In some jobs, employees regularly work outside of the normal office hours of 9am to 6pm, as their co-workers or clients operate in a different time zone on the other side of the world.
Such work hours, in the long run, can disrupt employees' biological clock.
The good news, however, is that by taking small practical steps, one can enjoy his work and keep his health intact, too.
"If you cannot avoid shift work, there are ways to reduce its health risks," said Dr Fong Yuke Tien, senior consultant and director of occupational medicine at the Singapore General Hospital's Department of Internal Medicine.
The human body's circadian rhythm can be thought of as an internal 24-hour biological clock that regulates and synchronises the body's physiological processes, according to the natural patterns of daylight and darkness.
This internal clock instructs the brain to release more melatonin - a sleep-inducing hormone - when it detects less sunlight in the external environment.
This is why most people feel sleepy at night.
"Shift workers work odd hours and under artificial indoor lighting," said Dr Fong.
"During a night shift, the body will adapt to a changed sleepwake pattern. When this pattern of wakefulness at night is persistent over weeks, hormonal adjustments will occur to allow us to adapt to staying awake at night and sleeping in the day," he said.
Those who work odd hours and experience headaches, insomnia, excessive sleepiness and poor concentration could be suffering from shift-work sleep disorder.
It is caused by continual sleep deprivation and interruption.
Employees can be more prone to accidents
When work is continuous over long hours with no rest break, fatigue sets in and a sleep debt will accumulate.
Employees with these problems will be less attentive and more prone to accidents.
As a result, performing fine work or work requiring a high-attention span, as well as operation of heavy machinery, can become problematic.
Beyond sleep disorders, long-term shift work disrupts the body's hormonal, digestive, metabolic and cardiovascular systems.
It also increases one's health risks for Type 2 diabetes, cardiovascular disorders, obesity, cancer and gastrointestinal problems.
"Some people prefer shift work because of its variety, flexibility and higher pay," said Dr Fong.
"By making sure you have enough sleep, rest every two to three hours and exercise, you can lessen the risk of excessive fatigue that can lead to health problems."
Here are seven tips to help you cope better when working odd hours.
1. TRY TO TAKE ON FEWER CONTINUAL NIGHT SHIFTS
Working during night shifts continually for weeks in a row will change your sleep pattern and make it harder for you to fall asleep during your normal sleeping time.
2. STICK TO A SHIFT-WORK PATTERN
A set shift-work pattern means working the same number of hours and at the same time every day. This may help the body adjust better to the work schedule.
3. GET ENOUGH REST
Working continuously without a rest break to sleep will lead to fatigue.
This will make the worker more prone to accidents, increase inattention and increase sleep debt.
4. HAVE A SLEEP-CONDUCIVE ROOM
Keep your bedroom quiet and dark, as such an environment is more conducive for sleep.
More tips ahead
5. KEEP A FIXED SLEEP SCHEDULE
Try to sleep at about the same time every day if you are on anight shift, to help your body adjust to a new sleep schedule.
6. AVOID CAFFEINE AND ALCOHOL
Caffeine and alcohol are stimulants that will keep you alert and prevent sleep.
Shift workers who drink more than two cups of coffee and one glass of alcohol every day have poorer-quality sleep than those who do not.
So, try and avoid caffeine and alcohol several hours before your scheduled bedtime.
7. EAT HEALTHILY
Choose healthy snacks such as fruit and a diet high in vegetable content to curb your hunger during shift work.
Avoid high-fat snacks, as well as fried and spicy food that are more difficult to digest at night - they may cause gastrointestinal discomfort.
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