What causes fatigue?

Fatigue, or what we refer to as drowsiness, is the state right before sleep onset. Most people will experience fatigue after completing a heavy gym session, but they will not necessarily be in danger of experiencing a micro-sleep. (A micro-sleep is a temporary episode of sleep lasting up to 30 seconds, often called a ‘nap’ in the US). Yet micro-sleeps can occur when you are doing critical but repetitive tasks, without being aware of impending danger. Most people refer to this as fatigue and so we’ll use that term in this article.

At one point or another, we’ve all experienced fatigue. Whether it’s a particularly hectic week (with work, the kids and your social life) or a hot summer’s night resulted in a restless and poor sleep, you might feel like it’s impossible to avoid fatigue.

There are a number of habits and reasons why fatigue can be more prevalent in some people over others, and we’ve outlined a few below. Read the list and think about how these factors might be affecting you.

Fatigue symptoms

The following fatigue symptoms and causes are, unfortunately, quite common. Any one (or a combination of a few) can leave you feeling sluggish and lethargic, impacting your work, health, and social life.

Poor health or diet

Put down the donut and slowly back away.

Sweet and starchy carbs send your blood sugar levels on a joyride, erratically jumping from energy highs to lows, and even that temporary sugar rush will leave you feeling even more sluggish than before.

Avoid heavy, sugary foods and drinks, in particular ones with high GI indexes like white rice. And stop skipping breakfast! A good quality breakfast provides you with sustained energy to begin your day.

Some foods which might help fight fatigue: oatmeal, nuts, eggs, whole grains, spinach and of course, more fruits and vegetables.

Sleep disorders

Think of the term ‘sleep disorders’ and the first that come to mind likely include insomnia, sleep apnea, restless leg syndrome, night terrors and narcolepsy.

The common outcomes of these sleep disorders (and others) is that sleep is of poor quality and/or regularly disrupted. Making your way through a workday that follows a poor night’s sleep leaves us feeling completely drained.


When your adrenal glands (also known as “the glands of stress”) are fatigued, then so is the rest of you.

Guilt, depression and overwork are some common factors that exhaust and overstimulate your adrenal glands so that over time they struggle to perform their normal functions, which include:

> Regulating stress

> Controlling your body’s “fight or flight” response

> Releasing the hormone cortisol (which plays a vital role in our sleep/wake cycle)

Sleep debt

You can’t stop yawning, your eyelids feel heavy, and you’re dreaming of bed.

It’s just ticked over to 2pm on Wednesday afternoon – how is there still three hours of work to go?

Maybe you shouldn’t have stayed out so late last night, especially after those two late nights on the weekend.

Sleep debt, just like real debt, is combatted by only one method: to repay it. Each hour you build up goes into your sleep bank, and the only way to clear your account is to make up for the hours lost with good quality sleep.

Until you can repay that debt, your chances of being involved in a drowsy- or fatigue-related incident increase, and you feel fatigued, irritable and weary.

Your job

In particular, shift work.

If you’re awake outside of regular sleep/wake hours (and as a result disrupting your body’s natural circadian rhythm) then it’s likely you feel fatigued, sluggish and lethargic.

A lack of recovery time or using this time off work poorly can have detrimental effects on your health with fatigue being just one of them. Shift workers have an increased risk of experiencing:

  • A decline in the body’s immune system
  • Depression
  • Insomnia
  • Strain on personal relationships
  • More cognitive errors
  • An accident or injury (regardless of whether this occurs at work or when an employee is travelling to work or on their way home)

Fatigue does not necessarily mean drowsiness

As mentioned above, there remains an overlap when it comes to fatigue and drowsiness, and while these terms are often interchanged, they do differ significantly. Drowsiness is the dangerous state right before sleep.

The conditions and circumstances we’ve listed above are all valid causes for fatigue, but drowsiness is the state than we cannot control. It’s that moment right before we fall asleep in bed or nod off on the couch – and it is a period we are not able to remember.

Fatigue, but more specifically drowsiness, can only be cured with sleep. Temporary fixes like coffee are not sustainable solutions, and, combined with a vehicle or when making critical life-impacting decisions, drowsiness can prove deadly.

If you’re concerned about fatigued or drowsy employees putting their health and lives at risk, then you might need Optalert’s technology.

Get more information on Optalert’s all-hour protection that keeps your employees safe to work, at work and home from work.