Q: My smartwatch shows me that my sleeping heart rate is much higher at night after I've had a couple of glasses of wine. It's normally around 60 beats per minute, but it spikes up to 80 to 100 if I drink more than a glass of wine.
Is that normal?
A: We all know that a glass or two of wine can help you relax and unwind. But alcohol can also have pronounced effects on your cardiovascular system in the hours after you consume it, causing your heart to beat faster, at least in the short term. And in general, the more you drink, the greater the uptick in your heart rate.
Experts say that for most healthy adults, a temporary increase in heart rate caused by one or two drinks is probably nothing to worry about. But it could be problematic for people who have conditions that cause irregular heart rhythms, such as atrial fibrillation or other types of arrhythmia, or for those who are at high risk for heart attacks or strokes.
Last year, a group of researchers analyzed data from 32 different clinical trials of alcohol consumption involving 767 people; most were healthy young men in their 20s and 30s. They saw distinct patterns in how alcohol affected their heart rates and blood pressure readings shortly after drinking.
In general, a normal resting heart rate for adults is between 60 and 100 beats per minute. The researchers found that consuming one standard drink — generally defined as a 12-ounce beer, a 5-ounce glass of wine or a cocktail containing 1.5 ounces of liquor — tended to elevate the participants' heart rates by about five beats per minute in the six hours that followed. With two or more drinks, the increase in heart rate was greater, and heart rates remained slightly elevated up to 24 hours later.
Alcohol also had distinct effects on blood pressure. A single drink had little effect on blood pressure, but when people consumed two drinks, they experienced a slight dip in their blood pressure levels in the hours that followed. When they had more than two drinks, however, they saw their blood pressure levels fall at first and then begin to climb, eventually becoming slightly elevated about 13 hours after they drank. The findings on blood pressure seem to square with other studies that have shown that light drinking can be slightly beneficial to cardiovascular health, causing your blood vessels to dilate and blood pressure to fall, but that having more than two drinks on one occasion can stress your circulation.
It's common for people to drink in the evening. So scientists have also looked at what happens when people consume alcohol before going to bed.
In one study published in January, researchers recruited 26 men and women and had them spend three nights in a lab where they were monitored as they slept.
◼️ On one occasion, the participants consumed what are considered "moderate" amounts of alcohol before going to bed: The women each had one glass of wine, and the men drank two glasses of wine.
◼️ On another night, the participants drank heavier amounts: The women drank three glasses of wine, and the men had four.
◼️ On the third night, they were all given nonalcoholic wine, which served as a placebo.
The researchers found that when people drank moderate amounts of wine, their nighttime heart rates rose by 4% compared with when they did not drink alcohol. But their heart rates returned to normal in the morning hours.
When people drank heavier amounts, however, their nighttime heart rates spiked 14% and remained elevated into the morning. The study also found that alcohol, especially when consumed in higher amounts, temporarily lowered the participants' heart rate variability, a measure of the variation in time between heartbeats. A higher variability is generally a sign of better cardiovascular fitness.
One particularly striking study published in 2017 looked at how alcohol could affect your heart rate in social settings. The study was carried out at the Munich Oktoberfest, the world's largest public beer festival. The researchers recruited more than 3,000 men and women who had been drinking but were not legally impaired.
They tested the festivalgoers' blood alcohol concentrations and gave them EKGs to assess their cardiac function. The researchers found that about 26% of the revelers had a resting heart rate above 100 beats per minute, a risky but not life-threatening condition known as sinus tachycardia.
Meanwhile, 5% to 6% of the participants showed other types of irregular heartbeats that are considered more dangerous, including atrial fibrillation, which can lead to serious complications such as strokes. The higher the participants' breath alcohol concentrations, the greater their odds of having one of these irregular heart rhythms.
Dr. Stefan Brunner, a cardiologist at the University Hospital of Munich and an author of the study, said his findings demonstrated that in general, heart rate climbs continuously with increasing blood alcohol levels, but not everyone shows the same level of susceptibility.
"Some people react more profoundly with an increasing heart rate than others," he said, though it's unclear why that is. Some people may simply have a higher tolerance for alcohol, he said.
Brunner emphasized that for most healthy adults, an increase in heart rate in response to alcohol should not be alarming, especially if you are drinking in moderation, which the Dietary Guidelines for Americans defines as no more than one drink a day for women and up to two drinks per day for men.
"An increase in heart rate from 60 to 80 to 100 beats per minute is not of concern and just reflects the influence of alcohol," Brunner said, though he added that you should be concerned if you experience palpitations after drinking or if your smartwatch alerts you to an abnormal heart rhythm such as atrial fibrillation.
Also, drinkers should be cautious if they have strong risk factors for developing a heart rhythm disorder, such as high blood pressure or coronary artery disease, or if they have experienced arrhythmia in the past. One recent trial published in the Annals of Internal Medicine found that just one can of beer or a single glass of wine could cause an episode of atrial fibrillation in people who have a history of the condition.
Dr. Peter Kistler, a cardiologist and expert on heart rhythm disorders, said that people with arrhythmia can drink alcohol, but that they should do so only occasionally, limiting themselves to just one standard drink no more than three or four times a week.
Avoiding alcohol altogether, however, could make a big difference. Kistler's research has shown that in people with recurrent arrhythmia who were regular drinkers, giving up alcohol cut their rate of events in half.