Word count (excluding title, name and introduction): 1057
Word count (including title, name and introduction): 1099
DOES CEREBROVASCULAR REACTIVITY DECLINE WITH AGE?
From the assessment of 45 healthy adults with FNIRS it was found that 1) CVR was
negatively associated with age 2) increasing age was associated with widespread
coactivation within the prefrontal and sensorimotor regions.
Ageing exposes the brain to chemical, structural, electrophysiological and molecular
changes. As a consequence, the brain’s function changes with age [1]. Age related
functional changes involves a decline in working memory, cognitive function,
cognitive control and general processing speed [2].
Ageing is associated with an increased risk of developing neurodegenerative
diseases, cerebrovascular disease, and dementia [3,4]. It is significantly positively
correlated with the presence of hippocampal atrophy, cerebral microbleeds and
white matter hyperintensity in participants without cerebrovascular risk factors [5].
Thus, explaining the prevalence of the previously mentioned diseases in the elderly
population.
A 1989 rat model [6] found minor but selective changes in GABAnergic and
Cholinergic markers in ageing brains. Furthermore, they found that the vessel’s
contractile response to Prostaglandin F2α and 5-Hydroxytryptomine reduces with
age. However, the basilar artery was spared and had a relatively normal vasomotor
function. As this is an outdated rat model, it may not be applicable to the current
human population however, it does give an insight into why cerebrovascular activity
(CVR) may change with age [7, 8, 9, 10]. CVR, is the brain’s ability to maintain
perfusion and meet metabolic demands in response to changes in oxygen and
carbon dioxide levels [11]. It is hypothesised that CVR declines with age.
A previous experiment studied healthy adults and found that CVR is significantly
decreased in the white matter of the frontal region, specifically in the anterior
cerebral artery and middle cerebral artery water-shed area [7]. Another study [8] on
healthy adults found that the temporal lobe had the quickest longitudinal age-related
CVR reduction, followed by the parietal then frontal and occipital lobes. This was
further supported by a study [9], that found that hypercapnia-induced cerebral blood
flow responses, were lower in the older group, implying an age-related reduction in
CVR. Therefore, it is evident that age-related CVR decline is present and occurs
globally.
These findings however, have been contraindicated by previous studies, for
example, one study [10] did not find an age-related CVR decline, instead they found
a positive correlation between CVR and age in the posterior cerebral arteries of
migraine patients. It is important to note that, the studies previously mentioned only
included healthy volunteers unlike this study. So, it is possible that the
pathophysiology of migraine may have accounted for this finding.
Overall, we could safely assume that majority of literature is in support of the idea
that CVR reduces with age in individuals with no prior cerebrovascular or
neurological diseases.
Here, Karunakaran et al., also demonstrates a negative correlation between ageing
and CVR within the prefrontal and sensorimotor cortex, using a functional near-
infrared spectroscopy (FNIRS). FNIRS, detects changes in neural activity within the
brain by penetrating the brain tissue with near-infrared light [12].
Word count (including title, name and introduction): 1099
DOES CEREBROVASCULAR REACTIVITY DECLINE WITH AGE?
From the assessment of 45 healthy adults with FNIRS it was found that 1) CVR was
negatively associated with age 2) increasing age was associated with widespread
coactivation within the prefrontal and sensorimotor regions.
Ageing exposes the brain to chemical, structural, electrophysiological and molecular
changes. As a consequence, the brain’s function changes with age [1]. Age related
functional changes involves a decline in working memory, cognitive function,
cognitive control and general processing speed [2].
Ageing is associated with an increased risk of developing neurodegenerative
diseases, cerebrovascular disease, and dementia [3,4]. It is significantly positively
correlated with the presence of hippocampal atrophy, cerebral microbleeds and
white matter hyperintensity in participants without cerebrovascular risk factors [5].
Thus, explaining the prevalence of the previously mentioned diseases in the elderly
population.
A 1989 rat model [6] found minor but selective changes in GABAnergic and
Cholinergic markers in ageing brains. Furthermore, they found that the vessel’s
contractile response to Prostaglandin F2α and 5-Hydroxytryptomine reduces with
age. However, the basilar artery was spared and had a relatively normal vasomotor
function. As this is an outdated rat model, it may not be applicable to the current
human population however, it does give an insight into why cerebrovascular activity
(CVR) may change with age [7, 8, 9, 10]. CVR, is the brain’s ability to maintain
perfusion and meet metabolic demands in response to changes in oxygen and
carbon dioxide levels [11]. It is hypothesised that CVR declines with age.
A previous experiment studied healthy adults and found that CVR is significantly
decreased in the white matter of the frontal region, specifically in the anterior
cerebral artery and middle cerebral artery water-shed area [7]. Another study [8] on
healthy adults found that the temporal lobe had the quickest longitudinal age-related
CVR reduction, followed by the parietal then frontal and occipital lobes. This was
further supported by a study [9], that found that hypercapnia-induced cerebral blood
flow responses, were lower in the older group, implying an age-related reduction in
CVR. Therefore, it is evident that age-related CVR decline is present and occurs
globally.
These findings however, have been contraindicated by previous studies, for
example, one study [10] did not find an age-related CVR decline, instead they found
a positive correlation between CVR and age in the posterior cerebral arteries of
migraine patients. It is important to note that, the studies previously mentioned only
included healthy volunteers unlike this study. So, it is possible that the
pathophysiology of migraine may have accounted for this finding.
Overall, we could safely assume that majority of literature is in support of the idea
that CVR reduces with age in individuals with no prior cerebrovascular or
neurological diseases.
Here, Karunakaran et al., also demonstrates a negative correlation between ageing
and CVR within the prefrontal and sensorimotor cortex, using a functional near-
infrared spectroscopy (FNIRS). FNIRS, detects changes in neural activity within the
brain by penetrating the brain tissue with near-infrared light [12].
