BEIJING, Oct. 13 (Xinhuanet) -- The visuospatial skills might decline years before an Alzheimer's patient is diagnosed, a new study in U.S. suggests as quoted by media reports Tuesday.

    Scientists in the U.S. picked up 444 people to make longitudinal studies. All participants were dementia-free when they were enrolled in the study and underwent tests on a number of cognitive abilities, including visuopatial skills.

    After an average follow-up of 5.9 years, 134 participants had developed dementia. Of those, 44 underwent brain autopsies that confirmed they had Alzheimer's disease.

    The researchers tried to used data from the cognitive assessments to chart declines in various areas before participants were diagnosed with dementia, and found a inflection point in visuospatial abilities three years before clinical diagnosis of dementia.

    Researchers also discovered that declines in overall cognition occurred the next year after participants's visuospatial abilities dropped, while inflection points for verbal and working memory weren't seen until one year before diagnosis.

    "There are several implications of this study," wrote David K. Johnson, of the University of Kansas, and colleagues.

    "Some of the earliest signs of preclinical disease may occur on tests of visuospatial and speeded psychomotor skills. Furthermore, the greatest rate of preclinical decline may occur on executive and attention tasks. These findings suggest that research into early detection of cognitive disorders using only episodic memory tasks, such as word lists or paragraph recall, may not be sensitive to either all of the earliest manifestations of disease or the most rapidly changing domain."

    "In summary, converging longitudinal evidence suggests that after a sharp departure from the relatively flat course of normal aging, there is a preclinical period in Alzheimer's disease with insufficient cognitive decline to warrant clinical diagnosis using conventional criteria but that can be seen with longitudinal data from multiple domains of cognition and not just memory," they added. 

    (Source: Agencies)