0417 Associations Between Rest-Activity Patterns and Resting-State Networks in Older Adults

Introduction

Resting-state functional connectivity is coherent brain activity in a task-free state that strongly correlates to task-evoked sensory, motor, and higher-order cognitive systems. Certain networks show decreased functional connectivity with aging. Aging is associated with changes in circadian rhythms and sleep-wake cycles. Limited research has been conducted on how circadian activity and sleep are related to markers of functional brain aging. The purpose of this study was to explore whether rest-activity patterns and shorter sleep duration are related to functional connectivity of specific resting-state networks in older adults.

Methods

A total of 124 cognitively normal participants (mean age (SD) = 67.2 (5.7), 42% men) underwent 3.0 T MRI and week-long wrist actigraphy protocols. Rest-activity pattern was analyzed using an extended cosine model calculating acrophase (time of peak activity) and pseudo-F statistics of goodness-of-fit (a measure of overall rhythmicity). We used resting-state fMRI scans to measure functional connectivity in association and sensory networks as defined by the Schaefer 17 network functional atlas. Multiple linear regression analysis was used to investigate how rest-activity pattern parameters and sleep duration are associated with resting-state functional connectivity, adjusting for age, sex, and sleep apnea.

Results

We found that the average acrophase was 2:30 PM (SD = 54 min), and delayed acrophase (average vs. delayed [+1SD]) was associated with lower functional connectivity of the right-lateralized default mode network A (p=0.02), and higher pseudo-F statistics was associated with higher functional connectivity in networks including left dorsal attention B (p=0.001), right somatomotor A (p = 0.05), and somatomotor B (both p=0.02). Longer sleep duration was associated with higher right executive control B (p=0.03).

Conclusion

The overall rhythmicity of diurnal rest-activity patterns and longer sleep duration are associated with some resting-state functional networks. Further investigation is needed to understand the mechanisms between circadian rhythm and brain function.

Support

National Institute of Health, U of Iowa Aging Mind Brain Initiative, Center on Aging

Replacing sedentary time with sleep, light, or moderate-to-vigorous physical activity: effects on self-regulation and executive functioning

Recent attention has highlighted the importance of reducing sedentary time for maintaining health and quality of life. However, it is unclear how changing sedentary behavior may influence executive functions and self-regulatory strategy use, which are vital for the long-term maintenance of a health behavior regimen. The purpose of this cross-sectional study is to examine the estimated self-regulatory and executive functioning effects of substituting 30 min of sedentary behavior with 30 min of light activity, moderate-to-vigorous physical activity (MVPA), or sleep in a sample of older adults. This study reports baseline data collected from low-active healthy older adults (N = 247, mean age 65.4 ± 4.6 years) recruited to participate in a 6 month randomized controlled exercise trial examining the effects of various modes of exercise on brain health and function. Each participant completed assessments of physical activity self-regulatory strategy use (i.e., self-monitoring, goal-setting, social support, reinforcement, time management, and relapse prevention) and executive functioning. Physical activity and sedentary behaviors were measured using accelerometers during waking hours for seven consecutive days at each time point. Isotemporal substitution analyses were conducted to examine the effect on self-regulation and executive functioning should an individual substitute sedentary time with light activity, MVPA, or sleep. The substitution of sedentary time with both sleep and MVPA influenced both self-regulatory strategy use and executive functioning. Sleep was associated with greater self-monitoring (B = .23, p = .02), goal-setting (B = .32, p < .01), and social support (B = .18, p = .01) behaviors. Substitution of sedentary time with MVPA was associated with higher accuracy on 2-item (B = .03, p = .01) and 3-item (B = .02, p = .04) spatial working memory tasks, and with faster reaction times on single (B = -23.12, p = .03) and mixed-repeated task-switching blocks (B = -27.06, p = .04). Substitution of sedentary time with sleep was associated with marginally faster reaction time on mixed-repeated task-switching blocks (B = -12.20, p = .07) and faster reaction time on mixed-switch blocks (B = 17.21, p = .05), as well as reduced global reaction time switch cost (B = -16.86, p = .01). Substitution for light intensity physical activity did not produce significant effects. By replacing sedentary time with sleep and MVPA, individuals may bolster several important domains of self-regulatory behavior and executive functioning. This has important implications for the design of long-lasting health behavior interventions. Trial Registration clinicaltrials.gov identifier NCT00438347.

White matter integrity, hippocampal volume, and cognitive performance of a world-famous nonagenarian track-and-field athlete

Physical activity (PA) and cardiorespiratory fitness (CRF) are associated with successful brain and cognitive aging. However, little is known about the effects of PA, CRF, and exercise on the brain in the oldest-old. Here we examined white matter (WM) integrity, measured as fractional anisotropy (FA) and WM hyperintensity (WMH) burden, and hippocampal (HIPP) volume of Olga Kotelko (1919-2014). Olga began training for competitions at age of 77 and as of June 2014 held over 30 world records in her age category in track-and-field. We found that Olga's WMH burden was larger and the HIPP was smaller than in the reference sample (58 healthy low-active women 60-78 years old), and her FA was consistently lower in the regions overlapping with WMH. Olga's FA in many normal-appearing WM regions, however, did not differ or was greater than in the reference sample. In particular, FA in her genu corpus callosum was higher than any FA value observed in the reference sample. We speculate that her relatively high FA may be related to both successful aging and the beneficial effects of exercise in old age. In addition, Olga had lower scores on memory, reasoning and speed tasks than the younger reference sample, but outperformed typical adults of age 90-95 on speed and memory. Together, our findings open the possibility of old-age benefits of increasing PA on WM microstructure and cognition despite age-related increase in WMH burden and HIPP shrinkage, and add to the still scarce neuroimaging data of the healthy oldest-old (>90 years) adults.

Aerobic fitness is associated with greater efficiency of the network underlying cognitive control in preadolescent children

This study examined whether individual differences in aerobic fitness are associated with differences in activation of cognitive control brain networks in preadolescent children. As expected, children performed worse on a measure of cognitive control compared with a group of young adults. However, individual differences in aerobic fitness were associated with cognitive control performance among children. Lower-fit children had disproportionate performance cost in accuracy with increasing task difficulty, relative to higher-fit children. Brain activation was compared between performance-matched groups of lower- and higher-fit children. Fitness groups differed in brain activity for regions associated with response execution and inhibition, task set maintenance, and top-down regulation. Overall, differing activation patterns coupled with different patterns of brain-behavior correlations suggest an important role of aerobic fitness in modulating task strategy and the efficiency of neural networks that implement cognitive control in preadolescent children.

Air travel for the chronically ill and the elderly

The cabin altitude during airline flights is usually 1,500 m (5,000 ft). Medically important factors include the decreased bioavailability of oxygen, the dryness of the air and the properties of gases within the body as stated in Boyle's law. Passengers who are physically compromised by chronic disease, advanced age or mobility impairment can usually have their special requirements met through the cooperation of the family physician and the airline. Special diets, supplemental oxygen, locomotive aids and communication services are provided on advanced request.