Patients need to take at least two-thirds of their osteoporosis medications over two years to reduce their fracture risk, according to research presented at the American College of Rheumatology's Annual Scientific Meeting in Boston, US this week.

The two-year Canadian study looked at 74,085 men and women aged at least 67 years starting treatment with bisphosphonates or selective estrogen receptor modulators (SERM). The researchers assessed adherence using refill compliance: the number of days of medication supplied on prescription divided by 730. They assessed fracture risk at four levels of refill compliance: 30%, 50%, 67% and 80%. There were a total of 1,751 fractures in the group.

Only compliance rates of 80% and 67% statistically reduced the number of fractures. Both levels of compliance reduced fracture risk by 15% (odds ratio (OR) 0.85). The analysis also showed that age <75 years (OR = 0.63), being female (OR = 0.54) and having had a bone mineral density (BMD) test before (OR = 0.85) or after (OR = 0.89) treatment also significantly reduced fracture risk. “Since people with osteoporosis cannot ‘see’ the benefit as they can, say, with a pain medication given to a person in pain, it helps to show them they are getting benefit through monitoring BMD,” commented study investigator Gillian Hawker, professor of medicine at Women’s College Hospital, University of Toronto.

“Patients who are at least 67% adherent with their osteoporosis medications over a two-year period are less likely to fracture,” the authors concluded. “These are important findings which confirm, at a population level, previous reports based on selected clinical trials patients. We now have evidence to show decision-makers that if we continue our efforts to monitor treatment and increase adherence, even bigger gains in fracture reduction might be possible.”

Datamonitor expects the value of the osteoporosis market to increase by 59.6% between 2007 and 2016, to US$11.1 billion. According to a report earlier this year in Drugs & Ageing (2007;24:37-55), 20% to 30% of patients taking daily or weekly drugs for osteoporosis cease therapy within 6 to 12 months of starting treatment.