Osteoporosis is a condition characterised by low bone mass, leading to increased bone fragility and, consequently, increased fracture risk. Osteoporotic fractures are common among older, postmenopausal women and are associated with substantial morbidity and mortality.
Management strategies for women at risk include lifestyle interventions such as regular exercise, eating a balanced diet with adequate sources of calcium, and prevention of falls (The North American Menopausal Society, 2006). For women with established post-menopausal osteoporosis, drug treatment is indicated; bisphosphonates are the first-line drugs for this group (The North American Menopausal Society, 2006). With the ageing population, the incidence of osteoporosis and the need for treatment is growing.
Osteoporosis is a chronic condition and bisphosphonates are long-term medications.
Bisphosphonates are most effective when treatment is sustained for years, provided that the recommended dosage is taken for at least two-thirds of time. In practice, however, adherence to bisphosphonates is poor (Rossini et al., 2006; Papaioannou, Kennedy, Dolovich, Lau, &
Adachi, 2007; Brookhart et al., 2007; Solomon et al., 2005; Penning-van Beest, Goettsch, Erkens, & Herings, 2006). Because quitting or insufficient use of osteoporosis medication is expensive in terms of (missed) health benefits as well as ineffective expenditure, we investigated how well elderly women adhere to bisphosphonates. We also studied adherence to bisphosphonates in relation to sociodemographic, health and lifestyle characteristics obtained from ALSWH survey data. This information could help the prescribing physician to identify women at risk for inadequate adherence to treatment.
5.4.1. Uptake over time
Bisphosphonate claims were identified in the PBS by ATC coding: CM05BA/B. Claims for bisphosphonates by the Mid-age and the Older cohorts increased between 2002 and 2005, as
shown in Table 5-4. Part of this may be due to ageing, as the prevalence of osteoporosis increases over time. National statistics, however, also show an increase in bisphosphonate use (PBS prescription facts sheet, Department of Health and Ageing, 2005). Expressed as the number of defined daily doses per 1000 people per day, use increased between 2002 and 2005 as shown in Figure 5-3. Although this figure shows a different definition of bisphosphonate use for the Older cohort compared to National Statistics, their increased uptake does not appear to be solely due to ageing.
The yearly cost of the most commonly prescribed bisphosphonates (alendronic and risedronic acid) for all people in Australia, was $177,265,289 in 2005 (government and patient contribution combined). Previously subsidised under the PBS only for patients with a bone fracture due to minimal trauma, bisphosphonates are currently subsidised for all patients aged 70 years or more, with a bone mineral density measurement indicating osteoporosis (T-score of -3.0 or less). Use of bisphosphonates, and subsequently the number of PBS subsidies, which were already substantial in 2005, can therefore be expected to increase more steeply from 2007 onwards. Lowered PBS threshold, increasing awareness of bisphosphonates as drugs of choice for osteoporosis and the ageing of the population will contribute to increased use.
Table 5-4 Bisphosphonate use in the three age cohorts, per year (column percentages)
2002 2003 2004 2005 Younger cohort (n=4,376)
Yes 0 0 0 0
No 100 100 100 100
Mid-age cohort (n=7,318)
Yes 1 1 2 3
No 99 99 98 97
Older cohort (5,752)
Yes 13 16 18 20
No 87 84 82 80
a)
b)
Figure 5-3 The uptake of bisphosphonates over time; (a) among ALSWH participants and (b) national statistics
5.4.2. Longer-term use of bisphosphonates
To analyse long-term bisphosphonate use for menopausal osteoporosis, bisphosphonates coded for the treatment of Paget’s disease or hypercalcaemia of malignancy, or solely for the preservation of bone mineral density in patients on long-term glucocorticoid therapy were not included (PBS items 6371H, 6223M, 8209C, 8463K, 6343W, 6279L, 8462J, 8267D, 2920Q, 8090T, 8265B, 8482K, 4444X, 8132B). Among women in the Older cohort who consented to linkage of their Survey data to PBS data (n=5,752), 788 (14%) became new claimants of bisphosphonates between 2002 and 2005 (they started claiming it after a bisphosphonate claim free period of at least 6 months). These women had a median age of 80 years [range 76 to 84]
in 2005. By the PBS requirements at the time, all these women would be expected to have had osteoporosis and a fracture after a minimal trauma in the past. The prescription was usually issued by a GP or another primary care medical practitioner (89%) and less commonly by a rheumatologist (2%), endocrinologist (1%), internist (1%), geriatrician (1%) or other (6%).
