Sex differences in inappropriate drug use: a register-based study of over 600,000 older people.

Background: Several studies have observed a higher rate of inappropriate drug use in elderly women than in elderly men, although few have focused explicitly on sex differences. Also, educational level (a measure of socioeconomic status) has been associated with both polypharmacy and inappropriate drug use in the elderly population, which could explain sex differences in inappropriate drug use.

Objective: To investigate whether sex is associated with inappropriate drug use in a large general population of older people, after adjustment for age, socioeconomic status (ie, educational level), and comorbidity (ie, number of drugs).

Methods: We conducted an analysis of data on sex, age, dispensed drugs, and education for people aged 75-89 years who were registered in the Swedish Prescribed Drug Register between July and October 2005 (N = 645,429). The main outcome measures were the filling of prescriptions for anticholinergic drugs or long-acting benzodiazepines, concurrent use of 3 or more psychotropic drugs, and potentially serious drug-drug interactions.

Results: Potentially inappropriate drug use was more common in women (24.6%) than in men (19.3%). More women than men were exposed to all types of inappropriate drug use, except for potentially serious drug-drug interactions. Logistic regression analysis showed that women were more likely to be exposed to potentially inappropriate drug use than were men (OR 1.24; 95% CI 1.23 to 1.26) after adjustment for age, education, and number of drugs (used as a proxy for comorbidity). In particular, female sex was highly associated with inappropriate psychotropic use (eg, long-acting benzodiazepines: adjusted OR [ORadjusted] 1.45; 95% CI 1.42 to 1.49; >3 psychotropic drugs: ORadjusted 1.50; 95% CI 1.47 to 1.53). In contrast, women had a lower probability of potentially serious drug-drug interactions than did men (ORadjusted 0.81; 95% CI 0.80 to 0.83).

Conclusions: Inappropriate drug use in the elderly should be monitored separately for women and men. Our results suggest that neither socioeconomic status nor comorbidity seem to explain sex differences in inappropriate drug use. Future research in other large study populations is needed for investigation of other explanations behind these sex differences.