Delirium in older hospitalized patients: a decade-later study highlighting medical and medication-related etiologies beyond muscarinic antagonism.

Delirium in older adults is often due to an acute infectious insult or metabolic dysfunction. Traditionally, muscarinic antagonists have been implicated in delirium, but the association remains inconsistent. The delirium-producing effects of medications require a multifaceted understanding that goes beyond their anticholinergic actions and simultaneously considers other medical etiologies. The current study is a subgroup analysis of an 18-month prospective study on dyselectrolytemia conducted in the Department of Geriatric Medicine in a tertiary North Indian hospital. Findings are compared with those of a decade-old study from a non-geriatric service at the same hospital. Among 411 admissions, delirium occurred in 26.5% and was multifactorial in 64.2%. Infections and acute kidney injury were the leading causes. Medications were involved in 23.9%. Medication-induced delirium cases were related to severe hyponatremia or hypernatremia and direct neurological effects, in addition to usual antimuscarinic actions. However, at the study population level, while 3.3-fold higher odds of delirium were observed in patients aged 80 and above, no association was observed with the number of medications or with medications with strong anticholinergic potential. Increasing age was the strongest independent risk factor for delirium. A higher rate of medication-related causes was identified compared to past data from the same center, but different setups preclude any definite conclusions. Medication-induced delirium had a favorable outcome and was reversible in the majority. The study reinforces the role of meticulous medication review in therapeutic decision-making for older persons. The absence of an association with anticholinergic medications may be due to differences in population characteristics, limited statistical power of the study design, and evolving prescribing trends. The delirium-producing risk of individual medication classes warrants further larger studies.