Increasing cognitive decline for cognitively healthy results in convergence of several measures
FRIDAY, Aug. 3 (HealthDay News) -- The rates of cognitive decline and atrophy characteristic of Alzheimer's disease (AD) decrease with advancing age, while cognitively healthy individuals show increased rates, according to a study published online Aug. 2 in PLoS One.
Dominic Holland, Ph.D., of the University of California in San Diego, and colleagues evaluated the rate of change in cognitive function and atrophy in specific regions of the brain measured using magnetic resonance imaging. Participants included 723 adults aged 65 to 90 years with AD or mild cognitive impairment (MCI), or who were cognitively healthy.
The researchers found that, as people aged, the rate of cognitive decline and atrophy slowed down substantially for those with AD and MCI but increased for those who were cognitively healthy at baseline. For several measures there was a convergence in the rates of change for patients and cognitively healthy controls with advancing age. The cerebrospinal fluid density of several AD-related proteins, particularly phospho-tau181p, converged with advancing age
"These results imply that the phenotypic expression of AD is relatively mild in individuals older than approximately 85 years, and this may affect the ability to distinguish AD from normal aging in the very old," the authors write. "Our findings show that inclusion of older individuals in clinical trials will substantially reduce the power to detect disease-modifying therapeutic effects, leading to dramatic increases in required clinical trial sample sizes with age of study sample."
Several authors disclosed financial ties to CorTech Labs Inc. Data collection was funded by the Alzheimer's Disease Neuroimaging Initiative, which is funded by the pharmaceutical industry.