"I was in a daze[1] . I don't know what I was thinking about and the next thing I know I was hitting the brakes."


Those were William Rockefeller's words to a law enforcement source, the New York Daily News reports, as investigators examine the moments leading up to the Metro North train derailment in the Bronx on Sunday that killed four and injured 75.


Unlike previously reported, Rockefeller seems to have been well-rested, officials say. "There's every indication that he would have had time to get full restorative sleep[2] ," Earl Weener of the National Transportation Safety Board told the Daily News.


While zoned out, it's been suggested[3] that Rockefeller may have slipped into what's known as microsleep[4] , when you nod off for just a few seconds, often without even knowing you're doing so. People in microsleep might even still have their eyes open, or still carry out tasks "as if on a kind of auto-pilot," ABC News reported.


That's because during a microsleep, parts of the brain remain alert and awake while others doze off, according to a 2011 study in rats. Specific nerve cells in the brain entered a sleep-like state[5] , according to the study, "with negative consequences on performance."


When sleep doctors look at a brain at rest during a sleep study, they look at the activity in 30-second chunks, Dr. W. Christopher Winter, M.D., medical director at the Martha Jefferson Sleep Center in Charlottesville, Va., tells HuffPost Healthy Living. "Sleep scientists define sleep onset as the first time you have 15 seconds of sleep within a 30-second period," he says. "It's not that the lights just cut off, the light flickers and flickers and then it's off." During that flickering, we might have microsleeps of a few seconds, while during the larger 30-second period we are technically awake.


But we're generally not aware it's happening, he explains. Someone driving or doing another monotonous task may suddenly notice they weren't all there for a brief moment, a realization that's often startling, says Winter, who has not evaluated Rockefeller.



Microsleep is evidence of how powerful our urge to sleep is, Dr. Charles Czeisler, M.D., Ph.D.[6] , director of the Division of Sleep Medicine at Harvard Medical School, told ABC News. "We often delude ourselves into thinking that we decide whether or not we're going to go to sleep," he said. "'I'm just going to go another 10 miles. It's only half an hour to my house.' When you build up enough sleep pressure, you automatically make that transition to go to sleep. It can happen in the blink of an eye."


Unfortunately, those few seconds of unconsciousness can be long enough to wreak havoc. A car traveling 55 miles per hour will cover the length of an entire football field in just 4.6 seconds[7] , the average amount of time distracted drivers spend reading or sending texts, according to the National Highway Traffic Safety Administration. To be asleep for the same period of time -- or even less -- could spell disaster.


While it can happen to anyone, says Winter, it would be unusual for a well-rested person who just got behind the wheel to experience a microsleep. "The people who are most susceptible are people who are sleep deprived and people who are in a monotonous situation for longer periods of time," he says.



Also on HuffPost:




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  • Hurts Your Sleep


    A study of police officers found a strong link between working the night or evening shift, and <a href="http://www.huffingtonpost.com/2012/07/21/police-sleep-shift-work-_n_1686727.html">getting fewer than six hours of sleep</a> a day. The research, published in the journal <em>Workplace Health & Safety</em>, also showed that police officers who got fewer than six hours of sleep a day had more than a <a href="http://www.huffingtonpost.com/2012/07/21/police-sleep-shift-work-_n_1686727.html">doubled risk of bad quality sleep</a>, compared with those who got six or more hours of sleep a day. And in another study in the journal <em>SLEEP</em>, University of Buenos Aires researchers found that shift workers were more likely to experience <a href="http://www.cbc.ca/news/health/story/2007/08/02/serotonin-shift.html">lower serotonin levels</a> than non shift workers, which could thereby impact sleep, CBC reported. Serotonin, the "feel-good hormone," is also known to impact sleep.




  • Raises Breast Cancer Risk


    Working the night shift raises <a href="http://www.huffingtonpost.com/2012/07/01/shift-work-breast-cancer-night-sleep_n_1612486.html">a woman's risk of breast cancer</a> risk by 30 percent, according to a study in the <em>International Journal of Cancer</em>. Specifically, French researchers found that the breast cancer risk of women who <a href="http://www.huffingtonpost.com/2012/07/01/shift-work-breast-cancer-night-sleep_n_1612486.html">worked the night shift</a> for four years was <em>especially</em> clear, as well as those who only worked the night shift for three or fewer nights a week (meaning their daily rhythms were disturbed more often).




