A warning over the health impacts of shift work, for the one in five Kiwis who regularly work shifts

New research in the Plos One journal shows shift workers are more likely to sleep fewer hours -- of poorer quality -- and to have reduced physical and mental functions.

They're also more likely to report poor health and depressive symptoms at age 50.

Sleep Well Clinic's Dr Alex Bartle says sleep is one of the three pillars of health, but what matters most is getting the right amount of sleep.

About 20 percent of Kiwis work irregular hours.