What is chronotype? Chronotype refers to the individual’s natural daily rhythm of when they wake up and go to sleep, and when their performance levels peak during the day.

We often associate unfavourable sleep habits, like staying up late and having trouble waking up, with teenagers. This is because adolescents and young adults naturally shift towards an evening chronotype. Chronotype refers to an individual’s inclination for being a ”morning person” or an ”evening person.”  Some people feel more alert and energetic early in the day, while others hit their stride later in the afternoon or evening.

Evening chronotypes are often out of sync with societal schedules, as school and work typically start early in the morning. Studies have shown that having an evening chronotype increases the risk of various health issues, including having a less healthy diet. It’s also no surprise that individuals with a later chronotype tend to experience more irregular sleep schedules, shorter sleep duration, and ”social jetlag”—a term for when the body’s internal clock is out of sync with daily societal demands, like school or daycare schedules.

Chronotype begins developing at a very young age, and while it may shift slightly over the lifespan, it is largely considered a trait driven by one’s genes. Even young children can exhibit a later chronotype, which can be concerning since preschool often follows early start times in line with societal norms. While much of the existing research on chronotypes has focused on adults and teenagers, there is limited exploration of how chronotype in young children influences their sleep habits and diet.

The 50^th peer-reviewed scientific publication from the Increased Health and Wellbeing in Early Education and School Children (DAGIS) study in Finland explored the associations between sleep habits and chronotype with the diet of young children. Researchers collected sleep and chronotype data through accelerometers that children wore for one week. Additionally, information of diet was gathered from a three-day food diary, allowing the researchers to assess total energy and nutrient level intake as well as consumption of fruits, vegetables, sugary foods, and sugar-sweetened beverages.

The study revealed several important findings regarding the associations between sleep habits and chronotype with diet among preschoolers. First, children with an evening chronotype tendency showed poorer sleep habits compared to those with an intermediate chronotype tendency. These children had greater day-to-day variability in both sleep timing and duration, as well as greater social jetlag. Second, having a later chronotype was associated with less healthy diet quality. Children with a later chronotype were more likely to consume foods high in added sugar, while also consuming fewer vegetables and less fiber. This is concerning because childhood nutrition is crucial for long-term health, including the risk of developing overweight or obesity. Third, contrary to what might have been expected, shorter sleep was not associated with poorer diet or higher energy intake. Overall, these findings suggest that, even with sufficient sleep duration, it may be beneficial to consider the child’s chronotype when trying to promote healthier eating and sleeping habits.

This research lays the groundwork for future studies to investigate the impact of evening chronotype tendencies in early childhood. There is still much to uncover regarding the relationship between sleep and diet, and how one affects the other. Ongoing research from DAGIS will continue to explore how early life chronotype may also associate with weight outcomes over time. Stay tuned!

Read the full article here.

Text: Anna Abdollahi