Your chronotype describes your natural preferences for when you like to rise in the morning, and the time by which you’d prefer to go to bed at night. You will be aware of your most energetic and productive time of day, and conversely, when you start to lag. Put simply, we’re describing a spectrum running from morning types (larks) to evening types (night owls), with some of the population lying in between.
Due to work and other commitments, our schedules often cannot accord with our natural inclinations. It’s worth thinking about our chronotype because then we can be aware of any associations it may have with a greater tendency towards certain behaviours, imbalances or even disease.
The Different Chronotypes
Chronotype can shift during life: children are often larks, become night owls in their teens, then can shift back in adulthood. Older people may often be larks once again. It can also be influenced by genetics, cultural norms and light exposure.
Around 15% of the population are early risers, and particularly productive from dawn until noon. Another 30% are night owls, and productive at night; creative and artistic types can fall into this category. Most people, that is 40%, are most productive between 11am and 6pm, and their activity aligns with the sun. The final 15% of the population has difficulty establishing a sleep routine. Their productivity window may be from 10am to 2pm.
Insufficient sleep can affect anyone’s health, but if you are a night owl who needs to be up early for work, college or to get the kids ready, then follow all the usual sleep hygiene measures and try to establish a regular bedtime.
Chronotypes and Health
Although chronotype is just one of many health determinants, it’s useful to be aware of some of the associations that research has uncovered. That way, you can try to make sure that other, controllable factors aren’t going to conspire to further increase your risk of developing certain problems. Being a night owl may slightly increase the risk of anxiety, depression, eating disorders, obesity, type 2 diabetes and sleep apnoea for example.
Elderly individuals with an evening chronotype are more likely to be current smokers, have more sleep disturbance, engage in more sleep-interfering behaviours (evening caffeine or alcohol consumption, heavy meals before bedtime), and to have lower physical activity.
A Finnish study found evening types had a 2.5 fold increased risk of developing type 2 diabetes compared with morning types. Evening chronotype may be more associated with diabetes in men and metabolic syndrome in women.
Chronotypes and Eating Habits
Curious dietary patterns have emerged in various studies. Remember these are associations, some of which are not altogether surprising, but causality has not been established. In adolescents, evening types consume more coffee, energy drinks, alcohol and fast food. Young adult evening types can have inadequate intakes of several minerals and vitamins.
Morning chronotypes exhibit greater regularity in their eating behaviour. Adolescent evening types exhibit greater differences between weekday and weekend breakfast times. This is concerning given that patterns at this age can be laid down for life and that irregularity of meal patterns has been identified as a risk factor for cardiometabolic disorders.
Turning to adults, in a UK survey morning types consume 25% more servings of fruit and 13% more servings of vegetables per day compared with evening types. In a Finnish survey, those with a leaning towards the morning chronotype consumed more wholegrains, rye, potatoes and vegetables, while those leaning towards the evening type consumed more alcohol, sugar and chocolate. Evening types were more likely to be smokers, physically inactive, and have lower perceived health quality.
Adults with an evening chronotype skip breakfast more often than do individuals with a morning chronotype, and breakfast skipping has been related to lower physical activity in some studies.
Summary
A good deal of further research will be needed to establish causality in the above health observations. On the face of it, data suggests being a night owl is not particularly good for us. For now, if it just makes you consider how a later bedtime might in subtle ways lead to less healthy habits and eventually poorer health, then this will have been a useful read.
From the traditional Chinese medicine perspective, you may recognise that aligning our rhythms broadly with sunrise and sunset, and cultivating regularity of mealtimes, are principles that have been taught for centuries.
Further reading: (1) Chronotype: Implications for Epidemiologic Studies on Chrono-Nutrition and Cardiometabolic Health. Advances in Nutrition, January 2019. (2) Editorial: Chrononutrition and health. Frontiers in Nutrition, 14 November 2024.
