Sleep in everyday life – relationship to mood and performance in young and older adults
In today’s society, many individuals suffer from disturbed and short sleep. Laboratory studies show that sleep deprivation for one night has profound adverse consequences for mood and performance, which appear to be larger in young than older adults. However, much less is known on the impact of day to day variations in sleep that individuals normally encounter in their daily life. Using mobile experience sampling, we will combine accurate real-time repeated measures with a naturalistic setting to address the following research gaps: (i) how variable/stable is everyday sleep in young compared with older adults? (ii) how do daily variations in sleep length and quality impact on both mood and performance in everyday life? (iii) does age play a moderating role in the relationships between sleep, mood and performance? Sleep in 200 young (18-30 years) and 200 older adults (55-70 years) will be measured subjectively and objectively over 3 weeks in the context of their daily life. Participants will several times a day answer questions on their momentary well-being (e.g. mood, sleepiness and stress), and perform an attention task when receiving prompts on their mobile phones. A novel software application to perform the experience sampling will be developed within an interdisciplinary collaboration. The results will improve the understanding of the pivotal role of sleep for well-being and performance ability in everyday life in an ageing population.
Final report
Project aim & implementation
Previous laboratory-based studies have shown that experimental sleep deprivation impairs cognitive performance and deteriorates mood. Remarkably, these effects appeared to be less strong in older adults than in young adults. However, it remained unclear how these results translate to real-world contexts. The overarching goal of this project was to investigate the occurrence of day-to-day variations in sleep and their impact on mood and performance in everyday life and to study whether older adults respond differently than young adults to variations in sleep in everyday life.
The data collection has been successfully completed, including over 330 individuals who participated in a 21-day experience sampling method protocol. The data collection commenced in the autumn of 2022 using the PsymateTM experience sampling platform, ensuring there were no significant interferences from COVID-19 restrictions that could have otherwise substantially influenced the results. We improved the project plan in several ways during the planning phase: The number of daytime questionnaires was increased from 5 to 8, enabling us to examine not only mean levels but also dynamic aspects of positive and negative affect. We also included the cognitive performance test at each daytime measurement and added background cognitive tests.
Overall, this project has generated a uniquely valuable dataset in the field. It focuses on two adult age groups, which is still very rare in sleep research, incorporates actigraphy as an objective measure of sleep, and also includes an objective performance test. The Experience Sampling Method period lasted 21 days, making it longer than the majority of previous studies. Additionally, the study features a high frequency of daily questionnaires, including up to eight semi-randomly prompted daytime questionnaires, along with morning and evening questionnaires - significantly exceeding the frequency used in most prior research within the sleep research field.
Most important findings so far
In order to increase the transparency of the research, we have published a peer-reviewed study protocol for this study outlining methods and planned analysis strategy for the main research questions (Schwarz et al., 2023). We are now working on analysing the data and reporting the results.
Preliminary results show that sleep duration, efficiency, and quality not only vary considerably between individuals but also within individuals in both age groups. As expected, day-to-day variations in sleep duration were smaller in older adults compared to young adults. Initial analyses also suggest that intra-individual variability in sleep duration across the three weeks is associated with both depressive symptoms and indicators of positive psychological well-being, which were assessed as part of the background questionnaire, whereas average sleep duration appears to show no such association. This supports the idea that maintaining a consistent sleep duration across days is an important aspect of sleep health (Schwarz et al, in prep).
We will also analyse the impact of day-to-day variations in sleep on next-day positive and negative affect. As participants completed up to eight daily questionnaires, we aim to investigate not only mean levels of affect but also affect variability. Affect variability, which has been shown to relate to mental health, has been largely overlooked in previous studies. By examining the dynamic and fluctuating nature of both positive and negative affect, these analyses can thus provide a more comprehensive understanding of how sleep influences affective functioning.
A key question addressed in this project is whether the effect of day-to-day changes in sleep on performance in real-world contexts matches the well-established effects of experimental sleep deprivation on cognitive performance. The initial results of this study show that day-to-day variations in actigraphically measured sleep duration were associated with poorer performance on the processing speed task; specifically, individuals performed worse on days when they slept shorter than their own average sleep duration, although the effect was smaller than expected. Notably, individuals who slept shorter on average did not perform worse overall, highlighting that cross-sectional findings cannot necessarily be generalized to within-person dynamics and vice versa. The results also showed a significant impact of age group on performance in the processing speed task, suggesting that remote cognitive testing in everyday life conditions could be a viable method for investigating differences between groups that have more pronounced changes in cognitive ability. However, contrary to our hypothesis, we did not find evidence that older age moderated the impact of day-to-day variations in sleep on processing speed performance (Schwarz et al, to be submitted).
Overall, the findings so far highlight the importance of maintaining consistent sleep patterns, emphasizing the importance of day-to-day stability over simply aiming for an adequate average sleep duration.
Potential future research questions
One of the key questions addressed in this project is how sleeping less than usual affects cognitive performance on a brief objective test, with the broader aim of generating a better understanding of how sleep impacts cognition in real-world contexts. While the approach used in this project provides valuable insights, it also focuses on a narrow aspect of cognition. A key next step is to develop a more comprehensive understanding of sleep’s effects on thinking in daily life. A promising avenue forward is here to explore the impact of sleep on mind wandering, i.e. thoughts unrelated to the current task or situation—which occupies up to 50% of waking hours. Mind wandering is linked to performance, mood, creativity, and planning, with these effects being influenced by the content and quality of the thoughts. Systematically investigating how sleep, and lack thereof, impacts the occurrence of mind wandering as well as the content and quality of these wandering thoughts has the potential to greatly enhance our understanding of sleep’s role in everyday cognition.
