Serum anticholinergic activity changes with acute illness in elderly medical patients

Background. Elevated serum anticholinergic activity levels have been associ ated with delirium in cross-sectional studies of ill older persons. This st udy used serial measures of serum anticholinergic activity levels to determ ine whether these levels change following illness resolution, and if such c hanges are specific to those with delirium. Methods. Twenty-two nursing home residents with a febrile illness had serum specimens drawn and were evaluated for the presence of delirium during the acute illness and at I-month follow-up. Delirium was diagnosed using the C onfusion Assessment Method. Serum anticholinergic activity was determined u sing a previously described radionuclide competitive-binding assay. Results. Delirium was present during illness in 8 of 22 subjects (36%), and had resolved by 1-month follow-up in all but one resident. Serum anticholi nergic activity levels were significantly higher during illness than at 1-m onth follow-up in both the delirious (0.69 +/- 0.85 nM atropine equivalents /200 mu L sample versus 0.10 +/- 0.16; p = .06) and non-delirious (0.65 +/- 0.51 nM atropine equivalents/200 mu L sample versus 0.08 +/- 0.12; p < .00 1) groups. Medication changes did not seem to be related to changes in seru m anticholinergic activity. Conclusions. In older nursing home residents with a fever, serum anticholin ergic activity appears to be elevated during illness, and declines followin g recovery from illness. This effect does not seem to be specific to those residents with delirium, nor does it seem related to medication changes.