Higher blood pressure at night may be a risk factor for Alzheimer’s disease


Higher blood pressure at night than in daytime may be a risk factor for Alzheimer’s disease in older men.

This is suggested by a new study from researchers at Uppsala University, now published in the journal Hypertension.

‘Dementia’ is an umbrella term used to describe a category of symptoms marked by behavioural changes and gradually declining cognitive and social abilities. Numerous factors, including hypertension (high blood pressure), affect the risk of developing these symptoms.

Under healthy conditions, blood pressure (BP) varies over 24 hours, with lowest values reached at night. Doctors call this nocturnal blood pressure fall ‘dipping’. However, in some people, this BP pattern is reversed: their nocturnal BP is higher than in daytime. This blood pressure profile is known as ‘reverse dipping’.

“The night is a critical period for brain health. For example, in animals, it has previously been shown that the brain clears out waste products during sleep, and that this clearance is compromised by abnormal blood pressure patterns.

Since the night also represents a critical time window for human brain health, we examined whether too high blood pressure at night, as seen in reverse dipping, is associated with a higher dementia risk in older men,” says Christian Benedict, Associate Professor at Uppsala University’s Department of Neuroscience, and senior author of the study.

To test this hypothesis, the researchers used observational data from one thousand Swedish older men, who were followed for a maximum of 24 years. The included men were in their early seventies at the beginning of the study

“The risk of getting a dementia diagnosis was 1.64 times higher among men with reverse dipping compared to those with normal dipping. Reverse dipping mainly increased the risk of Alzheimer’s disease, the most common form of dementia,” says Xiao Tan, postdoctoral fellow from the same department and first author of this research.

“Our cohort consisted only of older men. Thus, our results need to be replicated in older women,” concludes Benedict.

According to the researchers, an interesting next step would be to investigate whether the intake of antihypertensive (BP-lowering) drugs at night can reduce older men’s risk of developing Alzheimer’s disease.

Alzheimer’s disease (AD) is a neurodegenerative disorder of elderly individuals and is characterized by the accumulation of β-amyloid and tau in brain, progressive brain atrophy, and cognitive decline [1]. With the increase of life expectancy in developed countries, the incidence of AD and its socioeconomic impact are also growing [2].

Currently, there is no preventive or disease-modifying therapeutic measures, therefore identification of modifiable risk factors is required. The well-established AD biomarkers include cerebrospinal fluid (CSF) biomarkers of β-amyloid 42 (Aβ42), total tau (T-tau), and phosphorylated tau (P-tau); positron emission tomography (PET) measurements of Aβ and tau; and structural magnetic resonance imaging (MRI) measurements [3–5], which are increasingly used to support the diagnosis of AD in research, clinical practice and drug development and have become part of the newly revised early diagnostic criteria for AD [6, 7].

Therefore, it is necessary to investigate the associations between susceptibility factors and biomarkers in the preclinical stage of AD, which is helpful for early identification of modifiable factors.

Pulse pressure (PP) is an index of vascular aging and displays a linear increase with age [8]. It has also been recognized as a marker of increased arterial stiffness and widespread atherosclerosis. Atherosclerosis and cerebrovascular diseases have been implicated in the occurrence and development of AD [9, 10].

Therefore, it is biologically plausible to suppose that high pulse pressure could be related to the development of AD [11]. Several relevant studies indicated that high PP was associated with AD pathophysiology [8, 12–14], suggesting that vascular aging might increase AD risk [11].

Some studies suggested PP elevation was associated with CSF P-tau and Aβ42 in cognitively normal older adults [8]. Others found arterial stiffness was associated with Aβ plaque deposition in the brain [15]. Furthermore, previous studies indicated arterial stiffness might play a role in early cognitive decline and brain atrophy in mid-to-late life [13, 14, 16].

However, these studies were mostly limited by their cross-sectional design and small samples, and the mechanisms underlying the association between PP and AD were still unclear.

More studies are warranted to explore whether PP might increase AD risk or not. This study was designed to investigate whether PP was related to baseline and longitudinal changes in AD biomarkers such as CSF biomarkers, cortical amyloid-beta load, MRI measurements and neuropsychological composites in a large sample of non-demented elderly from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) study.

reference link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7585106/

Original Research: Closed access.
Reverse Dipping of Systolic Blood Pressure Is Associated With Increased Dementia Risk in Older Men: A Longitudinal Study Over 24 Years” by Christian Benedict et al. Hypertension



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