Abstract

Dementia is a neurological disease that is associated with aging. The incidence and prevalence of dementia is increasing as the population continues to age. The two most common forms of dementia are Alzheimer's disease (AD) and vascular dementia (VaD). Although these two forms of dementia represent different pathologies and different clinical presentations, they share similar risk factors. It is important to distinguish between the two forms of dementia because of the differing treatments, and because the risk factors for each are often preventable. This article will discuss the classification, risk factors, and diagnosis of AD and VaD, and present distinguishing characteristics between them.

Introduction

Dementia is defined as a neurological syndrome consisting of impaired cognition that is severe enough to interfere with social or occupational functioning.^[1] In 2001 an estimated 364,000 older Canadians lived with dementia;^[2] by 2021, that number is projected to total 592,000.^[2] Some of the risk factors for dementia are advanced age, family history, educational level, and presence of vascular risk factors.

The two most common forms of dementia are Alzheimer's disease (AD) and vascular dementia (VaD).^[3] The prevalence of Alzheimer's disease is 4.4% whereas that of VaD is 1.4%.^[2] A clinician should consider a diagnosis of AD for an individual who presents with dementia that is characterized by a gradual and progressive course of short-term memory impairment without lateralizing signs, symptoms, or lateralized cognitive deficits.^[4] Alternately, a diagnosis of VaD would be appropriate for an individual who presents with an acute onset and stepwise progression of cognitive impairment.^[5]

While the foregoing distinction is useful, it should be noted that the differences between AD and VaD are not always obvious. A myriad of overlapping characteristics exist between them, including the cognitive decline often associated with aging. Impairments associated with normal aging are limited to rote memory and delayed recall. In contrast, patients with AD often manifest impaired abilities to form new memories whereas patients with VaD are cognitively impaired in executive functioning activities such as organizing, planning, and initiating sequential events. The pathological hallmarks of both dementias frequently coexist, as seen in postmortem analyses of older adults with dementia.^[6] Furthermore, there is considerable overlap between risk factors associated with AD and VaD. As with all dementias, organic reversible causes such as Vitamin B12 and folate deficiencies as well as thyroid abnormalities must be ruled out in order to make a definitive diagnosis.

Despite these difficulties it is important for clinicians to differentiate between patients with AD and VaD for several reasons. First, differentiating between these two types of dementia will enable researchers to accurately study their prevention, risk factors, and pathophysiology. Second, accurate diagnosing of AD and VaD is required to determine which form of treatment will most benefit the patient. This article will focus on the clinical diagnosis and risk factors associated with AD and VaD, and will examine the overlap between the two.

../..