t shouldn’t be a mystery that people operate at different levels of alertness at varying times of the day.  According to Circadian 24/7 Workforce Solutions, a shiftwork consulting firm based in Stoneham, MA, people should think of these factors as “switches” that can be turned on or off at any time.  Recognizing them can help you stay alert on the job.

Sense of danger, interest or opportunity
Nothing can move people from a drowsy state more effectively than the imminent threat of danger, or surviving a near miss.  A stimulating task or opportunity triggers a similar response.  On the flip side, monotonous tasks cause alertness to fade.  An endless stretch of boring road or a quiet night in a plant where everything is running smoothly can bring on drowsiness.

Muscular activity
Physical activities such as walking or stretching help keep people alert.  On the other hand, extended periods without much movement, such as sitting in a chair or car, makes people less alert.

Environmental light
Bright light tends to increase alertness, particularly during overnight hours.  Whether you’re at home or on the job, dim light or darkness makes people sleepy.

Time of day on the circadian (body) clock.
Circadian  rhythms, which are daily ups and downs in blood pressure, body temperature, hormone levels and other physiological traits, have a major effect on our alertness.  People generally experience peak levels of alertness during the morning and early evening.  It’s much harder to stay alert in the early afternoon and during overnight hours.

Sleep bank balance
How long you’ve been awake and how much sleep you’ve received in recent days affects your alertness level.  If you only sleep four or five hours a day for several days in a row, you’ll build up a sleep debt that leads to decreased alertness.  A long spell of sleep acts as a “deposit” that helps offset your sleep debt.

Sound
Both sleep and alertness can be affected by different sounds and volumes. Listening to AC/DC energizes people more than listening to Kenny G.  However, if you are driving while exhausted, you’re mistaken if you think that loud, fast music is going to prevent you from nodding off.

Ingested nutrients and chemicals
Caffeine and other stimulants temporarily increase alertness.  Others, such as sleeping pills, antihistamines, melatonin and certain foods may induce sleep.  Of course, some of these substances have serious drawbacks because of their negative effect on overall health and potential for abuse or addiction.

Temperature and humidity.
Cool, dry air, especially on your face, makes it easier to stay alert, while heat and humidity make you drowsy.  Similarly, a cold shower is invigorating, while a warm bath prepares you for sleep.

Taken from Safety Talks Issue Jan. 2010