Anyone who has felt sluggish at work after a sleepless night or who has struggled with jet lag after a long flight can take comfort in knowing he or she is not alone.
A study on biological sleep clocks by researchers at Boston's Brigham and Women's Hospital, published in The Journal of Vision, found that the longer someone is awake while they are sleep-deprived, the slower their productivity becomes.
The study tested participants under conditions of sleep deprivation on activities such as finding information quickly and accurately on computer monitors, to determine how the lack of sleep affected their response time.
As participants were awake longer and their level of deprivation grew, their ability to find the information slowed, the researchers said.
Declining ability was also noticeable during biological night time, from midnight to 6 a.m.
"The longer someone is awake, the more the ability to perform a task, in this case a visual search, is hindered, and this impact of being awake is even stronger at night," said Jeanne Duffy, an associate neuroscientist at Brigham and Women's and senior author of the study.
Researchers collected and analyzed data from 12 participants whose sleep was reduced over a month-long period.
For three weeks, participants were placed on 28-hour days with six hours of sleep, which gave them an average of 5.6 hours of sleep per night and mirrored the effects of chronic jet lag.
Another finding, Duffy said, was that getting low amounts of sleep regularly creates a progressively negative change in performance over time.
The research showed that during the first week of sleep deprivation, test speed only slowed about a second; by the third week of deprivation, it slowed by twice that.
The study did not find that accuracy declined with less sleep, but Duffy said prior studies had found time of day influences it; the later it gets, the more mistakes.
