If you are feeling exhausted all the time, you must need more sleep, right? Not necessarily. Although the CDC estimates that around 35 percent of us are coming up short in the sleep department, research is suggesting that fatigue can plague a person regardless of the amount of sleep they get. Fatigue is a costly condition, too, costing American employers about $100 billion annually as more than 20 percent of us struggle with fatigue that is serious enough to disrupt our daily lives.
According to the National Highway Traffic Safety Association (NHTSA), fatigue contributes to about 7 percent of all road accidents. The NHTSA also says that fatigue is responsible for 2.6 percent of all traffic fatalities, causing almost 886 fatal crashes, 37,000 injury crashes, and $45,000 property-damage only crashes every year. This is a conservative estimate, and NHTSA confirms that the 2009 Massachusetts Special Commission on Drowsy Driving might be right; if it is, fatigue is responsible for as many as 1.2 million crashes, 500,000 injuries, and 8,000 fatalities each year.
If all we needed to do to prevent fatigue and its devastating effects was to get everyone to spend a few extra hours in bed each night, we might be able to find a simple solution. But research is showing that fatigue is caused by sources beyond sleep deprivation. If fatigue is more than feeling tired, how do we know what it really is? Smith College neuroscientist Mary Harrington, one of several researchers looking for a reliable biological signal for fatigue, says there are a few possibilities.
Fatigue might be tied to a problem with the circadian clock, which is regulated by the suprachiasmatic nucleus in the brain. Normally, this area coordinates brain activity and hormones for a peak in alertness early in the day. Amount of sleep isn’t important, but light hitting the retina is, so too much light at night can be disruptive (as anyone who has experienced jet lag knows).
High body fat and levels of leptin released by fat cells may also be the issue. Leptin is a hormone that tells the brain when the body has enough energy. Higher leptin levels have been linked to increased fatigue and, presumably, less motivation to go out hunting and gathering. Furthermore, people whose bodies store excess fat also tend to exhibit more inflammation. This causes cytokines, which make you feel fatigued and drained, to be released into the body.
Another possible source of fatigue that researchers are looking at is depression. However, as with the other two possibilities, it seems that depression alone can’t solve the fatigue riddle — at least not when fatigue exists in so many millions of people.
If we are going to solve the mystery of fatigue and the many costs associated with it, we need to invest more into studying it. While the National Institutes of Health is searching for the elusive roots of fatigue, Harrington told New Scientist that attention from more researchers and improved animal models will be needed to put fatigue to bed once and for all.
“I’ve done a lot of work on this because I think we can crack it,” Harrington said. “But I do feel pretty alone out there.”