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AIMS: To evaluate the association between noncompliance with alendronate and risedronate and the risk of nonvertebral osteoporotic fracture in community-dwelling elderly women.

METHODS: A nested case-control study was conducted using the Quebec administrative health databases. To be included in the cohort, women needed to be aged >= 68 years and to have initiated treatment with alendronate or risedronate between 1 January 2002 and 31 March 2005. Cases consisted of all women with an incident nonvertebral osteoporotic fracture occurring >= 1 year after initiation of therapy. Each case was matched with up to 20 controls using incidence density sampling, according to age ( /- 1 year) and follow-up duration. A woman was noncompliant if she had a medication possession ratio (MPR) <80% for total follow-up duration. Rate ratios (RR) for fracture were estimated through conditional logistic regression analysis, adjusting for potential confounders.

RESULTS: Among the 30 259 women included in the cohort, 1036 nonvertebral fracture cases were identified and were matched to 20 069 controls. Compared with women with a MPR >= 80%, those with a MPR < 80% had a greater risk of nonvertebral fracture [adjusted RR 1.27, 95% confidence interval (CI) 1.12, 1.44]. Considering hip fracture only, the multivariate model yielded similar results, (adjusted RR 1.28, 95% CI 1.02, 1.61).

CONCLUSIONS: Among community-dwelling elderly women, noncompliance with alendronate or risedronate is associated with an increased risk of nonvertebral fracture.

Copyright (C) 2008 Blackwell Publishing Ltd.