March 9, 2010 (San Francisco, California) — Good news for coffee drinkers--new observational data presented last week at EPI|PNAM 2010, the Cardiovascular Disease Epidemiology and Prevention and Nutrition, Physical Activity, and Metabolism 2010 Conference, suggests that multiple cups of Joe are associated with a lower risk of arrhythmias. 
"A lot of people think they have palpitations from coffee, and doctors commonly tell people not to drink it, but there are very few actual data, and the data that are available suggest no relationship," said lead investigator Dr Arthur Klatsky (Kaiser Permanente Division of Research, Oakland, CA). "We went into this study thinking there would be no association, but to our surprise, there was actually an inverse relationship. It could be protective, although one observational study doesn't prove anything yet."
To heartwire , Klatsky said his group has studied coffee off and on for many years and has published several studies, which have tended to vary in their results. These studies suggested a slightly increased risk of fatal and nonfatal MI, mostly in smokers, and no overall effect of coffee drinking on total mortality or cardiovascular mortality.
With these inconclusive findings, Klatsky said his group decided to look at some of the other major causes of cardiovascular disease, such as arrhythmias. They studied 130 054 participants in the Kaiser Permanente health plan, all of whom completed a questionnaire on coffee intake and other health habits.
After adjusting for multiple variables, including body-mass index, blood pressure, total cholesterol, and other measurements, the researchers found that coffee consumption was associated with a lower risk of hospitalization for arrhythmias and that the protective effect appeared to be additive. Individuals who drank more than four cups of coffee per day had an 18% lower risk of being hospitalized for any arrhythmia, and this reduction in risk was consistent among men and women, different ethnic groups, and smokers and nonsmokers.
Relative Risk (95% CI) of Arrhythmia Diagnosed by Coffee Intake
|Arrhythmia||<1 cup/d||1–3 cups/d||>4 cups/d|
|All arrhythmia||0.97 (0.85–1.11)||0.93 (0.84-1.02)||0.82 (0.73–0.93)|
|Paroxysmal supraventricular tachycardia||0.85 (0.54–1.34)||1.01 (0.72–1.40)||0.63 (0.41–0.98)|
|Paroxysmal ventricular tachycardia||0.99 (0.59–1.63)||1.04 (0.71–1.53)||1.22 (0.79–1.87)|
|Atrial fibrillation||0.82 (0.67–1.00)||0.88 (0.76–1.01)||0.81 (0.69–0.96)|
|Atrial flutter||0.99 (0.65–1.93)||0.86 (0.62–1.20)||0.80 (0.54–1.19)|
|Premature beats||1.98 (1.02–3.84)||0.98 (0.54–1.79)||0.62 (0.28–1.35)|
|SA node dysfunction||1.04 (0.71–1.52)||0.90 (0.67–1.21)||0.88 (0.62–1.24)|
|Other arrhythmia||1.02 (0.79–1.32)||0.93 (0.77–1.14)||0.72 (0.56–0.93)|
Klatsky said that coffee is a complex substance and that it includes other ingredients that might be at work, including antioxidants, in reducing the risk of arrhythmias. However, they also performed an analysis looking at the relative reductions in risk among people who drank only decaffeinated coffee and found no protective effect, which suggests caffeine is the protective source.
The mechanisms are still unknown at this stage, but Klatsky said that caffeine competes with adenosine in brain, so it might also compete with adenosine in the heart. Because adenosine affects conduction and recovery of heart muscle cells after depolarization, one of those effects, particularly the shortening of the refractory period, could provoke rhythm problems. By drinking coffee, the researchers speculate that this adverse effect is attenuated.
The data are observational and need to be confirmed in other studies. Moreover, the end point includes hospitalizations for arrhythmias, an end point that is easy to document, but future studies examining rhythm disturbances should include arrhythmias not severe enough for the patient to warrant a trip to the hospital, according to the researchers.
With the possibility of coffee protecting the heart and at minimum showing no risk of harm, Klatsky said it is possible for the popular drink to be tested in a randomized, controlled clinical trial, although the kinks of that study would need to be worked out.
"It might be a little tricky to get people to give up their coffee, and for those who aren't coffee drinkers, it might be tough to get them to start drinking four cups per day," said Klatsky.
Heartwire from Medscape © 2010 Medscape, LLC
Cite this: Coffee Associated With Lower Risk of Arrhythmias - Medscape - Mar 09, 2010.