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If you love coffee, enjoy it—but remember timing matters for both sleep and health.
According to Statista, 60 percent of people are satisfied with one cup of coffee a day, while some coffee enthusiasts drink eight or more.
Newsweek spoke with sleep expert Dr. David Benavides of Harvard Medical School and Brigham and Women’s Hospital. His team’s research found that consuming caffeine up to six hours before bedtime can significantly disrupt sleep and reduce sleep quality.
The Science of Caffeine and Sleep
So, why does caffeine interfere with sleep? Dr. Benavides explained, “Caffeine blocks adenosine—a chemical in the brain that helps us fall asleep. Throughout the day, we naturally accumulate more of this substance, which makes us feel sleepy. Blocking this process with caffeine can lead to increased energy at the expense of sleep.”
A recent study found that late caffeine consumption not only shortens sleep but also reduces deep sleep, which is crucial for many restorative processes.
Dr. Benavides said morning coffee doesn’t harm sleep and may even offer health benefits. Another study by researchers at several U.S. universities looked at how coffee habits affect heart health and longevity.
They analyzed data from more than 40,000 American adults in the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2018. They identified two common patterns: 36 percent mainly drank coffee in the morning, while 14 percent drank it throughout the day.
After nearly a decade they tracked deaths from all causes, including heart disease and cancer. People who primarily drank coffee in the morning had a lower risk of death from any cause and from heart disease than non-drinkers.
However, drinking coffee throughout the day did not provide the same protective effects.
Caffeine Half-Life and Individual Differences
Dr. Benavides also emphasized the importance of understanding caffeine metabolism and its half-life—the time it takes for the body to eliminate half of the substance.
He said, “It’s important to consider that the half-life of caffeine is about 5-6 hours. So, if you drink a cup of coffee at 3 PM, half of the caffeine may still be in your system until 8-9 PM. This process can be further complicated by genetics, as some people naturally metabolize caffeine faster, while others do so more slowly.”
Moderate Caffeine Intake is Beneficial
While caffeine can disrupt sleep, it doesn’t deserve a bad reputation. In moderation, coffee can enhance daily life and offer benefits without compromising sleep quality.
If you feel fatigued despite getting enough sleep, Dr. Benavides recommends seeing a doctor to rule out health issues.
