Reports from older adults and their partners of early memory issues are associated with higher levels of tau neurofibrillary tangles in the brain, new research suggests.
The findings show that in addition to beta-amyloid, tau is implicated in cognitive decline even in the absence of overt clinical symptoms.
“Understanding the earliest signs of Alzheimer’s disease is even more important now that new disease-modifying drugs are becoming available,” study author
Rebecca E. Amariglio, PhD, clinical neuropsychologist at Brigham and Women’s Hospital and the Massachusetts General Hospital and assistant professor in neurology at Harvard Medical School, Boston, said in a news release. “Our study found early suspicions of memory problems by both participants and the people who knew them well were linked to higher levels of tau tangles in the brain.”
The study was published online in Neurology.
Subjective Cognitive Decline
Beta-amyloid plaque accumulations and tau neurofibrillary tangles both underlie the clinical continuum of Alzheimer’s disease (AD). Previous studies have investigated beta-amyloid burden and self- and partner-reported cognitive decline, but fewer have examined regional tau.
Subjective cognitive decline may be an early sign of AD, but self-awareness declines as individuals become increasingly symptomatic. So, a report from a partner about the participant’s level of cognitive functioning is often required in studies of mild cognitive impairment and dementia. The relevance of this model during the preclinical stage is less clear.
For the multicohort, cross-sectional study, investigators studied 675 cognitively unimpaired older adults (mean age, 72 years; 59% female), including persons with nonelevated beta-amyloid levels and those with elevated beta-amyloid levels, as determined by PET.
Participants brought a spouse, adult child, or other study partner with them to answer questions about the participant’s cognitive abilities and their ability to complete daily tasks. About 65% of participants lived with their partners and both completed the Cognitive Function Index (CFI) to assess cognitive decline, with higher scores indicating greater cognitive decline.
Covariates included age, sex, education, and cohort as well as objective cognitive performance.
The Value of Partner Reporting
Investigators found that higher tau levels were associated with greater self- and partner-reported cognitive decline (P < .001 for both).
Significant associations between self- and partner-reported CFI measures were driven by elevated beta-amyloid levels, with continuous beta-amyloid levels showing an independent effect on CFI in addition to tau.
“Our findings suggest that asking older people who have elevated Alzheimer’s disease biomarkers about subjective cognitive decline may be valuable for early detection,” Dr. Amariglio said.
Limitations include the fact that most participants were White and highly educated. Future studies should include participants from more diverse racial and ethnic groups and people with diverse levels of education, researchers noted.
“Although this study was cross-sectional, findings suggest that among older CU individuals who at risk for AD dementia, capturing self-report and study partner report of cognitive function may be valuable for understanding the relationship between early pathophysiologic progression and the emergence of functional impairment,” the authors concluded.
The study was funded in part by the National Institute on Aging, Eli Lily, and the Alzheimer’s Association, among others. Dr. Amariglio receives research funding from the National Institute on Aging. Complete study funding and other authors’ disclosures are listed in the original paper.
A version of this article first appeared on Medscape.com.