Data from: Oral bisphosphonates are associated with increased risk of atypical femoral fractures in elderly women

Objectives: To evaluate the association between bisphosphonate use and the
risk of atypical femoral fractures among women aged 65 or older. Design:
Nested case–control study. Setting: General practice research database in
Spain. Exposures Use of oral bisphosphonates before the occurrence of
atypical fractures among cases or the corresponding index date among
controls. Bisphosphonate use was categorised as ever versus never users.
Ever users were divided according to the total time since first
prescription. Main outcome measures: Cases were defined as women aged
65 years or older with a first diagnosis of subtrochanteric or diaphyseal
fracture, recorded in the BIFAP database between 1 January 2005 and 31
December 2008, and with at least 1 year of follow-up before the index
date. For each case, five age-matched and calendar-year-matched controls
without a history of hip or atypical fracture were randomly selected from
the database. Statistical analysis: OR of atypical femoral fracture by
bisphosphonate use was determined using conditional logistic regression.
Models were adjusted for comorbidities and use of other medications.
Results: The analysis included 44 cases and 220 matched controls (mean
age, 82 years). Ever use of bisphosphonates was more frequent in cases
than controls (29.6% vs 10.5%). In multivariate analyses, OR (95% CI) of
atypical femoral fracture was 4.30 (1.55 to 11.9) in ever versus never
users of bisphosphonates. The risk increased with long-term use, with an
OR of 9.46 (2.17 to 41.3) comparing those using bisphosphonates over
3 years versus no users (p for trend=0.01). Conclusions: Bisphosphonate
use was associated with an increased risk of subtrochanteric or diaphyseal
fractures in elderly women in a low fracture risk population, with a
higher risk among long-term bisphosphonate users.