According to research conducted by Seoul University in South Korea, drinking two cups a day for more than 30 years can shrink the part of the brain responsible for sleep control.
Recruiting 162 healthy but elderly participants, scientists explored their coffee habits and how much shut eye they managed.
In their investigation, they assessed the volunteers with MRI brain scans of their pineal gland - the part of the brain that releases the hormone melatonin which tells the body when it's time to sleep.
The scans revealed moderate to heavy drinkers - more than two cups a day - had 20 per cent smaller glands than those who don't drink.
Researchers say that long-term consumption may be the cause for shrinkage leading to chronic insomnia. However, experts also note that the type of coffee people were drinking was not taken into account.