Immune risk phenotype and long-term mortality after community-acquired pneumonia in older adults: clinical and immune determinants.

BACKGROUND

Community-acquired pneumonia (CAP) has been associated with poor long-term outcomes in older adults. In most pre-pandemic studies, long-term mortality was assessed with a focus on comorbidity burden. Although immunosenescence is a key determinant of CAP, post-acute immune patterns have been little explored.

OBJECTIVE

To assess 18-month mortality after CAP hospitalisation and the prognostic value of the Immune Risk Phenotype (IRP).

METHODS

Prospective, observational study of adults ≥ age 65 years discharged after CAP (2019-21). We performed comprehensive geriatric and nutritional assessments, including laboratory tests at 30-60 days post diagnosis. IRP was defined as cytomegalovirus seropositivity with inverted CD4:CD8 ratio, elevated CD8 + T cell count, or expansion of CD8CD28-T cells. The main outcome measure was 18-month mortality. Multivariate logistic with ROC curves and Cox regression analyses were performed. (ClinicalTrials.gov, NCT0462799).

RESULTS

The sample included 143 patients (55.2% males), with a mean age of 77.6 ± 7.9 years. IRP was found in 46.8% of patients. Elevated lymphocyte count and female sex were predictors of IRP. At 18 months post-CAP, 27 patients (18%) had died, mainly due to infections (n = 13, 48%) and fractures (n = 2, 7.4%). Predictors of 18-month mortality included IRP (HR 2.58 [95% CI 1.11-5.99]; p = 0.027), severe chronic kidney disease (6.16 [2.53-14.99]; p<0.001), poor functional status (3.69 [1.53-8.90] p = 0.004), and hypoalbuminemia (3.35; [1.34-8.41]; p = 0.010).

CONCLUSIONS

This study underscores the role of infectious complications in long-term outcomes after CAP. These findings highlight the need for comprehensive geriatric assessment to identify multidimensional risk factors, including immunosenescence as a potentially modifiable domain warranting further investigation and integration into care.