Patients with Lewy body dementia (LBD) and likely Alzheimer disease-type (AD-type) copathology, based on cerebrospinal fluid (CSF) biomarkers and autopsy data, performed worse on the Boston Naming Test (BNT) than patients with LBD without AD, according to study results published in Neurology.

Previous research has sought to distinguish the 2 dementias with limited success. Study researchers sought to determine clinical heterogeneity to allow for improved prognosis and treatment.

They retrospectively selected 57 patients with LBD from the University of Pennsylvania Integrated Neurodegenerative Disease Database based on clinical diagnosis of LBD (dementia with Lewy bodies [DLB], n=38, or Parkinson disease dementia (PDD), n=19) and availability of CSF biomarkers or autopsy diagnosis and BNT data collected after dementia onset. PDD and DLB were distinguished using the 1-year interval between Parkinsonism motor symptoms and dementia onset and blinded from CSF data.


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The study researchers categorized patients as LBD with (LBD+AD, n=26) and without (LBD-AD, n=31) AD-type copathology based on autopsy-validated CSF cut-point or autopsy data.

They assessed confrontation naming, which relies on the temporal lobe, with the BNT and the Multi-Lingual Naming Test of the groups divided based on AD-type copathology and according to PDD and DLB clinical diagnostic criteria.

The PDD group participants were older at times of dementia onset and test date, and the DLB group participants had a longer interval between dementia onset and test date (both P <.01). Clinical groups also differed in core clinical features: the PDD group had more Parkinsonism motor symptoms while the DLB group had more frequent hallucinations, cognitive fluctuations, and rapid eye movement (REM) sleep behavior disorder (RSBD; all P <.05). LBD+AD patients performed worse than LBD-AD patients on confrontation naming (BNT, F=4.8; P =.03).

In covariate analysis, education was significantly associated with BNT performance between biologically defined groups (F=7.62; P =.008). BNT and education were positively correlated (rho=0.36; P =.007). BNT and CSF t-tau (rho=-0.28; P =.04) and p-tau (rho=-0.26; P =.05) were inversely correlated.

Excluding the 3 patients with CSF collection prior to dementia onset, BNT performance was still significantly different between LBD+AD and LBD-AD groups (F=5.50; P =.02), but not between clinical phenotypes (P =.04). BNT and p-tau correlation remained (rho=-0.29; P =.03). Omitting high leverage points, BNT was significantly associated with t-tau (rho=-0.31; P =.03) and p-tau (rho=-0.39; P =.005) but not Aβ42.

Limitations of the study included the retrospective nature of neuropsychological data and limited testing in specific cognitive domains, such as episodic memory recall and visuo-construction, and that greater impairment in LBD+AD could be attributed to more general impairment from a more advanced stage of disease than LBD-AD.

The study researchers concluded that the evidence suggested “a selective, domain-specific cognitive impairment in language” in patients with LBD and AD-type copathology and that cognition in clinically defined LBD syndromes (DLB, PDD) “remains heterogeneous.” They added that stratifying cohorts of patients with LBD based on AD-type copathology may be advantageous for prognosis and treatment.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Howard E, Irwin DJ, Rascovsky K, et al. Cognitive profile and markers of Alzheimer disease-type pathology in patients with Lewy body dementias. Neurology. 96(14):e1855-e1864. doi:10.1212/WNL.0000000000011699