• Melanie Dani, Lucy H Owen, Thomas A Jackson, Kenneth Rockwood, Elizabeth L Sampson, and Daniel Davis.
• Department of Medicine for the Elderly, Hammersmith Hospital, London, UK.
• J. Gerontol. A Biol. Sci. Med. Sci. 2018 Mar 2; 73 (3): 415-418.

BackgroundIt is unknown whether the association between delirium and mortality is consistent for individuals across the whole range of health states. A bimodal relationship has been proposed, where delirium is particularly adverse for those with underlying frailty, but may have a smaller effect (perhaps even protective) if it is an early indicator of acute illness in fitter people. We investigated the impact of delirium on mortality in a cohort simultaneously evaluated for frailty.MethodsWe undertook an exploratory analysis of a cohort of consecutive acute medical admissions aged ≥70. Delirium on admission was ascertained by psychiatrists. A frailty index (FI) was derived according to a standard approach. Deaths were notified from linked national mortality statistics. Cox regression was used to estimate associations between delirium, frailty, and their interactions on mortality.ResultsThe sample consisted of 710 individuals. Both delirium and frailty were independently associated with increased mortality rates (delirium: HR 2.4, 95% CI 1.8-3.3, p < .01; frailty (per SD): HR 3.5, 95% CI 1.2-9.9, p = .02). Estimating the effect of delirium in tertiles of FI, mortality was greatest in the lowest tertile: tertile 1 HR 3.4 (95% CI 2.1-5.6); tertile 2 HR 2.7 (95% CI 1.5-4.6); tertile 3 HR 1.9 (95% CI 1.2-3.0).ConclusionAlthough delirium and frailty contribute to mortality, the overall impact of delirium on admission appears to be greater at lower levels of frailty. In contrast to the hypothesis that there is a bimodal distribution for mortality, delirium appears to be particularly adverse when precipitated in fitter individuals.© The Author 2017. Published by Oxford University Press on behalf of The Gerontological Society of America.

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