New data from the National Institutes of Health–funded Osteoarthritis Initiative suggest that, in some women at least, taking bisphosphonates may help to reduce the chances that there will be radiographic progression of knee osteoarthritis (OA).
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In a propensity-matched cohort analysis, women who had a Kellgren and Lawrence (KL) grade of less than 2 and who used bisphosphonates were half as likely as those who did not use bisphosphonates to have radiographic OA progression at 2 years (hazard ratio, 0.53; 95% confidence interval, 0.35-0.79). Radiographic OA progression has been defined as a one-step increase in the KL grade.
While the association appeared even stronger in women with a KL grade less than 2 and who were not overweight (HR, 0.49; 95% CI, 0.26-0.92), bisphosphonate use was not associated with radiographic OA progression in women with a higher (≥2) KL grade (HR, 1.06; 95% CI, 0.83-1.35).
“In all analyses, the effect of bisphosphonates was larger in radiographic-disease-naive individuals, suggesting protection using bisphosphonates may be more profound in those who do not already have evidence of knee damage or who have mild disease, and once damage occurs, bisphosphonate use may not have much effect,” Kaleen N. Hayes, PharmD, of the University of Toronto and her coauthors reported in the Journal of Bone and Mineral Research.
“Our study was the first to our knowledge to examine bisphosphonate exposure effects in different disease severity subgroups and obesity classifications using a rigorous, propensity-matched time-to-event analysis that uniquely addresses confounding by indication,” Dr. Hayes and her team wrote.
Furthermore, they noted that extensive sensitivity analyses, which included redoing the primary analyses to look at statin use, showed that their main conclusions were unchanged and that this helped account for any potential residual confounding, healthy-user bias, or exposure misclassification.
Study details
The Osteoarthritis Initiative is a 10-year longitudinal cohort study conducted at four clinical sites in the United States and recruited men and women aged 45-75 years over a 2-year period starting in 2004. Dr. Hayes and her coauthors restricted their analyses to women 50 years and older. Their study population consisted of 344 bisphosphonate users and 344 bisphosphonate nonusers.
The main bisphosphonate being taken was alendronate (69%), and the average duration of bisphosphonate use was 3.3 years, but no significant effect of duration of use on radiographic progression was found.
The women were followed until the first radiographic OA progression, or the first missed visit or end of the 2-year follow-up period.
Overall, 95 (13.8%) of the 688 women included in the analysis experienced radiographic OA progression. Of those, 27 (3.9%) had a KL grade of less than 2 and 68 (9.8%) had a KL grade of 2 or greater. Ten women with KL less than 2 and 27 women with KL or 2 or greater were taking bisphosphonates at their baseline visit.
“Kaplan-Meier analysis indicated that non-users and users with a baseline KL grade of 0 or 1 had 2-year risks of progression of 10.5% and 5.9%, respectively, whereas non-users and users with a baseline KL grade of 2 or 3 had 2-year of these women risks of progression of 23.0% and 23.5%, respectively,” reported the authors.
Before propensity score matching, Dr. Hayes and her colleagues observed that women taking bisphosphonates were older, had lower body weight and a higher prevalence of any fracture or hip and vertebral fractures, and were also more likely be White, compared with non-users. “In addition, bisphosphonate-users appeared to be healthier than non-users, as suggested by a lower smoking prevalence, lower average baseline KL grade, lower diabetes prevalence, and higher multivitamin use (a healthy-user proxy),” they acknowledged.