No evidence of delay in dementia progression

SINGAPORE - Tuesday's article ("Don's study sheds light on dementia here") raised the controversial statement that "early treatment - including proper nutrition, stimulatory activities such as exercise or listening to music, and medication - has been shown to effectively delay the progression of dementia".

Dementia is a syndrome of cognitive impairment with diverse causes.

Three diseases make up the bulk of dementia cases in Singapore: Alzheimer's disease, vascular dementia (when one or more strokes damage critical brain functions) and mixed dementia (a combination of stroke and Alzheimer's disease).

The rate of disease progression varies greatly even within each category.

Everybody hopes that treatment can delay disease progression in dementia.

Unfortunately, apart from blood pressure control and anti-stroke medications for vascular dementia, there is no evidence that we can delay dementia progression.

Many researchers have admitted failure in modifying disease progression in Alzheimer's.

Drugs may improve short-term memory, alleviate symptoms, make patients more manageable and even help to delay institutionalisation, but they do not change the natural history of the disease.

Researchers planning well-funded prospective studies of drug and non-drug interventions in dementia are confounded by two major problems.

First, dementia, including Alzheimer's disease, is a clinical diagnosis. The milder the dementia, that is, the earlier one makes the diagnosis, the less certain one is of the aetiological diagnosis.

Second, any assessment of social intervention or drug efficacy is confounded by variables like age, educational background, social class, medical co-morbidities and so on.

Professor Kua Ee Heok's retrospective study, based on a clinical diagnosis of dementia made over the last 15 to 20 years - in some cases, before high-quality neuroimaging was available - will face insurmountable challenges.

Misdiagnosis or misclassification (which is a common problem even in the best of hands) could easily corrupt data.

The condition of a patient with vascular dementia arising from a few small strokes could remain static for many years before a second stroke in a critical location, or even new-onset Alzheimer's disease, pushes him overboard. It would be easy to misinterpret this delay in progression and give credit to social intervention or medications.

Thus, we cannot see the scientific basis behind the claim that "with proper treatment, a patient with a mild form of the condition (dementia)... can delay the onset of the next stage to six or eight years later".

Tang Kok Foo (Dr)

Tan Chue Tin (Dr)

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