Blood pressure is dynamically regulated in response to circumstances and circadian rhythm. One of the issues arising with age is that this regulation is impaired, such as by the various mechanisms that stiffen blood vessels that include altered behavior of smooth muscle cells and cross-linking of the extracellular matrix. Researchers here show that dysregulation of diastolic blood pressure, in which normal variability is suppressed, can be distinctly correlated to progression of age-related cognitive decline. This is likely a reflection of shared underlying mechanisms that lead to both varied forms of vascular dysfunction in the brain and systemic dysregulation of blood pressure throughout the body.
Blood pressure variability (BPV) refers to the degree to which blood pressure fluctuates within a given time frame. Previous studies have shown a clear association between BPV and cerebral small-vessel disease (CSVD). BPV is strongly associated with the risk of developing CSVD and its severity, and systolic BPV (SBPV) has been shown to be positively associated with the incidence of cerebral white matter lesions, stroke, and cognitive decline. SBPV leads to unstable cerebral perfusion, which may result in chronic underperfusion or intermittent overperfusion, both of which can impair brain microstructure and function over time. This instability exacerbates the effects of CSVD, a key pathological substrate for vascular cognitive dysfunction, leading to lacunar infarcts, microhemorrhages, and diffuse white matter lesions, all of which are associated with cognitive impairment.
However, the above studies have focused on the effect of SBPV on CSVD, whereas the significant effect of diastolic BPV (DBPV) on CSVD is rarely reported. The interplay between DBPV and cognitive functions is multifaceted at the age where diastolic pressure is starting to decline. This complexity in variability may stem from the process of vascular aging, which is influenced by unique, individual factors not necessarily aligned with chronological age. After adjusting for multiple comparisons, it was found that a larger early and late-phase DBPV is associated with declines in attention tasks and psychomotor tasks, as well as a greater volume of white matter hyperintensities on imaging. It is generally accepted that DBPV fluctuations decrease with age, influenced by vascular aging.
A total of 383 CSVD patients were included in this study. Patients with CSVD were divided into 4 groups based on the Mini-Mental State Examination (MMSE) to compare the differences between these groups. AI = (blood total cholesterol - high-density lipoprotein cholesterol [HDL-C]) ÷ HDL-C; DBPV = standard deviation of 24-hour DBP. A logistic regression model was constructed to screen out the risk factors for cognitive dysfunction in patients with CSVD, and the model was evaluated using the receiver operating characteristic curve.
Patients with different degrees of cognitive dysfunction revealed differences in 24-hour mean diastolic blood pressure (DBP), DBPV, daytime DBP, nocturnal systolic blood pressure, and nocturnal drop in systolic blood pressure and DBP between the groups. Notably, the variability in DBP is significantly lower in the mild and moderate cognitive dysfunction groups compared to the normal cognitive function group. Additionally, the arterial stiffness index negatively correlates with cognitive decline, while showing a positive correlation with the 24-hour average DBPV. In other words, individuals with lower variability of DBP exhibited higher AI and poorer cognitive functions, emphasizing the importance of diastolic pressure stability in maintaining cognitive health. Unlike previous studies that mainly focused on the impact of systolic pressure on cognitive function, our findings suggest that variability in diastolic pressure may be an overlooked risk factor for cognitive decline.
Link: https://doi.org/10.1097/MD.0000000000044190
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