The timing of our sleep is more important than previously thought, according to a new study that suggests it affects our sleep quality.

Shifting mice from their habitual sleep-wake schedule saw them get a poorer quality of sleep, even if they slept for enough time.

The shift also disrupted their immune response, leaving them susceptible to sickness, according to the US study that was published in the journal Brain, Behavior and Immunity.

The study has implications for modern society, where nighttime lighting, lengthening work days, shift work, jet lag and computer screens are thought to be responsible for throwing off the sleep-wake cycle.

Studying sleep deprivation and circadian rhythms -- the scientific term for the sleep-wake cycle -- together is no simple feat because one normally affects the other, yet the research team managed to construct a model in which total sleep time stayed the same.

Working with mice whose body clocks spawn approximately 24 hours, imitating that of our own, the researchers boxed in their day to just 20 hours, forcing their body clocks out of sync as nights descended early and mornings appeared late.

Four weeks later, the mice were injected with lipopolysaccharide, a substance that can bring on non-contagious sickness.

The unsettled mice demonstrated either blunted or overactive immune responses, implying their ability to fight illness had been thwarted.

The study attributes this to the change in circadian pattern, as the mice were getting the same number of hours on the 20-hour cycle as they had been on the 24-hour cycle.

It's a question of sleep quality, according to the study, because the mice woke often and their brain activity related to restorative sleep was reduced, according to the study.

The volatile immune responses indicate that an interruption in the sleep-wake cycle could have serious consequences for the health of any organism, according to the study.

"Just like you have a car that you're running into the ground -- things don't work right but you keep driving it until it stops," says study author Ilia Karatsoreos, an assistant professor at Washington State University. "That's what could happen if you think of disruption going on for years for somebody who's working shift work."