Adverse drug reactions and cognitive function among hospitalized older adults.

OBJECTIVE: To explore the relationship between cognitive function and the detection of adverse drug reactions (ADRs) and to evaluate whether cognitive function could influence the association between age and ADRs.
METHODS: A total of 16,926 patients admitted to 81 hospitals throughout Italy between 1991 and 1997 were included in the study. ADRs detected the during hospital stay were recorded by a study physician. Patients with a Hodkinson Abbreviated Mental Test (AMT) score <7 at hospital admission were considered cognitively impaired.
RESULTS: A total of 1,444 ADRs were diagnosed in 976 patients (5.8% of the total sample). Overall, gastrointestinal complications (18.0% of all ADRs) were the most frequent ADRs, followed by cardiovascular (12.3%) and dermatological/allergic complications (12.3%). An ADR was recorded in 232/4,883 (4.8%) patients with cognitive impairment and in 744/12,043 (6.2%) patients cognitively intact. After adjusting for potential confounders, cognitive impairment was associated with a reduced risk of ADRs (OR 0.70; 95% CI: 0.60-0.83). This result was not consistent for all types of ADRs, since the risk of neuropsychiatric complications was significantly increased among patients with cognitive impairment (OR 2.23; 95% CI 1.40-3.54). The overall rate of ADRs was 5.2% in patients younger than 65, 6.1% in patients between 65 and 79, and 5.8% in those 80 or older. When adjusting for potential confounders, not including the AMT score, age was not found to be significantly associated with ADRs. However, when the variable for the AMT score was introduced into the model, the risk for ADRs significantly increased with increasing age.
CONCLUSION: Cognitive impairment is associated with a lower detection rate of ADRs, and it represents a confounder of the association between age and ADRs.