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Coffee can have many effects on sleep, physical activity levels, and heart health. Kilito Chan/Getty Images
  • Coffee is a popular beverage commonly consumed by people all over the world.
  • Researchers are still working to understand coffee’s potential health benefits and risks.
  • Data from a recent study found that drinking coffee is associated with more activity and less sleep.
  • The study also found that drinking coffee was associated with more premature ventricular contractions, which can pose health risks depending on the person and the severity.

A​ recent study published in The New England Journal of Medicine examined the impact of coffee on several areas of health, including heart arrhythmias, activity level, sleep, and blood sugar.

Researchers found that people who drank coffee took more steps on average daily but got slightly less sleep than those who did not drink coffee.

Participants who drank coffee had more premature ventricular contractions, a type of extra heartbeat. The research suggests that drinking coffee affects people differently, and people can seek help from specialists for appropriate coffee recommendations.

Coffee is a highly popular beverage around the world. This makes it a common area of interest for research. After all, if many people are drinking it, it seems like a good idea to know how it impacts health.

Some research suggests that coffee may be associated with lower mortality risk. It may also help reduce the risk of type two diabetes, obesity, and some types of cancer.

However, just because coffee poses many potential health benefits does not mean everyone should drink it. How people consume their coffee makes a difference too. Adding cream and sugar can negate some of coffee’s potential health benefits.

Dr. Chip Lavie, cardiologist and cardiac rehabilitation and prevention director at Ochsner Health, who was not involved in the study, explained to Medical News Today:

“Most studies suggest that coffee consumption is associated with better survival, less cardivascular death, lower stroke and heart failure, less chronic hypertension (whereas a very high dose of acute intake can transiently raise blood pressure), and improvements in some risk factors, such as type 2 diabetes and dyslipidemia. These benefits are mostly gathered from large observational studies.”

This particular study looked at heart rhythms, sleep, daily step counts, and blood sugar in relation to coffee consumption.

Researchers included 100 healthy adult participants in their analysis, and the study was a randomized trial. The data collection period was two weeks. Participants wore electrocardiogram (ECG) monitors to examine heart rhythms and wore Fitbit devices to track step counts and time asleep. Finally, participants also wore a continuous glucose monitor to keep track of blood sugar levels.

Participants were then assigned to either drink coffee for two days or abstain from caffeine for two days. These random assignments continued throughout the fourteen days so that no participant consumed or abstained from coffee for more than two days.

Researchers were looking to see if participants had more or less premature atrial contractions on the days they drank coffee. Premature atrial contractions (PACs) are extra heartbeats that start in the heart’s upper chambers.

While sometimes benign, study authors note that PACs may contribute to a more dangerous heart rhythm: atrial fibrillation. Researchers found that drinking coffee was not associated with more PACs. They also found that drinking coffee did not appear to impact blood sugar levels.

W​hen drinking coffee, participants took an average of about 1,000 steps more daily and got about half an hour less sleep at night.

Participants also saw about a 50% increase in premature ventricular contractions on coffee-consumption days. Premature ventricular contractions (PVCs) are a type of extra heartbeat originating in the heart’s lower chambers. However, there did not appear to be a relationship between drinking one cup of coffee and increased PVCs.

Study author Dr. Gregory Marcus, cardiologist and professor of medicine at the University of California, San Francisco, explained key findings of the study’s results:

“Both randomized assignment to consume coffee and the amount of coffee consumed were associated with more premature ventricular contractions (PVCs), substantially more steps taken, and significantly less sleep during the following evening.”

However, the results varied among participants, possibly related to how fast they metabolized the caffeine.

The study did have limitations. First, the study cannot establish a causal relationship between the factors discussed. Second, it only included a small number of participants, all of whom were healthy, limiting the generalizations of results.

Researchers also acknowledge that some results could have been from caffeine withdrawal in participants or factors related to the study not being a blinded study.

Researchers were also limited by participant adherence to instructions and the study’s methods.

For example, the Fitbit devices used were not clinical-grade devices, so the data collection about sleep had limited precision. It is also possible that some of the effects were related to other coffee ingredients and may not be solely attributable to caffeine.

It’s important to be cautious when interpreting these results. They don’t indicate that coffee is overall dangerous or that people should stop drinking it. Rather, the study authors wrote, “These findings suggest that an individualized approach to coffee consumption may be the most appropriate method for determining the effects on health.”

PVCs can be dangerous but are also typically benign.

“Although PVCs are considered more important than PACs, they are fairly benign as well, especially if there is no underlying severe heart disease and unless they are bothersome to patients, but this is generally only the case when extremely frequent, much more so than the very minor increase noted with more coffee.”
— Dr. Chip Lavie

D​r. Marcus also noted that PVCs might increase some people’s heart failure risk.

“Our data reveal complex and variable effects, which themselves are heterogenous from individual to individual, so my hope is that people will utilize this information to tailor their own coffee consumption to best fit their own propensities and health goals,” he explained.

Dr. Ahmad Iqbal, an interventional cardiologist with Memorial Hermann, also offered the following insight:

“If there is a significant enough burden of typically benign arrhythmias (such as PACs/PVCs), it can cause other issues such as atrial fibrillation or even heart failure.”

“If one is having symptoms in the setting of heavy coffee consumption, it is advised to decrease intake and seek cardiology consultation. [T]his study is not designed to derive long-term conclusions but rather generate more hypotheses that may eventually help understand significant CV [cardiovascular] outcomes and mortality related to coffee consumption.”
— Dr. Ahmad Iqbal