How do alcohol and caffeine affect sleep?

  • Researchers consider insufficient sleep to be an unrecognized worldwide health issue.
  • People who have sleep issues commonly use caffeine during the day to stay awake and alcohol at night to help them sleep.
  • Researchers from the University of Washington School of Medicine found people who use both substances did not perceive a reduction in their sleep quality.
  • Scientists believe this false perception may lead to a habitual self-medicating cycle that people do not realize, leading to poor sleep.

Insufficient sleep is considered by researchers to be an unrecognized global health concern.

Past studies show around one third of the world’s population is affected by insomnia symptoms. And as many as 70 million Americans have a sleep disorder.

People who find themselves tired during the day from poor sleep commonly drink caffeinated beverages during the day to help them stay awake.

These same people may also drink alcohol at night to help them sleep.

Now, a new study published in the journal PLOS ONE is the first known to take a look at how the use of both substances — caffeine and alcohol — affect overall sleep.

Researchers from the University of Washington School of Medicine found study participants who used caffeine during the day and alcohol at night did not perceive a reduction in their sleep quality, despite the substances reducing perceived sleep quality when studied individually.

Scientists believe this false perception may lead to a habitual self-medicating cycle that people do not realize, leading to poor sleep.

Caffeine, alcohol, and sleep: What we know so far

According to Frank Song, a researcher and fourth-year clinical psychology doctoral candidate in the Department of Psychiatry and Behavioral Sciences at the University of Washington School of Medicine and lead author of this study, even though prior research has taught people the negative effects of caffeine, and separately, alcohol on sleep, there had not been a study looking into how the two substances together affect sleep as individuals go about their lives.

In regards to alcohol use, a study published in October 2021 found a higher alcohol consumption was associated with poorer sleep quality and shorter sleep duration.

Research published in December 2019 reported alcohol disrupts sleep in several ways, including contributing to abnormalities of circadian rhythms and increasing breathing-related sleep issues.

When it comes to daytime use of caffeine, a study published in September 2023 discovered caffeine can delay the onset of REM sleep.

And while caffeine may help a person feel and stay awake during the day, past studies show its continued use can harm overall sleep quality.

Each cup of caffeine reduces sleep quantity by 10 minutes

For this study, Song and his team used digital daily surveying tools to measure the alcohol and caffeine consumption habits and sleep-related measures of 17 male, full-time financial traders over six weeks.

“We chose to target financial traders because this is an adult population that consumes both caffeine and alcohol regularly, which we know both from research and my experience — I was an investment analyst on Wall Street so I worked alongside many traders,” Song told Medical News Today.

“Also, their profession requires high attention and cognitive speed, and so they value alertness and mental acuity during the day, which I think represents the lifestyles of many working adults,” he said.

When analyzed individually, researchers found caffeine use reduced study participants’ reported sleep quantity by 10 minutes per cup consumed the previous day on average.

“We had predicted we would indeed find a caffeine-induced decrease in sleep duration based on prior research on caffeine and sleep,” Song said. “We were surprised by the magnitude of the reduction — it was larger than we had expected.”

They also found participants who drank alcohol the day before self-reported a 3% decrease in their sleep quality per drink on average.

“We had also predicted this decline based on what we learned from prior research on alcohol and sleep so this made sense to us,” Song commented.

Habitual stimulant use may hide sleep quality decline

When researchers looked at how both caffeine and alcohol use affected study participants’ perceived sleep quality, the results were a bit different.

“It is difficult to quantify the interaction the same way we interpret the separate effects of caffeine and alcohol on sleep quantity/quality,” Song explained.

“That being said, we found an intriguing interaction where the sedating effects of evening alcohol consumption mitigated some of the detrimental impact of daytime caffeine consumption on sleep,” he pointed out.

However, Song and his team found that the habitual use of alcohol to overcome the stimulant effects of caffeine and vice versa suggests a form of self-medication behavior among study participants.

“Despite caffeine leading to reduced sleep quantity, individuals did not perceive a reduction in sleep quality, suggesting a mismatch in perception. This may contribute to continued self-medicating despite its negative effects on sleep. In other words, habitual use of the two substances could mask the decline in sleep quality, leaving the individual unaware of their poor sleep.”
— Frank Song, lead author

Why self-medicating with alcohol, caffeine hurts sleep

After reviewing this study, Dr. John Saito, a pulmonologist at the Children’s Hospital of Orange County and a member of the American Academy of Sleep Medicine Public Awareness Advisory Committee, told MNT he was not surprised by these findings.

“As a sedative, alcohol is a neurotoxin that depresses our central nervous system and reduces our awareness of our surroundings,” Dr. Saito explained.

“Sedation is not sleep. As stated, alcohol consumption prior to sleep significantly disrupts normal restorative sleep. As a stimulant, caffeine increases alertness by blocking our brain’s perception of sleepiness and thus has been shown to reduce our sleep duration.”
— Dr. John Saito

“In the short term, taking chemicals for symptomatic relief is not new and thus, the observation that taking both caffeine and alcohol together altered perception of sleep quality was not surprising. Just like banging your head against the wall daily and taking cannabis and reporting that pain was not as severe as expected,” he said.

MNT also spoke with Dr. Monique May, a board certified family physician and medical advisor for Aeroflow Sleep, about this study.

Dr. May said doctors could use this data to warn their patients about the slippery slope of self-medication.

“There is the potential for people to need more of either substance to balance themselves out, and that could become problematic given the addictive risk of alcohol,” she explained.

“[People] should be aware that alcohol tends to negatively affect the quality of sleep while caffeine negatively affects the quantity of sleep.”
— Dr. Monique May

“It is also important to point out that in the study there was also a small effect on sleep quality caused by caffeine, but to a lesser extent than that on sleep quantity. This ‘mismatch in perception between sleep quantity and sleep quality’ may explain why people still use caffeine despite its harmful effects on sleep,” Dr. May added.

Source: Read Full Article