Total and phospho-tau (threonin 181) in geriatric major depression and mild cognitive impairment

In Alzheimer’s disease (AD) an accelerated neurofibrillary tangle formation leads to an increased tau protein release into the CSF. Significantly increased CSF total and phospho-tau levels were found in patients at risk to develop AD indicating its potential as a marker of AD.

85 patients with aging-associated cognitive decline (AACD), 57 patients with geriatric major depression and 33 controls were included. In all participants, CSF levels of total tau and tau protein phosphorylated at threonine 181 (p-tau) were determined by ELISA at baseline. Patients were reinvestigated during follow-up, and total and p-tau baseline levels were compared between the diagnostic groups. CSF total tau and p-tau levels distinguished significantly geriatric major depression from AACD. During follow-up, 28% of the AACD patients converted to AD. Already at baseline, converters showed significantly higher both total tau and p-tau levels than the non-converters.

In conclusion, our findings reflect and confirm the clinical judgement of an incipient neurodegenerative disorder in a considerable portion of AACD patients. CSF total and p-tau levels distinguish major geriatric depression from AACD and by this may facilitate early diagnosis of AD.