Peripheral lymphocyte counts and regional cerebral blood flow on brain SPECT correlate in Alzheimer's disease: A retrospective cross-sectional study.

BACKGROUND

Given emerging evidence of immune involvement in Alzheimer's disease (AD), we aimed to clarify whether peripheral lymphocyte counts are associated with regional cerebral blood flow (rCBF) as measured by brain single-photon emission computed tomography (SPECT). Identifying such a relationship may help to establish early, accessible biomarkers of disease progression.

METHODS

Participants were 111 patients diagnosed with AD at the Yokohama City University Hospital Medical Center for Dementia Diseases between January 2021 and December 2023 and who underwent blood tests and brain SPECT. Sex, age, cognitive function tests, peripheral blood values, and rCBF on brain SPECT were investigated retrospectively. Neutrophil and lymphocyte counts were extracted from blood values. In addition, the rCBF in each region (frontal, parietal, temporal, occipital, and limbic system) was calculated from brain SPECT, and correlation analysis between lymphocytes and rCBF was performed.

RESULTS

Significant positive correlations between lymphocyte counts in peripheral blood and rCBF were found in all regions except the left frontal lobe. In particular, the correlation coefficient between rCBF and lymphocyte count was highest in the right temporal lobe (ρ = 0.311, P = 0.001).

CONCLUSIONS

Peripheral blood lymphocyte counts are positively related to rCBF on brain SPECT, and lymphocytes can be an early biomarker that can be tested inexpensively and easily. Limitations include the retrospective cross-sectional design and single-center setting, which preclude analysis of causality and changes over time.