• J R Mach, M W Dysken, M Kuskowski, E Richelson, L Holden, and K M Jilk.
• Geriatric Research Education and Clinical Center (GRECC), VA Medical Center, Minneapolis, MN 55417, USA.
• J Am Geriatr Soc. 1995 May 1;43(5):491-5.

ObjectiveTo evaluate the relationship between total serum anticholinergic activity (SAA) and the presence or absence of delirium in older hospitalized persons on general medical wards.DesignCase-control study and within-subjects repeated-measures in recovered delirious patients.SettingMinneapolis Veterans Affairs Medical Center medical wards.ParticipantsEleven male delirious patients (DSM-III-R criteria) aged 60 or older and 11 comparably aged male nondelirious controls.MeasurementsRadioreceptor bioassay of total SAA using tritiated quinuclidinyl benzilate (QNB) binding to muscarinic receptors. Results are expressed in terms of atropine equivalents (nM).Main ResultsMean SAA was significantly elevated in the delirious group (mean +/- SD = 6.05 +/- 2.97 nM atropine equivalents) compared with the controls (3.38 +/- 2.49; t(20) = 2.28, P < .05). At study entry, mean SAA was significantly higher in delirious subjects whose symptoms eventually resolved completely (mean +/- SD = 7.77 +/- 2.37) compared with subjects whose delirious symptoms persisted (3.99 +/- 2.30; t(9) = 2.68, P < .05). All six patients in whom delirium resolved completely had a decrease in serum anticholinergic activity when measured during delirium (7.77 +/- 2.37) and after symptom resolution (3.92 +/- 2.61; t(5) = 3.29, P < .05).ConclusionsOur findings suggest that serum anticholinergic activity may play a role in delirium in medical inpatients. The relationships between SAA and delirium in medical patients and between total SAA and medication use warrant further study.

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