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JOURNAL

Introducing Chronotypes Part 3

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Work schedules and city life. In the third of our three part series on chronotypes, Sandrine Ceurstemont explores what happens when your chronotype is out of sync with society.

Typical school times and a 9-to-5 workday aren’t ideal for many chronotypes. But in many countries, society is now adapting to cater to individual sleep preferences.

Extreme chronotypes may feel out of sync with schedules imposed by modern life. Early start times dictated by work and school are particularly challenging for night owls who would naturally sleep in later. But urban lifestyles typically cater to slightly later chronotypes than life in rural areas1 as there is more evening activity and nightlife. A move from the city to the countryside is also likely to modify a person’s chronotype due to more exposure to natural light during the day and less artificial light after dark.

When social schedules conflict with preferred sleeping times of a chronotype, it results in social jet lag,2 a term invented by Till Roenneberg, a professor of chronobiology at Ludwig Maximilian University of Munich in Germany. 

Feeling groggy is one of the consequences but it can lead to more serious health problems too. Night owls seem to be at greater risk of developing major depression, which is thought to be linked to the social jet lag they experience, although more research is needed to back it up3. A link between night owls and an increased risk of heart failure4 and cardiovascular disease5 was also found in preliminary results. And there is some evidence6 showing that mismatched sleeping patterns are a risk factor for anxiety, diabetes, and memory consolidation. 

Misaligned chronotypes have gained particular attention when it comes to school start times. A growing body of research shows that adolescents are naturally inclined to start the day later due to age-related chronotype shifts. Having to wake up early to go to school can therefore result in chronic lack of sleep and social jet lag, which has been linked to behavioural problems and poor academic achievement7. Teenagers who are night owls have also been found to be more affected by a lack of sleep8, functioning and achieving less well than larks.

In several countries, school start times are being revised. In Israel, for example, schools used to start before 8 am but most don’t anymore.9 And a few months ago, California became the first state in the US to pass a law mandating later start times for middle schools and high schools10.

having to wake up early to go to school can result in chronic lack of sleep which has been linked to behavioural problems and poor academic achievement

Applying the same principle to universities could help too. A study aiming to optimise the cognitive functioning of11 undergraduates found that much later start times, after 11 am, were ideal. They also found that any proposed start time would put at least one chronotype at a disadvantage so having multiple sessions at different times would be a solution.

Enabling flexible hours for workers could help cater to different chronotypes too. One study12 has shown that morning types earn significantly more than those who prefer late nights since their natural rhythms are better aligned with societal norms. They were more productive and able to devote more time to a range of activities including extra paid work.

Being allowed to work when one feels at one’s best would especially benefit owls, where one study showed a gain in optimal work hours of 30%13. In another experiment, shift schedules in a factory were adjusted to suit different chronotypes14, where late types wouldn’t be given early shifts for example.  Employees that had extreme chronotypes reported that their sleep improved, both in quality and duration, and there was a positive impact on their general wellbeing on workdays. 

one study15 showed a 30% gain in performance by being 
allowed to work when you feel at your best

More research is needed to see if tailoring work hours to different chronotypes also has a long-term impact on health. But there is now a greater awareness of the link between sleep and performance and how chronotypes are involved16. With more people now working from home or choosing flexible hours, we may get closer to the goal of waking up without an alarm clock. 

If you missed the other two parts to this series, Part 1 explores what chronotypes are and what determines them, and Part 2 investigates how chronotypes control your body, hormones and physical and mental performance.

Sandrine Ceurstemont is a freelance science and technology writer based in London, UK, and Morocco. Previously on staff at New Scientist for nine years, she now writes for a variety of outlets such as BBC Future, National Geographic, the European Union’s Horizon magazine, and Scientific American. She is more night owl than lark.

Footnotes
1  – tbc
2 The body-clock science behind later school start times – BBC Worklife
3 Social Jetlag, Depressive Symptoms, and Longitudinal Outcomes in College Students  – VCU Scholars Campus
4Associations of common noncommunicable medical conditions and chronic diseases with chronotype in a population-based health examination study – Chronobiology International
5 Associations between chronotype, morbidity and mortality in the UK Biobank cohort  – Chronobiology International
6 Identifying the Best Times for Cognitive Functioning Using New Methods: Matching University Times to Undergraduate Chronotypes – Frontiers in Human Neuroscience
7 Adolescent sleep misalignment: a chronic jet lag and a matter of public health – Journal of Physiology-Paris
8 Sleep-deprived brains may be asleep and awake at the same time – Horizon The EU Research and Innovation Magazine
9  Sleep-deprived brains may be asleep and awake at the same time – Horizon The EU Research and Innovation Magazine
10 California becomes first state in the country to push back school start times – Los Angeles Times
11 Identifying the Best Times for Cognitive Functioning Using New Methods: Matching University Times to Undergraduate Chronotypes – Frontiers in Human Neuroscience
12  Do Morning-Type People Earn More than Evening-Type People? How Chronotypes Influence Income – Annals of Economics and Statistics
13 When Should We Start Work? Circadian Sociology Analysis of the Conflict Between Biological and Social Time – SocArXiv Papers
14 Aligning Work and Circadian Time in Shift Workers Improves Sleep and Reduces Circadian Disruption – Current Biology
15 When Should We Start Work? Circadian Sociology Analysis of the Conflict Between Biological and Social Time – SocArXiv Papers
16 Why sleeping in could make you a better worker – BBC Worklife

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