and away from the sports desk whenever I couldn’t think of a word, or when the bloke sports journos got a little too bloke-sports-journo-ish. Ten to 15 times a day.
My doctor said stop drinking coffee, take this tablet forever and you’ll be fine (he was wrong).
So, I stopped drinking coffee cold turkey – the second-worst four days of my life. The worst four days was when my parents stopped smoking cold turkey when I was 10. They were grumpy, readers.
Decades, a metric tonne of medication and one successful ablation later, I still miss coffee (and coffee ice-cream) but not a drop has crossed my lips.
Imagine then my reaction when a new study out of the University of California San Francisco, the University of Adelaide and the University of Toronto came across my desk, announcing that I could have been having a cup of joe a day for the past 35 years, and not only would I not be dead, I might even have been BETTER OFF!!
This study took 200 current or previous (within past five years) coffee-drinking adults with persistent AF, or atrial flutter with a history of AF, planned for electrical cardioversion from five hospitals in the US, Canada, and Australia between November 2021 and December 2024 and randomised into two even groups.
Half were encouraged to drink at least one cup of caffeinated coffee daily for six months. Patients in the abstinence group were encouraged to completely abstain from both caffeinated and decaffeinated coffee and other caffeine-containing products for six months.
My gut and my doctors say the non-coffee drinkers will have less AF, right?
Yeah, nah.
“AF or atrial flutter recurrence was less in the coffee consumption (47%) than the coffee abstinence (64%) group, resulting in a 39% lower hazard of recurrence (hazard ratio, 0.61 [95% CI, 0.42-0.89]; P = .01),” found the researchers.
“A comparable benefit of coffee consumption was observed with AF recurrence only. There was no significant difference in adverse events.”
Y’what, now?
“The current results contrast with the traditional assumption that coffee promotes atrial arrhythmogenesis, but fit with some observational data on the subject,” said the authors.
“Conventional wisdom has held that caffeinated coffee is proarrhythmic.
“In contrast, most (although not all) observational studies have suggested a neutral or beneficial association of coffee with AF.
“However, nonrandomised studies are prone to residual confounding that cannot be definitely excluded.
“The present trial, where measured and unmeasured confounders should have been balanced via randomised allocation, suggests that caffeinated coffee consumption may reduce recurrence of persistent AF compared with abstinence from coffee and other caffeinated products.
“Moreover, a continued separation of survival curves over time implies that this difference may be more attributable to a benefit of coffee consumption rather than harm from abrupt coffee cessation and withdrawal.”
The researchers said several mechanisms could be at play.
“Caffeine concentrations associated with typical coffee consumption result in blockade of A1 and A2a adenosine receptors,” they said. “Adenosine facilitates AF induction, an effect thought to be due to sympathoexcitatory effects, shortening of atrial refractoriness, and ectopic triggers. Caffeine may thus have adenosine-mediated antiarrhythmic properties.”
Another theory is that coffee also appears to have anti-inflammatory properties.
“As systemic inflammation is an AF risk factor, coffee might reduce AF risk by decreasing inflammation.
“AF can be vagally mediated, and perhaps the catecholaminergic effects of caffeine are therefore protective.
“Caffeine is also a diuretic, potentially reducing blood pressure and AF risk.”
The researchers did acknowledge eight limitations to their study:
- there was no protocol-mandated AF detection method or schedule;
- the sample size was modest;
- there were some numeric imbalances in baseline characteristics;
- participants were not blinded to the exposure;
- only a minority of screened patients were willing to participate;
- paroxysmal AF may not respond in the same manner as persistent AF to coffee and requires further study;
- adherence in the abstinence group was suboptimal; and
- while no significant differences in adverse events were observed, this trial was not specifically powered to detect a difference in these less common events.
Given all of that, and the fact every doctor EVER told me coffee makes AF worse, I’m not sure I’m ever going to be brave enough to do more than sniff my partner’s espresso shot.
I wish it weren’t so.
Send your double shot macchiato story ideas to holly@medicalrepublic.com.au
