- Individuals tend to experience different levels of alertness from day to day, while also differentiating themselves from other individuals by their average daily alertness levels.
- A recent longitudinal study suggests that the previous night’s sleep pattern, physical activity during the previous day, and nutritional composition of breakfast were related to daily variation in a person’s morning alertness levels.
- The study also found that non-genetic factors, including mood, sleep quality, age and frequency of daily food intake, predicted differences in morning alertness between individuals.
- The study reported a modest effect of genetic factors on daily alertness, suggesting that interventions aimed at modifying non-genetic factors could help improve daily alertness levels.
Impaired alertness immediately upon waking and throughout the day can negatively impact cognitive and motor performance and increase safety risks.
A recent study published in
These results suggest that interventions undertaken at the individual and societal level targeting these non-genetic factors could help mitigate the negative consequences associated with impaired alertness.
Although this 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 performing hazardous activities or impair decision-making by emergency service personnel, including healthcare workers and firefighters, which can influence the safety of others.
Similarly, reduced alertness during the day due to insufficient sleep is associated with lower productivity and increased risk of traffic accidents.
However, there is limited scientific evidence on factors that influence alertness levels after waking.
In the present study, researchers assessed factors associated with daily variation in morning alertness in the same individual.
They also looked at the role of genetic versus non-genetic factors in influencing differences in average levels of morning alertness among individuals.
The researchers first examined the impact of fourfactors on the daily variation in alertness observed in the same individual.
They assessed the impact of the previous night’s sleep pattern, previous night’s physical activity, nutritional composition of breakfast, and post-breakfast blood sugar on morning alertness. Participants recorded their food intake and alertness on the ZOE study app, throughout 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 people between the ages of 18 and 65. Participants were required to wear a wristwatch accelerometer throughout the study to help collect data on their sleep profile and physical activity level.
For assessment of morning alertness levels, participants recorded levels of their alertness on an app on a scale of 0 to 100. They reported their first alertness rating at the start of breakfast and then intermittently during of the next 3 hours.
Based on each participant’s baseline sleep profile, the researchers found an association between sleep duration and sleep timing with levels of morning alertness.
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 at night was associated with reduced morning alertness.
The researchers then looked at the impact of the macronutrient composition of breakfast on morning alertness. They provided each participant with standardized calorie-matched breakfasts of different nutrient compositions, including meals high in carbohydrates, protein and fiber, which were eaten on different days.
The researchers compared the level of alertness of the participants after consuming each of these meals with that after a reference meal providing moderate levels of carbohydrates and protein.
Among the different standardized meals provided to participants, consumption of a carbohydrate-rich breakfast was associated with higher levels of morning alertness than the reference meal.
In contrast, the high-protein breakfast was linked to lower levels of alertness than the reference meal.
The researchers also looked at how changes in blood glucose (sugar) levels after eating breakfast influenced levels of morning alertness.
Regardless of breakfast composition, a lower glycemic load, a measure of the impact of food intake on blood sugar, after breakfast, was associated with greater morning alertness.
Notably, these four factors influenced morning alertness levels independently of each other.
Jeff Kahn, CEO and co-founder of energy and sleep tracking subscription app Rise Science, who was not involved in this study, commented on the results, saying Medical News Today this:
“The study helps show that positive health and wellness outcomes, in this case, greater alertness, can be achieved through a variety of levers. The four independent impact inputs they cite – longer than normal sleep duration, prior daytime exercise, breakfast composition high in carbohydrates but still diverse in macronutrients, and lower glycemic response in the hours following breakfast consumption are unobtrusive tools in our performance toolbox that we can use and benefit from, even if we are not able to achieve all four at all times.”
If these factors explained the daily differences in morning alertness in the same individual, the authors also looked at factors that could explain why some participants had higher average levels of alertness than others.
In other words, researchers have been interested in genetic and/or lifestyle factors that may influence an individual’s characteristics or average levels of daytime alertness.
The researchers found that positive mood, older age, reduced daytime meal frequency and better quality of sleep were predictors of an individual’s average daily alertness levels.
The present study included both twins and genetically unrelated adults. This allowed the researchers to examine the extent to which genetic factors could influence daily alertness levels in the twins.
The researchers found that genetic factors had a small impact on an individual’s alertness levels, suggesting a greater impact from lifestyle factors that could be changed.
Dr. Andrew McHill, a sleep researcher at Oregon Health & Science University, not involved in this study, said that “[u]What is unique to this current study are the wide-ranging predictors that were collected – sleep, food and activity – and the ability to distinguish these behaviors from genetic influences using the twin study.
“Using this type of analysis allows for a more accurate assessment of potentially modifiable behaviors to improve alertness the next day. This is not only exciting for potential individual and social targets to improve safety and health, but also for the research community, as it provides further testable hypotheses for future examinations to identify the exact mechanisms behind these observed changes in alertness,” he added.
The researchers acknowledged that their study had some limitations. For example, morning alertness levels in the study were based on self-reports and may be subject to bias.
The study also did not take into account differences in light exposure in the morning, a factor known to significantly improve alertness.
The researchers further noted that all of the standardized breakfasts consisted of carbohydrates, proteins, and fats and varied only in the levels of these macronutrients.
They cautioned that these findings should not be taken at face value and lead to the adoption of carbohydrate-only meals for breakfast.
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