Bisphosphonates reduce the risk of fracture in older women who have osteoporosis, but they have potential adverse effects. This treatment, therefore, is most successful when given to women who are most likely to benefit from it. Researchers conducted a meta-analysis of randomized clinical trials involving bisphosphonates to evaluate the time to benefit for the prevention of nonvertebral and other fractures in postmenopausal women with osteoporosis.

The authors included studies of postmenopausal women with a diagnosis of osteoporosis based on either an existing vertebral fracture or a bone mineral density T score of -2.5 or lower. Only studies of alendronate, risedronate, and zoledronic acid were included because they are guideline-recommended, first-line treatments for the reduction of nonvertebral fractures in postmenopausal women with osteoporosis.

Ten trials with data on 23,384 women were included in the meta-analysis. The mean age of the women ranged from 63 to 74 years, most were White, and follow-up ranged from 12 to 48 months. The analysis showed that 100 postmenopausal women with osteoporosis would need to be treated with bisphosphonates for 12.4 months to prevent one nonvertebral fracture. The time to benefit for the outcomes of hip fracture, any clinical fracture, and clinical vertebral fracture were similar. The findings suggest that bisphosphonate therapy is most likely to be beneficial in women who have a life expectancy of longer than 12.4 months.

The study had several limitations, including that some trials used dosing regimens that differed from those commonly prescribed, results may not be generalizable to populations other than those represented in the trials, and short- and long-term harms weren't estimated by the researchers.

The potential short-term harms and burdens of bisphosphonate therapy should be balanced against delayed benefits when discussing treatment options for older postmenopausal women, the authors advise. Given that most postmenopausal women have a life expectancy that is substantially greater than 12.4 months, they conclude that bisphosphonate therapy is likely to be beneficial for most older women who have osteoporosis.