The period of continuous use was calculated as the time from starting to claim bisphosphonates, until failing to fill a script on time.3 The median number of days of continuous use was 170 (95% confidence intervals [154 to 186]). In other words, in less than six months half the women had failed to fill a script on time (Berecki-Gisolf, Hockey, & Dobson, 2008).
Overall adherence is shown in Figure 5-4. A sharp decrease is seen at the start of claiming for bisphosphonates; this corresponds with failure to fill the second (8%) script; 20% failed in timely script filling before the third script.
Figure 5-4 The declining percentage of Older women who continued with timely bisphosphonates claims
Women’s characteristics were analysed in relation to continuous claiming (or time to first failure to fill a prescription). Smoking was associated with failing to fill a prescription, as was former smoking (Figure 5-5, top). Adherence was better among women who reported high levels of physical activity compared to those with low levels (Figure 5-5, middle). Alcohol consumption and body mass index were not associated with failing to fill a prescription. Failure to fill scripts was also not associated with level of education, rurality, marital status, the ability to manage on available income, frequency of visiting a GP, or health (in terms of the number of chronic
3 ‘On time’ script filling allows a gap of two weeks between running out of medication and picking up a refill from the pharmacy. The rationale for this ‘maximum allowed gap’ is that because each script lasts for a month, filling the next script after a break of more than two weeks means treatment coverage of less than two-thirds. In other words, adherence is defined as the time until medication use drops below two-thirds of the prescribed dosage.
conditions, prior use of non-osteoporosis medication, body mass index and SF-36 scores for physical functioning, bodily pain, general health, vitality and mental health).
Heartburn and abdominal pain are commonly reported as side-effects of bisphosphonates. This effect may be due to a high prevalence of heartburn among elderly women with osteoporosis rather than a medication effect (P. D. Miller et al., 2000). Medications for conditions such as heartburn and stomach ulcer (ATC codes A02BA/B/C/X) were claimed by 44% of women in the six months prior to commencing to claim bisphosphonates. These women were less likely to continue claiming bisphosphonates in the longer term (Figure 5-5, bottom). A similar pattern was seen in women who reported often having heartburn before starting to claim bisphosphonates, but who did not claim prescribed (PBS) medication for acid-related disorders.
Figure 5-5 The declining percentage of women who are still continuous users, in relation to smoking, levels of physical activity and heartburn
Determining if adherence to bisphosphonates is affected by medication out-of-pocket cost was made difficult by the safety net. It is a chicken-and-the-egg problem: women who generally adhere to medication are more likely to reach the safety net threshold; subsequently lowered cost might be an incentive to adhere to medication. Most of the women were concession card holders (94%). Taking into account safety net status, having a concession card was not related to claiming bisphosphonates, neither was the reported ability to manage on the available income. In short, among Older women eligible for bisphosphonate benefits, affordability did not appear to determine adherence.
In conclusion, Older women who participated in the ALSWH and consented to linkage to pharmaceutical claims data showed poor long-term adherence to bisphosphonates. Within six months, half the women stopped making timely claims. Women who smoked or took acid-related medication or who had gastro-intestinal symptoms prior to starting bisphosphonates were less likely to continue claiming bisphosphonates while women who reported high levels of exercise were more likely to continue, suggesting that enquiry about health behaviour and symptoms could alert the prescribing physician to women at risk for adherence failure.