Scientists look for patterns of Alzheimer early warning signs
An international team of researchers, led by Lars Bäckman from Sweden's Karolinska Institute, has examined ten years of clinical studies on Alzheimer's with the aim of creating a clear picture of the cognitive problems which will develop in people with the degenerative brain disease. The study, recently published in the journal Neuropsychology, reveals that people can show early warning signs across several cognitive domains ten years before they are officially diagnosed. The main reason for neuropsychologists' eagerness to unveil the preclinical stage of Alzheimer's is that understanding the transition from normal ageing to dementia is vital in understanding how the disease evolves. Moreover, if scientists succeed in identifying at-risk individuals early, treatment can be more effective. Researchers at the Karolinska Institute and Stockholm Gerontology Research Centre cooperated with the Max Planck Institute for Human Development and the University of South Florida to examine 47 peer-reviewed studies published between January 1985 and February 2003; 1985 marks the introduction of more systematic and reliable diagnostic criteria for Alzheimer's. The reports include records on 1,207 people with preclinical Alzheimer's, who later developed the disease, and 9,097 controls who stayed healthy. Their analysis showed that in all the studies, people at the preclinical stage exhibited marked preclinical deficits in global cognitive ability, episodic memory, perceptual speed, and executive functioning; along with somewhat smaller deficits in verbal ability, visuospatial skill, and attention. There was no preclinical impairment in primary memory. According to the authors, the generalised nature of the problem is consistent with recent observations that multiple brain structures and functions are affected long before the Alzheimer's diagnosis. They do point out however that the deficits seen in preclinical Alzheimer's mirrors quite closely those seen in normal ageing, such as impairments in episodic memory, executive functioning, and cognitive speed. Lead author Lars Backman says though, that these problems are exacerbated in those who will go on to be diagnosed with dementia. He says that as there are no clear qualitative differences in patterns of cognitive impairment, between the normal 75-year old, and the preclinical Alzheimer's counterpart, this presents an obvious challenge for accurate early diagnosis. The study also supports the emerging consensus that Alzheimer's preclinical period is characterised by an early onset followed by relative stability until a few years before diagnosis, when functioning plummets. A multi-variable approach to understanding the preclinical stage of Alzheimer's, which will help clinicians to predict more accurately the likelihood of disease, is encouraged by Backman and his colleagues. The research also revealed other interesting patterns: it was found that people younger than 75 years at baseline were more impaired at the outset than people older than 75 at baseline. Impairment was also greater for the patients with shorter periods (fewer than three years) to diagnosis. These findings suggest that preclinical impairment is greater when the disease starts younger, and progresses more quickly due to more widespread and severe brain lesions.
Countries
Germany, Sweden