A new study published in the European Heart Journal on Wednesday found that people who drink coffee in the morning have a lower risk of dying from cardiovascular disease compared to those who consume coffee throughout the day. The research, led by Dr. Lu Qi from Tulane University, also indicated that morning coffee drinkers have a lower overall mortality risk compared to non-coffee drinkers.
"This is the first study testing coffee drinking timing patterns and health outcomes," said Dr. Lu Qi, HCA Regents Distinguished Chair and Professor at the Celia Scott Weatherhead School of Public Health and Tropical Medicine at Tulane University, New Orleans, USA. "Our findings indicate that it's not just whether you drink coffee or how much you drink, but the time of day when you drink coffee that's important."
The study analyzed data from 40,725 adults participating in the US National Health and Nutrition Examination Survey (NHANES) between 1999 and 2018. Participants were asked about all the food and drink they consumed on at least one day, including whether they drank coffee, how much, and when. A sub-group of 1,463 people completed a detailed food and drink diary for a full week.
Researchers linked the participants' information with records of deaths and causes of death over a period of nine to ten years. They found that around 36% of people in the study were morning coffee drinkers, primarily consuming coffee before midday. About 16% drank coffee throughout the day—morning, afternoon, and evening—while approximately 48% did not drink coffee at all.
Compared with people who did not drink coffee, morning coffee drinkers were 16% less likely to die of any cause and 31% less likely to die of cardiovascular disease. There was no reduction in risk for all-day coffee drinkers compared to non-coffee drinkers. Morning coffee drinkers benefited from lower risks whether they were moderate drinkers (two to three cups) or heavy drinkers (more than three cups). Light morning drinkers (one cup or less) saw a smaller decrease in risk.
"This study doesn't tell us why drinking coffee in the morning reduces the risk of death from cardiovascular disease," added Dr. Lu Qi. "A possible explanation is that consuming coffee in the afternoon or evening may disrupt circadian rhythms and levels of hormones such as melatonin. This, in turn, leads to changes in cardiovascular risk factors such as inflammation and blood pressure."
In an accompanying editorial, Professor Thomas F. Lüschner from Royal Brompton and Harefield Hospitals, London, UK, commented on the significance of the findings. "During a median follow-up of almost a decade, and after adjustment for caffeinated and decaffeinated coffee intake, the amounts of cups per day, sleep hours, and other confounders, the morning-type, rather than the all-day-type pattern, was significantly associated with lower risks of all-cause mortality with a hazard ratio of 0.84 and of cardiovascular mortality of even 0.69 as compared with non-coffee drinkers," he stated.
"Why would time of the day matter? In the morning hours there is commonly a marked increase in sympathetic activity as we wake up and get out of bed, an effect that fades away during the day and reaches its lowest level during sleep," Professor Lüschner explained. "Thus, it is possible, as the authors point out, that coffee drinking in the afternoon or evening disrupts the circadian rhythm of sympathetic activity. Indeed, many all-day drinkers suffer from sleep disturbances."
Professor Lüschner concluded with practical advice based on the study's results: "Overall, we must accept the now substantial evidence that coffee drinking, particularly in the morning hours, is likely to be healthy. Thus, drink your coffee, but do so in the morning!"
The article was written with the assistance of a news analysis system.