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Dissertation
Rest-activity rhythm, positive affect, and cognitive function in older adults
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2025
DOI: 10.25820/etd.007864
Abstract
Over the next four decades, the aging population in the U.S. is projected to double, reaching an estimated 80 million by 2040 (Vincent, 2010). Cognitive decline with aging can affect social relationships, increase safety concerns, and burden caregivers (Livingston et al., 2017). Research shows that good sleep, less sedentary behavior, and regular physical activity benefit cognitive health by improving cerebral blood flow and neural growth (Ohayon & Vecchierini, 2005; Zhang et al., 2013). Rest-Activity Rhythm (RAR) elucidates this 24-hour pattern of sleep and activity (Smagula, 2016). However, a gap in our understanding is the relationship between RAR and cognitive function in older adults. Thus, this doctoral dissertation comprises three separate papers aimed at elucidating this gap.
The first paper undertakes a systematic review to synthesize existing literature regarding the relationship between RAR and cognitive function in older adults. We also propose an integrative framework to inform the development of future research studies. Although it was difficult to draw definitive conclusions in this literature review due to the limited number of available studies focusing on each cognitive domain and methodological heterogeneity among them, the collective findings broadly indicate that later peak activity timing, higher mean activity levels, higher activity amplitude, and more stable rhythmicity were associated with better global cognition. Further research should be undertaken using large and diverse samples, prospective designs, comprehensive and well validated measurements, and comprehensively account for confounding variables.
The second paper presents a secondary analysis examining the association between RAR and cognitive performance among older adults. Utilizing a sample of fifty-seven community-dwelling older adults, participants (mean age ± standard deviation: 70±7.3 years) wore Actiwatch Spectrum Plus devices for two weeks while undergoing a comprehensive neuropsychological battery assessment. Multiple linear regression modeling was used to examine associations between different RAR parameters and each cognitive domain. Our findings provide evidence that mean activity level was associated with processing speed after adjustment for covariates (β=11.68, p<0.05). RAR rhythmicity was associated with immediate memory (β=2.94, p<0.05) and memory recall (β=3.83, p<0.05) in adjusted models. Further research should be undertaken using a large and diverse sample and prospective design to confirm those associations.
The third paper examines the associations between positive affect and RAR in older adults. Using data from 308 participants in Midlife Development in the United States (MIDUS II) study, this paper explores how positive affect correlates with key RAR parameters: mesor (average activity level), amplitude (maximum activity level), acrophase (timing of maximum activity level), and R-square (a measure of rhythmicity). The study found significant positive associations between higher positive affect and improved RAR parameters, including mesor (β = 16.177, p=0.032), amplitude (β= 18.456, p=0.015), and R-square (β = 0.031, p=0.011). Income was found to significantly moderate the relationship between positive affect and mesor (interaction term β = 30.674, p < 0.05). Specifically, the association between positive affect and mesor was stronger among individuals with higher income, indicating that higher income amplified the positive relationship between affect and activity levels. In contrast, neither age nor self-reported health significantly moderated these associations. These findings suggest that positive affect influences RAR and highlights potential areas for intervention aimed at improving health and well-being through enhancing positive emotions in older adults. Furthermore, the potential for a bidirectional association between positive affect and RAR cannot be ruled out.
This research contributes to the burgeoning field of gerontology and cognitive science by providing a deeper understanding of how RAR are associated with cognitive function in older adults and how positive affect are linked to RAR. The findings have significant implications for developing interventions to maintain or improve cognitive health in older adults.
Details
- Title: Subtitle
- Rest-activity rhythm, positive affect, and cognitive function in older adults
- Creators
- Meina Zhang
- Contributors
- Chooza Moon (Advisor)Sue E Gardner (Committee Member)Kara M Whitaker (Committee Member)Nai-Ching Chi (Committee Member)Boxiang Wang (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Nursing
- Date degree season
- Spring 2025
- DOI
- 10.25820/etd.007864
- Publisher
- University of Iowa
- Number of pages
- xii, 106 pages
- Copyright
- Copyright 2025 Meina Zhang
- Language
- English
- Date submitted
- 04/16/2025
- Description illustrations
- illustrations, tables, graphs
- Description bibliographic
- Includes bibliographical references (pages 83-102).
- Public Abstract (ETD)
- This dissertation examines the impact of Rest-Activity Rhythm (RAR)—the daily pattern of sleep and activity—and its association with positive affect and cognitive function in older adults. As the global population ages, understanding factors that influence cognitive health is increasingly important. This research explores how sleep-activity patterns relate to cognitive functions, such as memory, attention, and problem-solving, and how positive affect is associated with RAR. The study finds that older adults with more stable and structured daily sleep-activity patterns tend to remember things more quickly and easily. Additionally, individuals with higher levels of positive affect tend to have more consistent RAR. These findings suggest that maintaining regular sleep and activity habits, alongside fostering positive emotions, may contribute to overall well-being and cognitive health in aging populations. The findings highlight that simple lifestyle modifications—such as adhering to a stable sleep and activity schedule—may support cognitive health. These insights are relevant for designing interventions aimed at promoting healthy aging and brain health. In summary, this dissertation emphasizes the significance of daily sleep-activity patterns in relation to cognitive function, as well as the potential role of positive affect in shaping RAR. The result provides insights that could help guide lifestyle interventions aimed at promoting cognitive health in aging populations.
- Academic Unit
- Nursing
- Record Identifier
- 9984831231402771
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