Although it is a common phenomenon, it can have a profound impact on the productivity and safety of individuals.
Specifically, sleep inertia can impact the safety of workers in hazardous occupations or impair decision-making by emergency service personnel, including healthcare workers and firefighters, which can influence the safety of others.
Likewise, reduced alertness over the course of the day due to inadequate sleep is associated with lower productivity and an increased risk of traffic accidents.
However, there is limited scientific evidence on the factors that influence the levels of alertness after waking up.
In the present study, the researchers assessed the factors associated with daily variation in morning alertness in the same individual.The researchers first examined the impact of four prespecifiedfactors on the day-to-day variation in alertness observed within the same individual.
They assessed the impact of the previous night’s sleep profile, physical activity on the previous day, the nutritional composition of breakfast, and post-breakfast blood sugar levels on morning alertness. Participants recorded their dietary intake and alertness on the ZOE study app, through the study. The study was funded by ZOE Ltd.
To examine the impact of these factors, the researchers used data collected over a 2-week period from 833 individuals aged 18–65 years. The participants had to wear a wristwatch accelerometer throughout the entire study period to facilitate the collection of data on their sleep profile and physical activity levels.
The researchers then examined the impact of the macronutrient composition of breakfast on morning alertness. They provided calorie-matched standardized breakfasts of varying nutritional compositions, including high carbohydrate, high protein, and high fiber meals to each participant, which were consumed on different days.
The researchers compared the participants’ alertness levels after the consumption of each of these meals with that after a reference meal that provided moderate levels of carbohydrates and proteins.
Among the different standardized meals provided to the participants, consumption of a high carbohydrate breakfast was associated with higher levels of morning alertness than the reference meal.
In contrast, the high protein breakfast was linked to lower alertness levels than the reference meal.
The researchers also examined how the changes in blood glucose (sugar) levels after the consumption of breakfast influenced morning alertness levels.
Based on each participant’s baseline sleeping profile, the researchers found an association between sleep duration and sleep timing with morning alertness levels.
Specifically, when a participant slept longer than usual or woke up later than their usual time, they were more likely to show higher levels of alertness the next morning.
Higher levels of physical activity during the previous day were also associated with increased morning alertness.
Only physical activity levels during the 10 most active hours of the previous day were positively correlated with morning alertness levels.
Conversely, physical activity during the nighttime was associated with lower morning alertness.
For the evaluation of morning alertness levels, the participants recorded the levels of their alertness on an app on a scale of 0–100. They reported their first alertness rating at the start of breakfast and then intermittently over the subsequent 3 hours.
The researchers also examined how the changes in blood glucose (sugar) levels after the consumption of breakfast influenced morning alertness levels.
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