  • Raises Obesity And Diabetes Risks


    Sleeping too little or sleeping "against" your body's natural biological clock could increase the likelihood of <a href="http://www.huffingtonpost.com/2012/04/11/shift-work-sleep-type-2-diabetes-obesity_n_1418394.html">developing diabetes or becoming obese</a>, according to a study from Brigham and Women's Hospital researchers in the journal <em>Science Translational Medicine</em>. While the study was small -- it only included 21 people! -- the findings are valuable because it was a controlled study, meaning it placed people in an environment where scientists decided how much sleep they got each day, and what time they were able to go to sleep. "Since night workers often have a hard time sleeping during the day, they can face both <a href="http://www.eurekalert.org/pub_releases/2012-04/bawh-lsd040612.php">circadian disruption</a> working at night and insufficient sleep during the day," study researcher Orfeo M. Buxton, Ph.D., a neuroscientist at Brigham and Women's Hospital, said in a statement. "The evidence is clear that getting enough sleep is important for health, and that sleep should be at night for best effect." Plus, another study in the journal <em>PLoS Medicine</em> showed that rotating shift workers had a <a href="http://healthland.time.com/2011/12/07/why-working-the-night-shift-may-boost-your-risk-of-diabetes/">higher Type 2 diabetes risk</a>, likely because of shift work's impact on insulin activity, <em>TIME</em> reported.




  • Increases Heart Attack Risk


    Working the night shift could make you more likely to <a href="http://www.huffingtonpost.ca/2012/07/26/shift-work-heart-health_n_1708093.html?utm_hp_ref=health-news&ir=Health%20News&ncid=edlinkusaolp00000008">have a heart attack</a>, according to a review of research published in the <em>British Medical Journal</em>. The review included 34 studies, and showed that working the night shift could account for <a href="http://www.huffingtonpost.ca/2012/07/26/shift-work-heart-health_n_1708093.html?utm_hp_ref=health-news&ir=Health%20News&ncid=edlinkusaolp00000008">7 percent of heart attacks</a> that occurred in 2009 and 2010 in Canada, as well as 1.6 percent of ischemic strokes and 7.3 percent of coronary events during that time period, CBC reported.




  • Provokes Negative Metabolic Changes


    Night shift work could lead to <a href="http://news.health.com/2009/03/03/night-shift-work-hard-on-heart/">lower levels of leptin</a>, the hormone known to play a role in regulating weight, as well as affect blood sugar and insulin levels, Health.com. reported. The findings, published in 2009 in the journal <em>Proceedings of the National Academy of Sciences</em>, suggest that these changes could lead to a higher risk of <a href="http://news.health.com/2009/03/03/night-shift-work-hard-on-heart/">serious health conditions</a> like diabetes and heart disease, according to Health.com.




  • Makes You More Likely To Be Injured At Work


    Working the night shift could nearly double your risk of suffering a workplace injury, according to University of British Columbia researchers. Their findings, published in <a href="http://www.sjweh.fi/show_abstract.php?abstract_id=3124">the <em>Scandinavian Journal of Work, Environment and Health</em></a>, reveal that work injuries on a whole in Canada have gone down between 1996 and 2007, but they didn't go down at all among people who work at night. "The disruption of normal sleep patterns due to shift work can <a href="http://www.publicaffairs.ubc.ca/2010/11/02/mr-10-163/">cause drowsiness or fatigue</a>, which can lead to workplace injuries," study research Imelda Wong, a Ph.D. Candidate at the University of British Columbia's School of Environmental Health, said in a statement. "Our research shows that people working rotating and night shifts are more likely to experience an injury than those who work regular day hours."




  • Ups Depression Risk


    Numerous studies have suggested that shift work could have an impact on mental health. For example, a study in <a href="http://www.ncbi.nlm.nih.gov/pubmed/9891131">the <em>International Journal of Occupational and Environmental Health</em></a> showed that depression occurs at a higher rate among shift workers than non shift workers. And in a 2008 study in the <em>International Journal on Disability and Human Development</em>, researchers found that "shift work is suggested to increase the risk of <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2559945/">developing or aggravating mood disorders</a> at least in vulnerable individuals," though they also acknowledged that some experts say depression risk may have more to do with the actual job than working the night shift.




  • Sleep Help for the Graveyard Shift


    In this health video you will gain some help so you can sleep when you work odd hours through the night.