Cerebrospinal fluid biomarkers in older adults with mild cognitive impairment, with and without a major depressive disorder

Abstract Background Mild Cognitive Impairment (MCI) and Major Depressive Disorder (MDD) have been independently associated with increased risk of dementia. Cerebrospinal fluid (CSF) biomarkers associated with Alzheimer’s disease (AD) show changes prior to the onset of symptoms of dementia or neuroimaging biomarkers of AD. We examined the association between a CSF biomarker profile of AD and diagnosis in three groups: MCI alone; a diagnosis of MDD alone; or MCI plus a diagnosis of MDD. Method The CSF total tau, p‐tau, amyloid‐β 42 , and the p‐tau/ amyloid‐β 42 ratio were measured in 31 participants enrolled in the PACt‐MD study diagnosed with MCI (N=13), MDD (N=7), or both (MCI+MDD) (N=11) according to NIA‐AA and DSM IV criteria. We compared AD biomarkers in the 3 groups and then compared cognitive performance in those with and without a CSF biomarker profile consistent with AD Result Among the 31 participants, 9 had a CSF biomarker profile consistent with AD: 7/13 with MCI; 0/7 with MDD; and 2/11 with MCI+MDD. Participants with an AD biomarker profile had significantly greater impairment in verbal memory than those without one (p=0.009). Of those without a profile consistent with AD, no significant differences were observed in cognitive performance between the MCI and MDD+MCI groups. Conclusion In our sample, few participants with MDD had a CSF biomarker profile consistent with AD, even if they had a neurocognitive profile consistent with MCI. The etiopathology of cognitive impairment in older patients with MDD requires further investigation.