Feeling groggy on Monday morning? That might be because you haven't been allowing yourself enough quality time in bed.

The National Sleep Foundation has published new sleeping guidelines based on a study of 320 research articles, with different amounts recommended for each age group.

The time needed for a fully restorative sleep declines as one ages, ranging from 14-17 hours as a newborn to 7-8 in the 65+ age category.

Teenagers, whose sleep natural pattern tends towards late nights and late rises, need 8-10 hours; while 7-9 hours is best for adults.

The study also emphasises that over-sleeping can come with the same downsides as under-sleeping, and that 'catching up' on the weekend is no replacement for missed sleep.

Quality of sleep was not considered for the study, but could have an effect of the amount of sleep required. Quality can vary depending on whether a person wakes up during the night, or how much REM sleep they have.

Don Carlos, a professor in the Loyola University Chicago Stritch School of Medicine, explains the need for continued research on the topic of sleep:

"We still have a great deal to learn about the function of sleep... But we don't know the details of what the function of sleep is, even though it is how we spend one-third of our lives."

Hat-tip to the Guardian.