Delirium is a common and serious acute neuropsychiatric syndrome with core features of inattention and cognitive impairment, and associated features including changes in arousal, altered sleep-wake cycle, and other changes in mental status. The main risk factors are old age, cognitive impairment, and other comorbidities. Though delirium has consistent core clinical features, it has a very wide range of precipitating factors, including acute illness, surgery, trauma, and drugs. The molecular mechanisms by which these precipitating factors lead to delirium are largely obscure. In this article we attempt to narrow down some specific causal pathways. We propose a basic classification for the aetiological factors: (a) direct brain insults, and (b) aberrant stress responses. Direct brain insults are largely indiscriminate and include general and regional energy deprivation (eg. hypoxia, hypoglycaemia, stroke), metabolic abnormalities (eg. hyponatraemia, hypercalcaemia), and the effects of drugs. Aberrant stress responses are conceptually and mechanistically distinct in that they constitute adverse effects of stress-response pathways which, in health, are adaptive. Ageing and central nervous system disease, two major predisposing factors for delirium, are associated with alterations in the magnitude or duration of stress and sickness behaviour responses, and increased vulnerability to the effects of these responses. We discuss in detail two stress response systems that are likely to be involved in the pathophysiology of delirium: inflammation and the sickness behaviour response, and activity of the limbichypothalamic-pituitary-adrenal axis. We conclude by discussing the implications for future research and the development of new therapies for delirium.

BackgroundTo study the prevalence of eighteen geriatric conditions in older patients at admission, their reporting rate in discharge summaries and the impact of these conditions on mortality and functional decline one year after admission.MethodA prospective multicenter cohort study conducted between 2006 and 2008 in two tertiary university teaching hospitals and one regional teaching hospital in the Netherlands. Patients of 65 years and older, acutely admitted and hospitalized for at least 48 hours, were invited to participate. Eighteen geriatric conditions were assessed at hospital admission, and outcomes (mortality, functional decline) were assessed one year after admission.Results639 patients were included, with a mean age of 78 years. IADL impairment (83%), polypharmacy (61%), mobility difficulty (59%), high levels of primary caregiver burden (53%), and malnutrition (52%) were most prevalent. Except for polypharmacy and cognitive impairment, the reporting rate of the geriatric conditions in discharge summaries was less than 50%. One year after admission, 35% had died and 33% suffered from functional decline. A high Charlson comorbidity index score, presence of malnutrition, high fall risk, presence of delirium and premorbid IADL impairment were associated with mortality and overall poor outcome (mortality or functional decline). Obesity lowered the risk for mortality.ConclusionGeriatric conditions were highly prevalent and associated with poor health outcomes after admission. Early recognition of these conditions in acutely hospitalized older patients and improving the handover to the general practitioner could lead to better health outcomes and reduce the burden of hospital admission for older patients.

In independent studies delirium was associated with higher levels of cortisol, interleukin(IL)s, and S100B. The aim of this study was to simultaneously compare cortisol, IL-6, IL-8, and S100B levels in patients aged 65years and older admitted for hip fracture surgery with and without delirium. Cortisol, IL-6, IL-8, and S100B were assayed in repeated blood samples. 120 patients (mean age 84years, 62 patients with delirium) were included. Highest levels of IL-8 (27.1, 95% Confidence Interval (CI): 13.6-53.1pg/ml) and cortisol (666, 95% CI: 475-859nmol/L) were before delirium, but of IL-6 (84.3, 95% CI: 46.5-151.4pg/mL) and S100B (0.18, 95% CI: 0.12-0.24 microg/L) during delirium. In multivariable analysis cortisol, LogIL-6, and LogS100B were significantly associated with delirium, but adjusted for pre-existing cognitive impairment, only LogS100B remained significantly associated. Cortisol, IL-6 and S100B may have a role in the pathogenesis of delirium, but S100B is the strongest independent marker.