The Importance of Stable Blood Pressure in Aging

In a recent study led by researchers from the University of South Australia (UniSA), scientists have uncovered the profound impact of fluctuating blood pressure on the cognitive health of older individuals, shedding light on the connection between blood pressure variations and the risk of dementia and vascular issues in the elderly. 

High blood pressure is well-known as a risk factor for dementia, but the study underscores the importance of addressing the often-overlooked issue of fluctuating blood pressure in clinical treatments.

To understand the mechanisms connecting blood pressure fluctuations with dementia, the researchers recruited 70 healthy older adults, aged 60-80, without cognitive impairment. They carefully monitored participants' blood pressure, conducted cognitive tests, and employed specialized techniques to measure arterial stiffness in the brain and arteries.

The study unveiled a striking revelation: higher blood pressure variability, whether within a single day or across multiple days, was strongly associated with reduced cognitive performance. This is particularly evident in older adults with high mid-term blood pressure variability (BPV), leading to diminished executive functioning. Furthermore, fluctuations in systolic blood pressure were found to correlate with increased arterial stiffness, suggesting that various types of blood pressure variability may stem from distinct underlying biological mechanisms. The variations observed extend well beyond the typical, minor fluctuations observed during circadian rhythms and changes in position, surpassing 20% of systolic blood pressure. 

These findings have significant implications, indicating that monitoring blood pressure variability could serve as an early clinical marker or a treatment target to prevent cognitive impairment.

In addition, the study discovered that higher short-term BPV is linked to decreased attention and psychomotor speed, and these associations persist independently of mean blood pressure, age, and antihypertensive treatment. The impact of BPV on cognition and vascular stiffness surpasses that of circadian and mean blood pressure.

Notably, systolic short-term BPV demonstrates a positive correlation with arterial stiffness in older adults without dementia. During sleep, systolic and diastolic blood pressure usually exhibit a 10-20% decline, referred to as 'dipping.' However, abnormal nocturnal blood pressure changes fall into three categories: 'extreme-dippers' (>20%), 'non-dippers' (<10%), and 'reverse-dippers' (indicating an increase instead of a decrease in nocturnal BP).

The average short-term (24-hour) and day-to-day blood pressure levels among the participants fall within the normal category (non-hypertensive). Among those with available data on night-time dipping, 60% are categorized as normal, 15% as extreme dippers, 22% as non-dippers, and 3% as reverse dippers.

The study highlights that morning systolic BPV, assessed via ARV (average real variability), is significantly and positively correlated with three cognitive assessment outcomes, including one from the Reaction Time Task and two from the Spatial Working Memory Task.

It's important to acknowledge two significant challenges that the authors did not directly address in this study. The first pertains to the sample size, consisting of 70 patients from a single city in Australia. The second lies in the timeframe during which the study was conducted, spanning from 2020 to 2022. This period witnessed acute psychological distress, intense stress, fear, illness, and substantial disruptions in daily routines, all of which can potentially amplify blood pressure variability, disturb circadian rhythms, and impact overall well-being.

REFERENCE

Gutteridge DS, Tully PJ, Smith AE, Loetscher T, Keage HA. Cross-sectional associations between short and mid-term blood pressure variability, cognition and vascular stiffness in older adults. Cereb Circ Cogn Behav. 2023 Sep 1;5:100181. doi: 10.1016/j.cccb.2023.100181. PMID: 37711969; PMCID: PMC10497990.

PS In a more recent study of 13,447 Chinese adults (including 14.6% centenarians), age was positively associated with SBP in robust hypertensive elderly but negatively associated with it in frail hypertensive elderly. SBP < 120 mmHg was the risk factor of mortality among the frail oldest-old (≥85 years) while SBP ≥ 150 mmHg was that among the robust young-old (65-84 years). DBP ≥ 90 mmHg was the risk factor of mortality both in the robust young-old and the frail oldest old. 

REFERENCE

Wang HY, Wang J, Wang Q, Yang C, Huang Y, Chen M. Blood pressure in the longevous population with different status of hypertension and frailty. Hypertens Res. 2023 Nov 20. doi: 10.1038/s41440-023-01499-1. Epub ahead of print. PMID: 37985739.