Abstract
BackgroundNosocomial infections are extremely common in the elderly and may be related to ageing of the immune system. The Immune Risk Phenotype (IRP), which predicts shorter survival in elderly patients, has not been evaluated as a possible risk factor for nosocomial infection. Our aim was to assess the prevalence of nosocomial infections in elderly in-patients and to investigate potential relationships between nosocomial infections and the immunophenotype, including IRP parameters.ResultsWe included 252 consecutive in-patients aged 70 years or over (mean age, 85 ± 6.2 years), between 2006 and 2008. Among them, 97 experienced nosocomial infections, yielding a prevalence rate of 38.5% (95% confidence interval, 32.5-44.5). The main infection sites were the respiratory tract (21%) and urinary tract (17.1%) When we compared immunological parameters including cell counts determined by flow cytometry in the groups with and without nosocomial infections, we found that the group with nosocomial infections had significantly lower values for the CD4/CD8 ratio and naive CD8 and CD4 T-cell counts and higher counts of memory CD8 T-cells with a significant increase in CD28-negative CD8-T cells. Neither cytomegalovirus status (positive in 193/246 patients) nor presence of the IRP was associated with nosocomial infections. However, nosocomial pneumonia was significantly more common among IRP-positive patients than IRP-negative patients (17/60 versus 28/180; p = 0.036).ConclusionImmunological parameters that are easy to determine in everyday practice and known to be associated with immune system ageing and shorter survival in the elderly are also associated with an elevated risk of nosocomial pneumonia in the relatively short term.
Highlights
Nosocomial infections are extremely common in the elderly and may be related to ageing of the immune system
The National Nosocomial Infections Survey done in the US in 1986-1990 showed that 54% of all Nosocomial infections (NIs) occurred in people aged 65 or over [3]
To evaluate the immune system in our elderly patients, we looked at two sets of abnormalities associated with ageing: (i) classical immunology variables, which showed decreases in naive T-cell subsets and increases in memory/effector cells; (ii) and the Immune Risk Phenotype (IRP), a combination of immunological alterations identified as associated with shorter survival in free-living healthy Swedes over 85 years of age [15,16,17]
Summary
Nosocomial infections are extremely common in the elderly and may be related to ageing of the immune system. The Immune Risk Phenotype (IRP), which predicts shorter survival in elderly patients, has not been evaluated as a possible risk factor for nosocomial infection. Risk factors for NIs vary with the infection site, healthcare setting, and patient age. Peripheral CD28- CD8 T-cell counts are elevated in elderly individuals [8,9,10] The expansion of this T-cell subset is related to the clonal T-cell expansions often detected in elderly individuals and leads to competition for CD8 T-cell survival niches, thereby hampering the immune responses to infections, most notably those of viral origin [10]
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