"But on the other hand, if you are sleepy, there's only one good way to reduce the negative effects of that, which is to get some sleep ... twenty to thirty minutes will restore you back to maximum alertness but not affect your ability to get sleep at night."
Being sleepy at work isn't the same as being lazy, he said – and the consequences of being tired at work can be disastrous.
"It increases the risks of a workplace accident, motor vehicle accidents ... people who are fatigued and sleepy actually have poor health.
"They're at risk of other health problems such as hypertension, diabetes, obesity – and people who don't get enough sleep even have shorter life spans than people who get adequate amounts of sleep."
In Japan, some companies are installing soundproof pods to allow workers to get some rest, but there's still stigma around napping at work in a lot of places - a US government directive ordered by the General Service Administration has banned sleeping in the office, the BBC reports.
But Epstein says that at a time when a lot of people in the workforce are doing shift work or odd hours, they're going to struggle with fatigue.
He says the best way to deal with this is for the workplace to have a fatigue management program, including educating workers about the need for sleep, making sure they're rested enough to do their job, and providing the opportunity to nap if the workers are tired.
The US Centers for Disease Control and Prevention recently recommended that employers enforce a fatigue management program for their workers.
