Larks and Owls

Larks and Owls

An individuals tolerance towards shiftwork has been found to be related to his Chronotype, which is the scientific name given to his particular circadian rhythm pattern.

Humans can be categorized as falling into three chronotypes, using measures such as the Horne-Ostberg Morningness-Eveningness Scale. The three types are "morning" (Larks), "evening" (Owls) and "indifferent".

"Morning" and "evening" types each represent approximately 15% to 20% of the human population whilst the remaining 60% to 70% of the population fall into the indifferent category.

Morning-type individuals (Larks) can be described as those persons who naturally waken about 2 hours earlier than the majority of the population and are ready for sleep between 8pm and 10pm. To them, midnight is the middle of the night. Larks cope more easily with Early shifts.

Evening-type individuals (Owls) can be described as those persons who naturally waken about 2 hours later than the majority of the population and don't feel sleepy until between 12 midnight and 2am. Owls cope more easily with Late shifts.

If you don't readily identify yourself as a "Lark" or an "Owl" then you most likely fall into the "indifferent" category. If you have any doubts, then you can take the Morningness-Eveningness Test which is attached to this page.

Studies show that in the short term Larks have greater difficulty coping with nightshift than Owls, as their natural tendency to wake early reduces their day time sleep after a nightshift.

If you identify yourself as a Lark then 'napping' in the evening is one strategy to help boost mental alertness on nightshift, although it doesn't replace quality sleep time.