Association of Intracranial Atherosclerotic Disease With Incident Dementia

Intracranial atherosclerotic disease and dementia

Often, when we think of dementia, we think of Alzheimer's dementia with all the amyloid plaques and tangles that cause neurons to die off. However, anything that causes neurons to die can lead to dementia. And here we often think of stroke and how it destroys brain tissue, leading to disability and dementia.

Usually, we think of the extracranial vessels. We think of carotid stenosis and clot formation from carotid plaque causing strokes. However, what about the vessels that are inside the cranium? If there is ongoing atherosclerosis within these vessels, the blood flow would be compromised, which could lead to damaged neurons. This is referred to as intracranial atherosclerotic disease (ICAD). This disease differs from small vessel disease, called cerebral small vessel disease (CSVD). CSVD causes those white matter lesions that we see on MRI scans.

For this study, the researchers wanted to know whether narrowing of the intracranial arteries would increase dementia risk. This would be the segment of arteries between the large external arteries and the small cerebral vessels.

The ARIC Study (Atherosclerosis Risk in Communities) had MRI scans of 1590 people who did not have dementia. The authors noticed that 34.6% of the patients had ICAD as seen on the MRI scans. After 5.6 years of follow-up, 286 patients developed dementia.

When the authors examined patients with ICAD with greater than 50% stenosis, the risk of dementia was 94% higher (HR, 1.94; 95% CI, 1.32–2.84) compared with those without ICAD. For patients with any level of ICAD compared with those with no ICAD, the risk of dementia was 57% higher (1.57; 95% CI, 1.17–2.11). These results were after adjusting for cardiovascular risk factors, APOE4, and CSVD. This means that atherosclerosis in the intracranial vessels independently drives dementia risk.

This makes sense because if blood flow to neurons is not enough, these neurons cannot maintain homeostasis. Hence, they become damaged and may eventually die. Therefore, to prevent dementia, we need to keep the blood vessels happy.

So, whatever is good for the heart is also good for the brain. Having optimum blood pressure, cholesterol, and sugar levels, avoiding smoking, and reducing inflammation in blood vessels all reduce vascular damage. Even vaccinations that prevent infections like influenza, RSV infection, and COVID-19, could reduce inflammation and protect the vasculature. In addition, we should avoid PM_2.5 pollution particles and microplastics, which have been linked to vascular damage.

So, let us be good to our hearts and brains, and hopefully, we can “forget” about dementia.