International dimension, dissemination and collaboration
The research is strongly anchored in the international research front. We have published the study protocol, and presented the first findings from the research project at the European Sleep Research Society Conference (2024), which is the main European conference in the research field, the Nordic Congress of Gerontology (2024) and the Conference of the Swedish Cognitive Science Society (2024). Furthermore, we have established a new collaboration with a researcher from Germany, who will come to Stockholm in 2025 to work together with us using data from this project.
We intend to publish results in high-ranked international journals, which will be made accessible to the public by golden or green open access.
Previous laboratory-based studies have shown that experimental sleep deprivation impairs cognitive performance and deteriorates mood. Remarkably, these effects appeared to be less strong in older adults than in young adults. However, it remained unclear how these results translate to real-world contexts. The overarching goal of this project was to investigate the occurrence of day-to-day variations in sleep and their impact on mood and performance in everyday life and to study whether older adults respond differently than young adults to variations in sleep in everyday life.
The data collection has been successfully completed, including over 330 individuals who participated in a 21-day experience sampling method protocol. The data collection commenced in the autumn of 2022 using the PsymateTM experience sampling platform, ensuring there were no significant interferences from COVID-19 restrictions that could have otherwise substantially influenced the results. We improved the project plan in several ways during the planning phase: The number of daytime questionnaires was increased from 5 to 8, enabling us to examine not only mean levels but also dynamic aspects of positive and negative affect. We also included the cognitive performance test at each daytime measurement and added background cognitive tests.
Overall, this project has generated a uniquely valuable dataset in the field. It focuses on two adult age groups, which is still very rare in sleep research, incorporates actigraphy as an objective measure of sleep, and also includes an objective performance test. The Experience Sampling Method period lasted 21 days, making it longer than the majority of previous studies. Additionally, the study features a high frequency of daily questionnaires, including up to eight semi-randomly prompted daytime questionnaires, along with morning and evening questionnaires - significantly exceeding the frequency used in most prior research within the sleep research field.
Most important findings so far
In order to increase the transparency of the research, we have published a peer-reviewed study protocol for this study outlining methods and planned analysis strategy for the main research questions (Schwarz et al., 2023). We are now working on analysing the data and reporting the results.
Preliminary results show that sleep duration, efficiency, and quality not only vary considerably between individuals but also within individuals in both age groups. As expected, day-to-day variations in sleep duration were smaller in older adults compared to young adults. Initial analyses also suggest that intra-individual variability in sleep duration across the three weeks is associated with both depressive symptoms and indicators of positive psychological well-being, which were assessed as part of the background questionnaire, whereas average sleep duration appears to show no such association. This supports the idea that maintaining a consistent sleep duration across days is an important aspect of sleep health (Schwarz et al, in prep).
We will also analyse the impact of day-to-day variations in sleep on next-day positive and negative affect. As participants completed up to eight daily questionnaires, we aim to investigate not only mean levels of affect but also affect variability. Affect variability, which has been shown to relate to mental health, has been largely overlooked in previous studies. By examining the dynamic and fluctuating nature of both positive and negative affect, these analyses can thus provide a more comprehensive understanding of how sleep influences affective functioning.
A key question addressed in this project is whether the effect of day-to-day changes in sleep on performance in real-world contexts matches the well-established effects of experimental sleep deprivation on cognitive performance. The initial results of this study show that day-to-day variations in actigraphically measured sleep duration were associated with poorer performance on the processing speed task; specifically, individuals performed worse on days when they slept shorter than their own average sleep duration, although the effect was smaller than expected. Notably, individuals who slept shorter on average did not perform worse overall, highlighting that cross-sectional findings cannot necessarily be generalized to within-person dynamics and vice versa. The results also showed a significant impact of age group on performance in the processing speed task, suggesting that remote cognitive testing in everyday life conditions could be a viable method for investigating differences between groups that have more pronounced changes in cognitive ability. However, contrary to our hypothesis, we did not find evidence that older age moderated the impact of day-to-day variations in sleep on processing speed performance (Schwarz et al, to be submitted).
Overall, the findings so far highlight the importance of maintaining consistent sleep patterns, emphasizing the importance of day-to-day stability over simply aiming for an adequate average sleep duration.
Potential future research questions
One of the key questions addressed in this project is how sleeping less than usual affects cognitive performance on a brief objective test, with the broader aim of generating a better understanding of how sleep impacts cognition in real-world contexts. While the approach used in this project provides valuable insights, it also focuses on a narrow aspect of cognition. A key next step is to develop a more comprehensive understanding of sleep’s effects on thinking in daily life. A promising avenue forward is here to explore the impact of sleep on mind wandering, i.e. thoughts unrelated to the current task or situation—which occupies up to 50% of waking hours. Mind wandering is linked to performance, mood, creativity, and planning, with these effects being influenced by the content and quality of the thoughts. Systematically investigating how sleep, and lack thereof, impacts the occurrence of mind wandering as well as the content and quality of these wandering thoughts has the potential to greatly enhance our understanding of sleep’s role in everyday cognition.
International dimension, dissemination and collaboration
The research is strongly anchored in the international research front. We have published the study protocol, and presented the first findings from the research project at the European Sleep Research Society Conference (2024), which is the main European conference in the research field, the Nordic Congress of Gerontology (2024) and the Conference of the Swedish Cognitive Science Society (2024). Furthermore, we have established a new collaboration with a researcher from Germany, who will come to Stockholm in 2025 to work together with us using data from this project.
We intend to publish results in high-ranked international journals, which will be made accessible to the public by golden or green open access.