Importance of serum anticholinergic activity in the assessment of elderly patients with delirium

To evaluate the importance of serum anticholinergic activity (SAA) in elderly patients who developed delirium following hospital admission, we performed a cross-sectional study with consecutively referred inpatients in a university geriatric medical ward. Sixty-one patients aged 66 to 95 years (mean age: 79.2 +/- 11.6; 54% females) were recruited. Delirium was assessed by means of the Confusion Assessment Method, SAA determination, questionnaire for current drug treatment, past medical history and clinical examination, and blood chemistries. Patients were divided into two groups according to the absence (N = 49) or the presence (N = 12) of delirium. Delirious patients showed a significantly higher SAA(23.0 vs 3.9 pmol/mL atropine equivalents, P < .004); they were using antibiotics (P < .05), neuroleptics (P < .002), barbiturates (P < .004), and benzodiazepines (P < .005) more frequently. Subjects with delirium were more likely to have infections and a lower Body Mass Index; they had higher plasma glucose and creatinine. The multivariate analysis identified SAA and use of neuroleptics, and benzodiazepines as the most important features independently associated with delirium. SAA may be a suitable marker for identifying people at risk of developing delirium. Moreover, neuroleptics and benzodiazepines must be carefully used in the elderly because of their relationship with the onset of delirium.