Antidepressant and anxiolytic medications and risk of mortality in people with dementia: a nested case-control study in Northern Ireland

Background
Antidepressant and anxiolytic medication use in people with dementia (PwD) may contribute to potentially inappropriate prescribing and be associated with mortality.

Objective
To investigate trends in prescribing of these medications and their association with mortality risk among PwD.

Methods
A nested case-control study was conducted in Northern Ireland (NI) using linkage of five administrative population-based data sources within a cohort of dementia patients (identified if a medication indicated for dementia was prescribed). Dementia patients who died were matched to one control who lived at least as long as their matched case after dementia diagnosis (matched on age, sex and year of dementia). Exposure to antidepressant and anxiolytic medications was assessed from two years prior to study entry. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using conditional logistic regression after adjusting for demographic factors and comorbidities.

Results
The study included 14,420 dementia cases. Antidepressants were prescribed to 59.2% of cases and 54.7% of controls whilst 44.8% of cases and 36.0% of controls were prescribed anxiolytics. There was evidence of a weak increased risk of mortality in PwD prescribed antidepressants (fully adjusted OR=1.08; 95% CI 1.02-1.14) and a strong increased risk in those prescribed anxiolytics (fully adjusted OR=1.26; 95% CI 1.19-1.33) compared to nonusers.

Conclusions
In this large NI population-based cohort of PwD, elevated levels of antidepressant and anxiolytic prescribing were observed. The use of anxiolytic medications was strongly associated with mortality in PwD.