Health and fitness wearables firm Fitbit validated the ability of its wrist-worn trackers that incorporate movement and cardiac sensors to accurately determine sleep stages -- light, deep and rapid eye movements (REM), the company said in a statement on Thursday.

The results demonstrate that the recently launched devices like Fitbit Alta HR, Blaze and Charge 2 can be used to track sleep stages with a reasonable degree of accuracy in normal adult sleepers."With our sleep tracking tools, Fitbit has transformed what people can learn about their sleep habits by taking the ability to track sleep stages out of a lab and putting it on the wrist," Conor Heneghan, lead sleep research scientist at Fitbit, said in a statement.For the study, researchers tracked more than four billion nights of sleep since 2010 independently by polysomnography technicians. 

They found that while sleeping longer will lead to getting more deep and REM sleep, sleeping for seven to eight hours gives you the highest combined percentage of time in the overall sleep cycle.Further, generation Z (age 13-22) were found to sleep the most, averaging six hours and 57 minutes of sleep a night with 17 per cent of the time in deep sleep, while baby boomers (age 52-71) sleep the least at six hours and 33 minutes per night with 13 per cent of the time in deep sleep. 

The people get less deep sleep as they age, decreasing from an average of 17 per cent at age 20 to 12 per cent at age 70.Women sleep an average of 25 more minutes a night than men and have a higher percentage of REM sleep, a difference which increases even further around age 50, the researchers said.The findings will be presented at SLEEP 2017 -- the joint conference of the American Academy of Sleep Medicine and the Sleep Research Society in Boston.