Tau deposition doesn’t predict cognitive status of Parkinson’s patients

The more tau accumulation in the brain, the greater the likelihood that neuroimaging will reveal similarly elevated levels of brain beta amyloid. However, the buildup of these proteins does not affect the cognitive status of patients with Parkinson’s disease, according to a PET-based study published online Dec. 11 in JAMA Neurology.

Senior author William Jagust, MD, of the University of California, Berkeley and colleagues examined the depositions of beta amyloid and tau in PET scans of 15 cognitively normal Parkinson’s patients and 14 with mild cognitive impairment, along with 49 healthy volunteers.

They found that depositions of tau and beta amyloid did not differ between the Parkinson’s patients who had mild cognitive impairment and their cognitively normal Parkinson’s peers.

They also found that the binding of the tau PET tracer 18F-AV-1451 in all the Parkinson’s patients was no different from that in the healthy controls who were negative for beta amyloid.

Further, beta-amyloid status in Parkinson’s patients was not related to cognitive status, and the proportion of patients with the disease who were beta amyloid-positive (21 percent) was comparable to that in healthy controls of similar age.

“To our knowledge, this is the first study to use PET scans to examine beta amyloid and tau in relationship to cognitive status in patients with Parkinson’s disease but not dementia, and the first finding that tau binding observed via PET scan is related to beta-amyloid status in patients with Parkinson’s disease without dementia,” the authors write in their discussion.

The JAMA Network has posted the PET study in full for free.

Also published online Dec. 11 in JAMA Neurology is a password-protected study showing that rigorous regular exercise can slow the progression of Parkinson’s disease. Northwestern University’s news office has posted a summary.