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In the previous OCTO longitudinal study, we identified an immune risk phenotype (IRP) of high CD8 and low CD4 numbers and poor proliferative response. We also demonstrated that cognitive impairment constitutes a major predictor of nonsurvival. In the present NONA longitudinal study, we simultaneously examine in a model of allostatic load IRP and compromised cognition in 4-year survival in a population-based sample (n = 138, 86-94 years). Immune system measurements consisted of determinations of T-cell subsets, plasma interleukin 6 and cytomegalovirus and Epstein-Barr virus serology. Interleukin 2 responsiveness to concanavalin A, using data from the previous OCTO (octogenarians) immune study, hereafter OCTO immune, was also examined. Cognitive status was rated using a battery of neuropsychological tests. Logistic regression indicated that the IRP and cognitive impairment together predicted 58% of observed deaths. IRP was associated with late differentiated CD8+CD28-CD27- cells (p < .001), decreased interleukin 2 responsiveness (p < .05) and persistent viral infection (p < .01). Cognitive impairment was associated with increased plasma interleukin 6 (p < .001). IRP individuals with cognitive impairment were all deceased at the follow-up, indicating an allostatic overload.

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As a part of an ongoing longitudinal investigation, this study examined relationships between survival and selected immune system parameters in a sample (n = 102) of very old individuals (86-92 years at the time of initial immune system data collection). Analyses were performed comparing initial time-point measurements from those individuals who were alive (n = 75) and those who were deceased (n = 27) two years after initial data collection. Immune system measurements consisted of determination of peripheral blood lymphocytes and lymphocyte subsets, as well as T-cell responses to activation by Concanavalin A. Cluster analysis identified a subgroup associated with nonsurvival which indicated characteristics that included: poor T-cell proliferative responses, high CD8 percentages, and low CD4 and CD19 percentages. This multivariate analysis suggested that combinations of immune system parameters predict two-year survival otherwise not apparent when single immune system parameters were evaluated in the elderly.

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