Serum anticholinergic activity in hospitalized older persons with delirium: a preliminary study.

OBJECTIVE

To evaluate the relationship between total serum anticholinergic activity (SAA) and the presence or absence of delirium in older hospitalized persons on general medical wards.

DESIGN

Case-control study and within-subjects repeated-measures in recovered delirious patients.

SETTING

Minneapolis Veterans Affairs Medical Center medical wards.

PARTICIPANTS

Eleven male delirious patients (DSM-III-R criteria) aged 60 or older and 11 comparably aged male nondelirious controls.

MEASUREMENTS

Radioreceptor bioassay of total SAA using tritiated quinuclidinyl benzilate (QNB) binding to muscarinic receptors. Results are expressed in terms of atropine equivalents (nM).

MAIN RESULTS

Mean 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).

CONCLUSIONS

Our 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.