Academic journal article Indian Journal of Psychiatry

Prevention of Dementia: Role of Vascular Risk Factors and Cerebral Emboli

Academic journal article Indian Journal of Psychiatry

Prevention of Dementia: Role of Vascular Risk Factors and Cerebral Emboli

Article excerpt

Byline: Nitin. Purandare

Dementia is a major health problem worldwide and the number of people affected is expected to rise considerably, especially in developing countries like India. Vascular risk factors are involved in causation of both vascular dementia and Alzheimer's disease (AD), account for 90% of all dementias. A selective review of the literature was conducted to summarize the current evidence from clinical studies to examine the role of vascular risk factors in prevention of dementia. Epidemiological evidence suggests that control of vascular risk factors may prevent, or at least delay, the onset of dementia. This finding is supported to some extent by randomized controlled trial evidence for treatment of hypertension but not for other risk factors. However, a number of methodological issues need addressing. There is a need for a randomized controlled trials (RCT) targeting multiple vascular risk factors in patients at increased risk of dementia; i.e., those with mild cognitive impairment. The research should also explore novel risk factors and mechanisms of vascular brain damage. For example, asymptomatic spontaneous cerebral emboli have been shown to be more frequent and associated with a more rapid progression of dementia in both AD and vascular dementia.

Introduction

Dementia affects over 24 million people worldwide.[sup] [1] In India, the prevalence of dementia in those over the age of 65 years is 1-3%[sup] [2] and the prevalence may be higher in urban compared to rural areas. The prevalence of dementia is expected to rise over next three to four decades with biggest increase in developing countries like India.[sup] [1] The precise economic and social burden of dementia in India remains unknown but there is some evidence to suggest higher economic cost and carer strain.[sup] [3] Dementia is a chronic progressive condition with no cure and delaying its onset could have a big impact on its prevalence. If the onset of dementia could be delayed by about five years then its prevalence could almost be halved.[sup] [4]

Alzheimer's disease (AD) and vascular dementia (VaD) account for about 90% of all dementias with evidence of considerable overlap between the two and "mixed" dementia is common.[sup] [2],[5] The Nun study showed the additive effect of cerebrovascular and neurodegenerative pathologies in producing clinical dementia. A fewer neuropathological lesions of AD were required for the clinical manifestation of dementia in those who had infarcts in basal ganglia, thalamus or deep white matter.[sup] [6] This selective review focuses on the potential role of vascular risk factors, specifically evidence from clinical studies, in the prevention of AD and VaD.

Vascular Risk Factors

Hypertension, hypercholesterolaemia, elevated homocysteine, diabetes, heart disease, smoking, and carotid artery disease are known risk factors for dementia, AD, and VaD.

Hypertension

A number of cross-sectional and epidemiological studies have shown than hypertension in midlife is a risk factor for dementia in old age. For example, Honolulu Asia Aging Study (HAAS) followed 3731 Japanese American men for over 14 years with autopsy data on 650 participants.[sup] [7] High systolic blood pressure (BP ≥160 mm of Hg) in midlife was associated with increased risk of dementia in old age. Hypertension was also associated with lower total brain weight, increased senileplaques (SP) count and hippocampal atrophy. A coexistence of SP and lacunar infarcts further increased the risk of incident dementia. Interestingly, the BP drops around the time of or soon after the onset of clinical dementia. The Kungsholmen project followed 947 people aged ≥75 years every three years for six years.[sup] [8] BP decreased significantly over three years prior to and following diagnosis of dementia. In people with baseline systolic BP< 160 mm of Hg, a drop of ≥15 mm of Hg over the first follow up was associated with an increased risk of dementia at the second follow up (relative risk, RR=3. …

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