Tired all the time is the title of a feature piece by Emma Young in the 15 October 2015 New Scientist. The subtitle of the piece is “Why fatigue isn’t just about sleep.” Perhaps the most obvious answer is that life is more exhausting than it has ever been. There are the many competing demands of work and family together with the ever-present smartphone notifications. Today’s omnipresent technology is a likely reason that we feel as if we’re running on empty. There is a book titled “Exhaustion: A history” written by Anna Katharina Schaffner, who is a historian at the University of Kent in Canterbury, UK. She has documented that “people through the ages have consistently complained of being worn out, and harked back to the relative calm of simpler times.” Throughout the centuries fatigue has been blamed on the alignment of the planets, a lack of godliness, and even an unconscious desire to die. Schaffer says that “Freud argued that a very strong part of ourselves longs for a state of permanent physical and mental rest.”
In the 19th century the American physician George M. Beard claimed that neurasthenia was caused by exhaustion of the nervous system and was responsible for physical and mental fatigue as well as irritability, hopelessness, bad teeth, cold feet, and dry hair. Beard blamed neurasthenia on the advent of steam power and newfangled inventions such as the telegraph. Schaffer says that “Beard feared that the modern subject was unable to cope with such chronic sensory overload.”
A lack of sleep is another apparent cause of fatigue. Researchers are able to distinguish between the need for sleep and fatigue, considering them to be closely related but subtly different. The sleep latency allows the subtle distinction between sleep and fatigue. It is widely used in sleep clinics and is based on the idea that if you lie down somewhere quiet during the day and fall asleep within a few minutes, you are either lacking sleep or potentially suffering from a sleep disorder. If you don’t drop off within 15 minutes or so, yet still feel tired, fatigue might be the problem.
Mary Harrington is one of the researchers looking for a tell tale biological signal. One possibility is that daytime fatigue stems from a problem with the circadian clock, which regulates periods of mental alertness through the day and night. This regulation is done by the brain’s suprachiasmastic nucleus (SCN), which coordinates hormones and brain activity to ensure that we feel generally alert during the day. Normally, the SCN orchestrates a peak in alertness at the start of the day, a dip in the early afternoon, and a shift to sleepiness in the evening. The amount of sleep you get at night has little impact on this cycle. How alert you feel depends on the quality of the hormonal and electrical output signals from the SCN. The SCN uses the amount of light hitting the retina to set its clock, so that it keeps in line with the solar day. Too little light in the mornings, or too much at night, can disrupt SCN signals, and either can lead to a lethargic day. Harrington says “I think circadian rhythm disruption is quite common in our society and is getting worse with increased use of light at night.” She says the if you spend the day feeling as if you have never quite woken up properly, but are not sleepy at bedtime, a poorly calibrated SCN might be to blame. She recommends spending at least 20 minutes outside every morning and turning off screens by 10 pm to avoid tricking the SCN into staying in daytime mode. Another way to reset the SCN is through exercise. Studies have linked exercise to reduced fatigue. Harrington says that exercise can make a big difference. People who start exercising regularly often report sleeping better when some studies show that they don’t actually sleep any longer. Quality of sleep appears to be more important than quantity.
Reducing fat levels can also be helpful. Body fat not only takes more energy to carry around, but also releases leptin, a hormone that signals to the brain that the body has adequate energy stores. People who carry excess fat also show higher levels of inflammation. Body fat stores large levels of cytokine, which are released into the bloodstream. In addition to stimulating the immune system, cytokines also make you feel drained of energy.
Even if you are not overweight, inflammation could still be running you down. A sedentary lifestyle, regular stress, and poor diet have all been lined to chronic lower-level inflammation. There is also preliminary evidence that disruption of circadian rhythms can increase inflammation.
Low dopamine is also implicated in depression as it reduces availability of serotonin. Since the vast majority of people with major depression report severe fatigue, it’s not surprising that depression is also a potential common in fatigue.
Harrington’s advice is not to let fatigue stop you doing something you enjoy. Force yourself to keep at it because a potent reward could trigger the release of dopamine in brain areas linked to motivation and alertness. Or do something stressful: the release of adrenaline could help you overcome lethargy. Ideally put stress and enjoyment together.