Longitudinal patterns of new Benzodiazepine use in the elderly

To characterize longitudinal patterns of Benzodiazepine use in the elderly.

Prospective cohort of 78 367 community-dwelling Quebec residents aged 66 years or more who were new Benzodiazepine users, was followed for 5 years, 1989-1994. Data acquired from four population-based, provincial administrative databases were used to create time-dependent measures of change in dosage, switching or adding Benzodiazepines for 11 drugs listed in the provincial formulary. Subject-specific Spearman's rank correlation coefficients between dose and time were used to measure the tendency of increasing dose with consecutive periods of use. Multiple logistic regression and generalized estimating equations (GEE) models evaluated subject characteristics associated with increasing dose.

The mean duration of uninterrupted Benzodiazepine use was 75.5 days. The mean daily dose was about half the recommended adult daily dose but 8.6% of subjects exceeded the recommended adult dose. Some of them (28.8%) switched medications at least once and 8.2% filled two or more prescriptions concurrently. For women, older age at date of first prescription was associated with increasing dose over time (odds ratio (OR) for 10 year age increase = 1.23, p < 0.001).

Long periods of Benzodiazepine use are frequent among Quebec elderly. The evidence of increasing dose, particularly for older women, and long-duration of use has important implications for clinicians.