Children whose morning routines started later during COVID-19-related school closures are at a higher risk of falling into unhealthy lifestyle habits during future emergency situations, according to research from Tokyo.

Researchers at the University of Tokyo’s Institute for Future Initiatives and Graduate School of Medicine believe that keeping normal eating and sleeping schedules throughout school closures is key to maintaining a healthy lifestyle.

The team conducted a cross-sectional survey of 11,958 elementary and junior high school students from 48 schools and educational organizations across 14 prefectures in June 2020. The findings were based on the responses of 6,220 children between the ages of 8 and 15, whose responses provided the most conclusive information on their dietary habits.

The researchers divided the children into four groups based on their wake-up and breakfast times during school closures.

Of these groups, 26% woke up the latest — between 8:00 a.m. and 10:00 a.m. — and ate breakfast around 9 a.m. or later. Additionally, 42% of the children who woke up the latest also skipped breakfast at least once a week.

Moreover, students who woke up much later than the other groups consumed less fruit, vegetables, dairy products and other nutrient-rich foods, putting them at higher risk of falling into unhealthy lifestyles. Instead, they tended to consume more candy, soft drinks and other sugary foods and beverages.

Additionally, 61% of the latest-riser group had much more screen time while schools were closed: over four hours a day in front of TVs and smartphones, which was double the time of the group with the earliest risers.

In addition, the students who woke up and had breakfast the earliest when schools closed the first time were found to maintain the same habits when pandemic-related school closures happened again.

“The results suggest that it is important for children to maintain the habit of sleeping and eating at the same time as in normal times — even if schools are closed again in the future for an extended period of time due to infectious diseases or natural disasters,” the team said.

The results were published online by Cambridge University Press in May.