Plasma insulin growth factor-1 and incident delirium in older people

Background A variety of demographic and clinical variables are acknowledged as risk factors for delirium; a syndrome thought to be mediated by abnormalities in a wide range of neurotransmitters. However, little research has been conducted in this field and the role of neuro-immunological factors as a mechanism of medication has received very little attention. Aims To determine if low baseline (on admission) IGF-1 levels (a protective cytokine released by brain cells in response to insult) is a risk factor for incident delirium in patients aged 75 and over admitted to an acute medical ward. Method Base line demographic and clinical variables and serum IGF-1 levels were measured in a consecutive series of 100 non-delirious subjects on inpatient admission. Subjects were assessed daily regarding the development of delirium during the inpatient episode. Results Twelve patients developed incident delirium. IGF-1 (OR: 0.822, CI: 0.69, 0.97,p = 0.027), pre-admission cognitive deterioration (assessed by IQCODE) (OR; 3.26, CI: 1.18, 9.04, p = 0.023) and depression (GDS four item: cut-off score greater than or equal to 3) (OR; 8.99, CI 1.59,50.76, p = 0.013) were identified as risk factors for developing subsequent delirium. Conclusions Despite the small size of this study our findings suggest that low, pre-morbid IGF-1 is a risk factor for subsequent delirium in this population, emphasizing the potential protective role of this anabolic cytokine and the need for replication of these findings. Copyright (C) 2005 John Wiley Sons, Ltd.