An immune risk phenotype, cognitive impairment, and survival in very late life:: Impact of allostatic load in Swedish octogenarian and nonagenarian humans

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.