Alzheimer's hits harder earlier in life as people in their 60s decline more quickly than older patients
May be that patients diagnosed after 80 have some kind of 'resistance' to condition
12:12 GMT, 3 August 2012
People who develop Alzheimer's symptoms in their 60s and 70s, are more likely to decline quickly compared to those diagnosed in very old age, researchers say.
A team from the University of California said the 'younger elderly' showed faster rates of brain tissue loss and cognitive decline than Alzheimer patients who were over 80 years old.
The findings have profound implications for both diagnosing the degenerative condition and efforts to find new treatments. There is currently no cure for Alzheimer's and therapies can only ease some of the symptoms.
Early-onset: Author Terry Pratchett revealed when he was 59 that he had been diagnosed with Alzheimer's Disease. However, he has a very rare atypical form
Study author Dr Dominic Holland, said: 'One of the key features for the clinical determination of AD is its relentless progressive course.
'Patients typically show marked deterioration year after year. If older patients are not showing the same deterioration from one year to the next, doctors may be hesitant to diagnose AD, and thus these patients may not receive appropriate care, which can be very important for their quality of life.'
The team used imaging and biomarker data from 723 who participated in the Alzheimer's Disease Neuroimaging Initiative. The people aged 65 to 90 years, were categorised as either cognitively normal, with mild cognitive impairment or suffering from full-blown AD.
The degenerative condition is the most common form of dementia and affects more than 300,000 people in the UK.
It is estimated that it affects on in 14 people over the age of 65. It can be inherited in some cases.
Author Terry Pratchett is a high profile person with the disease.
The condition is caused by parts of the brain wasting away, particularly in the cerebral cortex.
As the grey matter wastes away, clumps of protein, known as ‘plaques’ and ‘tangles’, start to form in the brain. The plaques and tangles start to destroy even more brain cells.
Early symptoms include minor memory problems and saying the right words.
Later symptoms include severe confusion and dramatic changes of personality. A sufferer can also experience delusions.
There is no cure though there are some treatment that can slow the disease's progression.
The disease can shorten life-expectancy as sufferers can lose interest in eating and maintaining personal hygiene, leading to other illnesses.
Dr Holland said: 'We found that younger elderly show higher rates of cognitive decline and faster rates of tissue loss in brain regions that are vulnerable during the early stages of AD.
'Additionally cerebrospinal fluid biomarker levels indicate a greater disease burden in younger than in older individuals.'
Co-author Dr Linda McEvoy said it's not clear why AD is more aggressive among younger elderly.
'It may be that patients who show onset of dementia at an older age, and are declining slowly, have been declining at that rate for a long time.
'But because of cognitive reserve or other still-unknown factors that provide 'resistance' against brain damage, clinical symptoms do not manifest till later age.'
Another possibility, according to Dr Holland, is that older patients may be suffering from mixed dementia – a combination of AD pathology and other neurological conditions.
These patients might withstand the effects of AD until other adverse factors, such as brain lesions caused by cerebrovascular disease, take hold. However, as AD can only be diagnosed definitively by an autopsy this remains a theory.
'So we do not yet know the underlying neuropathology of participants in this study,' Holland said.
Dr Simon Ridley, Head of Research at Alzheimer’s Research UK, said:
'These findings challenge the misconception that Alzheimer’s and dementia is only a problem for much older people, suggesting it may be more aggressive in people in their 60s and 70s.
'The results highlight the importance of helping younger people with Alzheimer’s to access clinical trials, as new drugs could have a big impact on their lives.
'With more people reaching retirement age, it is important to understand how Alzheimer’s affects people of different ages.
'Understanding why very elderly people with Alzheimer’s are less likely to feel its full force could provide new clues for preventing or slowing the disease. To answer these questions, we must invest in research.'
The study is published online on 2 August in the journal PLoS ONE.