Cognitive impairment during acute illness in older patients is acknowledged, although factors that underpin this condition are less well studied.

To investigated the relationship between cognitive recovery and a range of clinical and biological variables.

Observational and longitudinal study. Participants were consecutive patients aged ≥70 years assessed within 3 days of their admission to elderly medical unit and re-assessed twice weekly with the DRS, CAM, MMSE, APACHE II, APS, Barthel index, frailty scale. Cytokines and APOE genotype were measured in a subsample.

142 patients were analysed [mean age 84.8±6.4; 47 (33%) male; 64, (45% with comorbid dementia]. 55 (39%) experienced cognitive improvement, of which 30 (54.5%) had delirium while 25 had non-delirious acute cognitive disorder. Using bivariate statistics, subjects with more severe acute illness, lower IGF-I levels and more severe delirium were more likely to experience ≥ 20% improvement in MMSE scores. When the criterion of cognitive improvement was a 3 point improvement in MMSE, those with more severe delirium, females and greater age were more likely to improve. Longitudinal analysis using any criterion of improvement indicated that improvement was significantly (p<0.05) predicted by higher levels of IGF-I, lower levels of IL-1 (alpha and beta), lack of APOE epsilon 4 allele, female gender and the interactions of APOE genotype with IGF-I, and dementia with IGF-I.

Cognitive recovery during admission is not exclusively linked to delirium status, but reflects a range of factors. The character and relevance of non-delirious acute cognitive disorder warrants further study