Caffeine linked to less sleep but deeper rest, study finds

Regular caffeine consumption may affect sleep in a way that is more complex than previously thought. People who consume four or more caffeinated beverages a day tend to sleep less than those who drink three or fewer, but their sleep may also be deeper, according to a study cited by PsyPost.

Caffeine’s effects on sleep have long been of scientific interest because adequate sleep is essential for key functions including memory, the immune system and cardiovascular health. Previous research has shown that caffeine can make it harder to fall asleep and can affect sleep duration, but its impact on sleep quality has remained less clear.

The study, published in the Journal of Psychopharmacology, sought to estimate the causal effect of habitual caffeine consumption on sleep. Researchers analyzed data from the UK Biobank and the Swiss HypnoLaus cohort, examining genetic variants associated with caffeine consumption and various measures of sleep.

The researchers also considered how many cups of caffeinated beverages participants consumed each day, along with sleep characteristics such as total sleep duration and the amount of time needed to fall asleep.

The findings showed that higher caffeine consumption did not change how people perceived their sleep or whether they considered themselves more active in the morning or at night.

Less sleep, but deeper

The study found that drinking four or more caffeinated beverages a day was associated with a reduction of between 11 and 13 minutes of sleep per night.

However, although total sleep time was shorter, sleep appeared to be deeper during the non-REM phase, as reflected by increased delta activity, a marker of more intense sleep.

The researchers concluded that high, habitual caffeine consumption alters certain sleep characteristics in the general population, while the body appears to compensate in an effort to maintain some balance.

In other words, people who consume more caffeine may sleep less overall, but some of the lost sleep time could be offset by deeper sleep.