[JM 2]Hypertension and dementia: is there a link?

The age at which one acquires hypertension may matter on the risk of dementia later on, with mid-life hypertension shown to be associated with late-life dementia.

Although the association between hypertension in later-life and cognitive impairment is not consistent, hypertension contributes to both early cerebrovascular brain damage and cognitive
decline, according to Dr. Mohammad Kamran Ikram from Memory, Aging & Cognition Center at the National University of Singapore.

 “Dementia is a multi-factorial disease. It is a clinical syndrome whose main features are a progressive, global deterioration in cognitive function in which memory is especially affected. An important distinction from delirium is that there is a clear state of consciousness in patients and one of the decisive features is that it interferes with social and occupational function of a certain person,” Ikram said.

Diagnosing dementia is a two-step process: the clear identification of dementia syndrome followed by the search for etiology or specific disease syndrome. Ikram distinguished between dementia and the physiologic decline in memory and rate of information processing as people age – which does not affect daily function and significantly worsen.

Alzheimer’s disease is the most common cause of dementia, followed by vascular disease. In Alzheimer’s disease, a patient may experience amnesia, aphasia, apraxia, agnosia, behavioral and psychiatric symptoms such as psychotic features, personality change and activity disturbance. The prevalence and incidence of dementia increase exponentially with increasing age.

The risk factors for dementia include nutrition, cognitive reserve, genetics and cardiovascular disease. “A host of factors is involved in dementia. So, basically it is not a disease with one component. It is a disease with multiple component causes and what makes it worse is that there is a lot of fuzziness in these risk factors which give you the dementia syndrome,” Ikram explained.

Several big studies on hypertension and dementia have been conducted. The Goteburg study showed that blood pressure (BP) at age 70 years is related to onset of dementia at 79 to 85 years. The Honolulu-Asia Aging study showed that mid-life blood pressure is linked to late-life cognitive impairment. Among different BP components, systolic BP appears to be the strongest predictor of cognitive decline.

The pathologies that underlie the mechanisms for the link between hypertension and cognition include white matter changes, lacunar infarcts, microinfarcts, microbleeds and macrobleeds. Amyloid-β peptide accumulation and synaptic toxicity are neurodegenerative changes also related to hypertension.

The association of hypertension with dementia has led scientists to explore the impact of antihypertensive treatment on dementia later on. However, meta-analysis has not clearly shown the  positive impact of treatment on outcomes.