ABSTRACT
Alzheimer’s Disease and Related Dementias (ADRD) is an emerging epidemic in the United States; Black
adults are particularly vulnerable. Without effective prevention strategies to target and optimize resilience to
ADRD, 14 million U.S. adults will be living with ADRD by 2060, with an associated financial burden of $511
billion by 2040. While physical activity has been consistently identified as a modifiable, protective factor to
prevent cognitive decline and delay age of dementia onset, the majority of this evidence is based on reported
estimates of leisure-time moderate to vigorous intensity physical activity (MVPA), which provides an
incomplete characterization of this complex behavioral phenotype. Adults spend approximately 95% of waking
hours sedentary or in light intensity physical activity; however, there is limited research exploring the
interrelations of these different intensity categories. Further, less than 10% of adults accumulate sufficient
MVPA to meet recommendations, and this prevalence estimate is even lower in Black adults. Studies have
also demonstrated that sleep disturbances, including short sleep duration, circadian rhythm disturbances, and
sleep-disordered breathing may increase risk of cognitive impairment. However, this evidence is still emerging.
Further, Black adults have a higher prevalence of disordered sleep compared to Whites. Despite the potential
importance of both waking and sleep behaviors to optimize cognitive resilience, their impacts are often studied
in isolation. To address these critical research gaps, we propose the Jackson Heart Study (JHS) 24-Hour
Activity Cycle Study (Jackson 24H-ACT), a four-year ancillary study to the funded JHS Exam 4 (2020-22). The
overall goal of the Jackson 24H-ACT Study is to quantify 24-hour activity cycle behaviors and estimate the
independent and joint roles of waking (sedentary to vigorous intensity physical activity) and sleep (duration and
quality characteristics) behaviors to optimize cognitive resilience. All participants attending Exam 4 and who
are willing to concurrently wear an accelerometer and sleep actigraphy watch for seven consecutive days will
be invited to participate. Exclusion criteria include: unable to ambulate or physician instruction not to be
physically active. Jackson 24H-ACT ancillary study measures include: (1) accelerometry and (2) sleep
actigraphy, which complement extant JHS data, and data that will be collected as part of Exam 4. To
accomplish these goals, we propose to examine the independent and joint associations of 24-hour activity
cycle behaviors with: (Aim 1) cognitive functioning; (Aim 2) subclinical markers of cerebrovascular disease
(e.g. white matter hyperintensity volumes), white matter microstructural integrity, and neurodegeneration (e.g.
hippocampal and total brain volumes) quantified from brain magnetic resonance (MRI) imaging; and (Aim 3)
the prevalence of mild cognitive impairment (MCI) and dementia. Potential moderation by sex, age epoch (<65
versus =65 years), education/literacy, and APOE ¿4 genotype will also be evaluated. Jackson 24H-ACT will
provide novel information on the role of 24-hour activity cycles in promoting cognitive resilience in Black adults.
