Low ankle-brachial index tied to CeVD markers, poor verbal memory in Singaporeans
A low ankle-brachial index (ABI) is significantly associated with magnetic resonance imaging (MRI) markers of cerebrovascular disease (CeVD), including intracranial stenosis and lacunar infarcts, in an elderly Singaporean population, a new study reveals.
“Furthermore, low ABI was associated with reduced performance in verbal memory. However, this association was attenuated in the presence of large and small vessel diseases and neurodegeneration,” researchers said.
A low ABI was significantly associated with cortical infarcts (odds ratio [OR], 1.48; 95 percent CI, 1.04 to 2.11), intracranial stenosis (OR, 1.51; 1.23 to 1.87) and lacunar infarcts (OR, 1.29; 1.06 to 1.57; p<0.05 for all) after adjusting for age and gender. [Atherosclerosis 2017;263:272-277]
On the other hand, additional adjustments for ethnicity, hypertension, diabetes and hyperlipidaemia showed that low ABI remained associated with only intracranial stenosis (OR, 1.53; 1.23 to 1.90) and lacunar infarcts (OR, 1.26; 1.03 to 1.53; p<0.05 for both).
Further adjustments for individual MRI markers showed consistent significant relationship with intracranial stenosis and lacunar infarcts (p<0.05 for both).
“By utilizing a larger study population, the present study demonstrates a low ABI to be independently associated with lacunar infarcts in addition to the previously reported association with intracranial stenosis in a Singaporean Chinese population,” said researchers. [Neuroepidemiology 2014;42:131-138]
Lower global cortical thickness was significantly associated with low ABI scores even after adjusting for intracranial volume (β, 0.08;0.10 to 0.14; p=0.024) and white matter hyperintensity volume (WMH; β, 0.07; 0.01 to 0.14; p=0.027).
Cortical thickness in specific lobes like the limbic (β, 0.09; 0.02 to 0.15; p=0.012), temporal (β, 0.07; 0.01 to 0.14; p=0.026), parietal (β, 0.07; 0.00 to 0.13; p=0.042) and occipital (β,0.07; 0.01 to 0.14; p=0.031) lobes were also significantly associated with low ABI after adjusting for intracranial volume.
Cortical thickness in the parietal lobe did not remain significantly correlated with ABI after controlling for intracranial stenosis (β, 0.06; -0.01 to 0.13; p=0.068) and lacunar infarcts (β, 0.06; -0.00 to 0.13; p=0.061).
These findings suggest that a low ABI may also be indicative of neurodegeneration as measured by cortical thickness, the investigators said.
“Possible mechanisms may be attributed to a decrease in overall cerebral perfusion due to atherosclerosis that eventually triggers several pathological changes including infarcts and neurodegeneration,” they added.
Low ABI was significantly associated with verbal memory (β, 0.06; 0.00 to 0.11; p=0.036) but not with global cognitive performance (β, 0.04; -0.01 to 0.08; p=0.099) after adjusting for age, gender, ethnicity and comorbid conditions.
Notably, after adjusting for MRI markers, low ABI did not remain significantly correlated with verbal memory (β, 0.04; -0.01 to 0.10; p=0.128), indicating that atherosclerosis may trigger neurodegeneration and lead to cognitive disorders, according to researchers.
“Possible mechanisms may be attributed to the role of atherosclerosis as a vascular disease that affects cognition through other vascular pathologies such as infarcts, and possibly exacerbates neurodegeneration through interaction with pathologies such as Alzheimer's disease,” they said.
Participants were recruited from the Epidemiology of Dementia in Singapore study. Only participants who tested positive in the abbreviated mental test and self-reported progressive forgetfulness surveys were included.
ABI was calculated using measured ankle and brachial blood pressures. CeVD markers were measured using MRI. A previously validated neuropsychological battery test was used to assess cognitive function of the participants.
“As the association between low ABI and cognitive function is influenced by [CeVD and neurodegenerative markers], greater emphasis should be placed on the treatment of risk factors and on delaying the progression of atherosclerotic disease,” researchers said.