CMV infection, CD19+ B cell depletion, and Lymphopenia as predictors for unexpected admission in the institutionalized elderly

Background Chronic infections played a detrimental role on health outcomes in the aged population, and had complex associations with lymphocyte subsets distribution. Our study aimed to explore the predictive roles of chronic infections, lymphopenia, and lymphocyte subsets on unexpected admission and mortality in the institutionalized oldest-old during 3 year follow-up period. Results There were 163 participants enrolled prospectively with median age of 87.3 years (IQR: 83.1-90.2), male of 88.3%, and being followed for 156.4 weeks (IQR: 136.9-156.4 weeks). The unexpected admission and mortality rates were 55.2 and 24.5% respectively. The Cox proportional hazards models demonstrated the 3rd quartile of cytomegalovirus IgG (OR: 3.26, 95% CI: 1.55-6.84), lymphopenia (OR: 2.85, 95% CI: 1.2-6.74), and 1st quartile of CD19(+) B cell count (OR: 2.84, 95% CI: 1.29-6.25) predicted elevated risks of unexpected admission after adjusting for potential confounders; while the 3rd quartile of CD3(+) T cell indicated a reduced risk of mortality (OR: 0.19, 95% CI: 0.05-0.71). Negative association between CMV IgG and CD19(+) B cell count suggested that CMV infection might lead to B cell depletion via decreasing memory B cells repertoire. Conclusions CMV infection, lymphopenia, and CD19(+) B cell depletion might predict greater risk of unexpected admission, while more CD3(+) T cell would suggest a reduced risk of mortality among the oldest-old population. A non-linear or U-shaped relationship was supposed between health outcomes and CMV infection, CD3(+) T cell, or CD19(+) B cell counts. Further prospective studies with more participants included would be needed to elucidate above findings.