Three key questions answered:
Dr Crispin Fisher and
Mr Andrew Larner answer three questions about this condition, which commonly presents in primary care
1. How can we distinguish between Alzheimer's disease and cerebrovascular disease?
It is taught that Alzheimer's disease presents with a slow, insidious decline, whereas vascular dementia presents in a step-like manner, with acute deteriorations followed by plateau phases of stability. Regrettably, it is not so simple. Vascular dementia is a heterogeneous disorder, which may present with progressive cognitive decline.
Increasingly, an overlap between Alzheimer's and cerebrovascular disease has been recognised. Mid-life hypertension and hypercholesterolaemia, traditional vascular risk factors, are now known to predispose to late-life Alzheimer's disease, and concurrence of vascular and Alzheimer's pathology is common in community-based populations of dementia patients at post-mortem.
There is evidence that treatment of hypertension may reduce the risk of dementia, including Alzheimer's disease.
A study has reported that most patients with a diagnosis of vascular dementia turned out to have either Alzheimer's disease alone or mixed disease at post-mortem.
Although various sets of criteria exist for the definition of vascular dementia, these are not easily applied in primary care; some for example, require brain imaging.
The Hachinski ischaemic score (see left) may be useful to differentiate Alzheimer's and vascular dementia, but some degree of misclassification is inevitable.
2. If I suspect dementia, should I refer to a psychiatrist, a geriatrician or a neurologist?
More neurologists are now interested in dementia, although they are still much thinner on the ground than old-age psychiatrists, elderly care physicians and geriatricians.
Some neurology-based memory or cognitive clinics restrict assessment to early-onset cases, meaning before age 65 an arbitrary distinction. If the issue is largely diagnostic, neurologists have better access to testing.
In elderly individuals with multiple co-morbidities a geriatrician may be most appropriate. If behavioural and psychological symptoms are prominent (depression, hallucinations, wandering) old-age psychiatrists may be best placed to help. Social and pastoral care is more easily organised by geriatricians and old age psychiatrists, rather than by ivory-tower-dwelling neurologists.
3. Should GPs prescribe statins for all patients with memory loss?
Statins are indicated in cerebrovascular
disease, and there is evidence that statin use reduces the risk of developing Alzheimer's disease, which correlates with the demonstration that hypercholesterolaemia may be a risk factor. However, it does not follow that statins should be prescribed in established Alzheimer's. Epidemiological studies have indicated potential protective value of NSAIDs and HRT but controlled clinical trials have shown the effects of these drugs to be consistently negative.
There is recent evidence, again observational, that lipid-lowering agents may slow disease progress, but pending the results of high-quality, randomised controlled trials statin therapy for established Alzheimer's cannot be recommended.
Crispin Fisher is a GP in Leominster, Herefordshire, and Andrew Larner is consultant neurologist, cognitive function clinic, Walton Centre for Neurology and Neurosurgery, Liverpool
Find the full version of this article in The Practitioner, free with your copy of Pulse next week