Trends and determinants of antiresorptive drug use for osteoporosis among elderly women.Pharmacoepidemiol Drug Saf. 2005 Oct; 14(10):685-95.PD
It has been established that women who have had a first osteoporotic fracture are at a significantly greater risk of future fractures. Effective antiresorptive treatments (ART) are available to reduce this risk, yet little information is available on trends in ART drug use among the elderly. The objective is to estimate the rate ratio (RR) of having an ART prescription filled among elderly women and its relation to selected determinants from 1995 through 2001.
A cohort design was used. Through random sampling, we selected 40% of the women aged 70 years and older listed in the Régie de l'assurance maladie du Québec (RAMQ) health database. The women were grouped into four cohorts (for 1995, 1996, 1998 and 2000). January 1 was established as the index date within each cohort (1995, 1996, 1998 and 2000). The dependent variable was the RR of having at least one prescription of ART drugs filled during the year following the index date among women with and without prior use. ART users were divided in two groups: bone-specific drugs (bisphosphonates, calcitonin, raloxifen) and HRT (hormone replacement therapy). The independent variable was whether or not (control) there had been an osteoporotic-related fracture. The RR was determined for having at least one prescription of bone-specific drugs or of HRT filled during the year following the index date using a Cox regression adjusted for age, chronic disease score (CDS) and prior bone mineral density (BMD) test.
Crude rates of BMD testing (per 500 person-years) ranged from 20.4 (1995) to 41.1 (2000) in women who had had an osteoporotic-related fracture, and from 4.4 to 15.3 in controls. The crude rate of women (per 100 person-years) who had had an osteoporotic-related fracture and who took at least one bone-specific drug during follow-up ranged from 1.9 in 1995 to 31 in 2000 among those with prior osteoporotic-related fracture, and from 0.5 in 1995 to 11 in 2000 for controls; the corresponding figures for HRT ranged 6.7 in 1995 to 13 in 2000, and from 8.4 in 1995 to 11 in 2000 respectively. BMD test is the only major factor affecting the adjusted RR of having a prescription filled for bone-specific drugs (RR of 10.44; 6.91-15.79 in 1995 and RR of 3.68; 3.30-4.10 in 2000) or HRT (RR of 2.08; 1.64-2.64 in 1995 and RR of 1.44; 1.17-1.77 in 2000), particularly among women who had not had prior use. The fact of having a fracture status does significantly affect the RR of having at least one bone-specific drug prescription filled only among women without prior use (RR of 1.71; 1.26-2.33 in 1996 and RR of 1.77; 1.44-2.19 in 2000). The fact of being younger did not affect the RR of having at least one prescription of bone-specific drugs filled, but being younger increased the RR of filling a prescription of HRT.
Significant change was seen over time in the number of BMD tests ordered and ART use. Effective osteoporosis interventions are not optimal in the treatment of elderly women in a Canadian health-care system who have had an osteoporotic fracture, given that approximately 25% of women who had had an osteoporotic-related fracture were users of ART.