Heart rate and blood pressure decreases after a motor task in pre‐symptomatic AD: Biomarkers (non‐neuroimaging)/Differential diagnosis

Background

Understanding how cardiovascular health affects the early Alzheimer’s disease (AD) pathology is challenging because several variables can contribute to significant changes in blood pressure (BP) and heart rate (HR). Previous studies have suggested an association between Alzheimer's disease and HR. Little association is known about pre-symptomatic AD. We aim to explore the HR and BP changes before and after a motor task in a cognitive healthy population.

Method

Participants (age ranged 61-95 years old) were recruited from the local community, including cognitively healthy (CH) individuals who were further subdivided based on cerebrospinal fluid (CSF) classification: those with a normal amyloid/tau ratio (CH-NAT, n = 11) or a pathological amyloid/tau ratio (CH-PAT, n = 8). Two groups were age, gender, BMI, and education matched. Participants were asked to use a steering wheel to follow a moving line presented on the monitor. Practice session were followed by three task-identical sessions, 90 seconds per session. Each session consisted of 3 repeated blocks, 30 seconds per block: bump, trail, and bump & trail. Systolic pressure (SP), diastolic pressure (DP), pulse pressure (PP), and HR were measured before and after completing the whole task.

Result

No differences in BP and HR were found between CH-NATs and CH-PATs. We found a significant decrease in SP for both CH-NATs (pre-task 135.2±24.2, post-task 127.2±18.8, reduced by 8±9.7, p = 0.0208) and CH-PATs (pre-task: 146.1±20.6, post-task: 134.8±19.6, reduced by 11.3±5.2, p = 0.0004). Furthermore, CH-PATs have a significant drop in HR (pre-task: 71.4±10.7, post-task: 66.3±8.2, reduced by 5.1±4.1 beats, p = 0.0098) compared to CH-NATs (pre-task: 70.8±11.8, post-task: 69.2±13.3, reduced by 1.5±6.2 beats, p = 0.4302). CH-PATs has decreased HR*SP (pre-task: 10464±2375.6, post-task: 8941.1±1843.1, reduced by 1522.9±775.8, p = 0.0009), compared to CH-NATs (pre-task: 9537.2±2098.3, post-task: 8765.2±1769.2, reduced by 772.0±1153.5, p=0.0507). No significant change was found in DP for either CH-NATs or CH-PATs.

Conclusion

Pre-symptomatic AD participants have a significant drop of HR, SP, and SP*HR compared to CH-NATs, indicating reduced sympathetic responses after motor task. These changes in HR and SP may provide evidence of compromised cardiovascular health and autonomic regulation in pre-symptomatic AD.