CD38 and Mental deterioration: Within the B cell compartment, IgD− CD27− B cells (as a percentage of B cells) demonstrated potential cognitive protective effects (β = 0.03, 95% CI: 0.01 to 0.04, p = 1.10 × 10−3), whereas CD27 expression on memory B cells (β = −0.02, 95% CI: −0.03 to −0.01, p = 1.26 × 10−3) and CD38 expression on transitional B cells (β = −0.02, 95% CI: −0.03 to −0.01, p = 3.96 × 10−3) were associated with potential cognitive decline.