Looking out for signs of early onset dementia

Dementia is a terrible disease no matter what age it strikes, but did you know that it can even affect people in their 40s and 50s? Acclaimed neurologist Professor Peter Garrard is here to explain early onset dementia.

Young onset dementia is loosely defined as cases occurring in people under 65, or at working age. In this age group, the prevalence of dementia is very low, affecting less than 1% of the population. As people age, the incidence increases by about 5% per year; after 90 between a quarter and a third of people will have dementia. It is a disease of ageing – that is to say, ageing is one of the major risk factors.

Signs and symptoms of dementia

In younger patients, the probability of having dementia is very low. Consequently, it is often not suspected and can go undiagnosed for longer. Older people are known to be at increased risk, so dementia is suspected earlier and diagnosed more quickly.

Dementia can be diagnosed when the patient exhibits symptoms of cognitive failure, including the following:

• Memory impairment
• Language loss
• Behavioural change
• Inability to navigate or use visual apparatus to perform daily tasks

It is important to realise that dementia doesn’t always present with memory problems or forgetfulness. It can also present with visual/navigation problems – this can include difficulty with reading, driving, or navigating around the house. This is often dismissed as indicating visual impairment and the patient is referred on to an optician or ophthalmologist. In reality it is a symptom of visual processing impairment, which is caused by damage within the brain, and must therefore always be taken seriously.

There are also language symptoms: changes in word-finding ability and in understanding more complex words.

Behavioural symptoms are also indicative of dementia. Personalities can change and patients begin to exhibit bizarre behaviours, making normal lives with social and work environments difficult.

Mechanisms of dementia

There are several possible underlying causes and pathologies for dementia that we look for:

• Alzheimer’s disease – the most common cause overall. However, in the younger onset population, those patients with Alzheimer’s account for maybe one third. Alzheimer’s involves the accumulation of proteins, chiefly amyloid and tau, in the brain.
• Premature vascular dementia – a large proportion of early-onset cases are caused by this.
• Non-Alzheimer neurodegenerative conditions – there are two sub-types: tauopathies (in which clumps of the ‘nerve cell scaffolding’ protein tau accumulates, without amyloid, in the brain); and those involving a build-up of a different protein, called TDP43.

While Alzheimer’s tends to affect the posterior regions of the brain, impacting on visual processing and memory, non-Alzheimer neurodegenerative conditions tend to affect frontal areas, causing problems with language and behaviour.

The mechanisms in all these underlying pathologies are unknown, but a proportion (about 5-10% of cases) will be due to inheriting a faulty gene. Such people usually have a family history of dementia. However, the majority of cases are not inherited, and the cause or causes are unknown. The mechanisms leading to sporadic dementia are the focus of intensive research around the world.

Professor Garrard: how to recognise Alzheimer’s disease

Can you prevent dementia?

Risk factors include:

• Hypertension
• Smoking
• Excessive alcohol consumption
• Obesity
• Diabetes
• Lack of exercise

These lower resistance to neurodegenerative disease as you age. However, even by avoiding all of the above, it is impossible to eliminate the incidence of dementia completely.

Homocysteine is a potent risk factor. There is evidence that if you lower homocysteine in Alzheimer’s patients with above-average levels, you can stabilise their cognition, but there needs to be a large clinical trial to prove its benefits.

For more information on dementia or to book an appointment with Professor Garrard, visit his Top Doctors profile.