Bone mineral density measurement and osteoporosis treatment after a fragility fracture in older adults: regional variation and determinants of use in Quebec

Osteoporosis (OP) is defined as a skeletal disorder characterized by reduced bone strength which predisposes a person to an elevated risk of fracture [1]. This disease is an important public health problem in societies with an ever-increasing proportion of elderly people. It is projected that in Canada, approximately one in four women and one in eight men will suffer from OP during their lifetime [2]. Fragility fracture is the main adverse consequence of this disease.

Fragility fracture is defined by the World Health Organization as "a fracture caused by injury that would be insufficient to fracture a normal bone...the result of reduced compressive and/or torsional strength of bone" [3]. Clinically, a fragility fracture may be defined as a fracture "...that occurs as a result of a minimal trauma, such as a fall from a standing height or less, or no identifiable trauma" [4]. Typical fractures in patients with osteoporosis include vertebral (spine), proximal femur (hip), distal forearm (wrist) and proximal humerus [4, 5].

The number of fragility fractures is expected to increase over the next 20 years in Canada; in 2041, the number of forecast hip fractures will be 88,124, a 3-fold increase from 1993–94 [6]. Hip and vertebral fractures are associated with a particularly high level of morbidity and mortality [7–10]. One-year survival rates following a hip fracture are reduced [11, 12]. In addition, individuals who have already sustained one fracture are at high risk for recurrence [13–17].

Fragility fractures lead to extensive use of health care resources and high costs of care [18–23]. Since 1998 [24], the Osteoporosis Society of Canada recommends using bone mineral density (BMD) measurement to confirm diagnosis of osteoporosis [3]. Various drugs are considered effective for the treatment of osteoporosis; such as hormonal replacement therapy and bisphosphonates (etidronate and alendronate) [3, 25]. During our study period, from January 1999 to December 2000, the province of Quebec's health insurance plan (RAMQ) was offering unrestricted coverage for osteoporosis treatments; namely hormone replacement therapy (HRT), the bisphosphonates etidronate and alendronate, the selective modulator of estrogen receptors raloxifene and calcitonine nasal spray [26].

In developed countries, awareness and use of clinical guidelines by physicians is low. This can be partially explained by the lack of uniformity in recommendations [27]. In a large retrospective study, Solomon et al [28] found that the following patient variables lowered the probability of a physician's adherence to guidelines and thus patients in these categories were less likely to receive either BMD testing or OP treatment: patients aged >74 years (odds ratio [OR] = 0.49; 95% confidence interval [CI]: 0.43 to 0.55); patients aged < 55 years (OR = 0.34; 95% CI: 0.28 – 0.42); men (OR = 0.17; 95% CI: 0.12 – 0.23); black patients (OR = 0.40; 95% CI: 0.34 – 0.47), and patients with multiple comorbidities (OR = 0.79; 95% CI: 0.69 – 0.89). In another study, patient variables such as female gender, glucocorticoid use, and receipt of care from a rheumatologist all increased the likelihood of receiving BMD [27].

The failure to adhere to OP diagnosis and treatment guidelines results in missed opportunities for preventing new fractures [19, 21, 22]. A review article examining OP investigation, treatment and interventions following a fragility fracture in different countries concluded that [29] "Investigation of OP by bone mineral density was low: 14 to 16 studies reported investigation of less than 32% of patients." This same study revealed that even when diagnosis of OP was confirmed, only a fraction of patients were receiving calcium and vitamin D supplements (8 – 62%) and bisphosphonates (0.5 – 38%). In Canada, the proportion of patients with fragility fractures who receive a BMD test or a physician diagnosis of OP ranges widely from 1.7 to 50% [21]. Moreover, only 5.2 to 37.5% of patients with fragility fractures receive pharmacotherapy (HRT, bisphosphonates or calcitonine) for their osteoporosis [21].

One of the factors contributing to low BMD testing in Canada may be the low geographical accessibility to specialized BMD equipment and trained personnel. This was well documented in two studies examining the patterns of use of BMD in Ontario [30, 31]. In the first, the age-adjusted rate of BMD testing for the 1996–1998 time period in 49 Ontario counties varied from 0.2 to 47.1 per 1000 women [30]. Regional rate variation analyses of BMD performed during that same period indicated a 235-fold variation in BMD testing across counties, these rates being much higher in urban, south-central regions than in rural northern Ontario. According to this study, the large variation of access to BMD testing correlated directly with the location of BMD devices [32]. This urban/rural difference was also observed in a survey of Ontario general practitioners in which physicians with urban practices reported a higher use of BMD than their rural counterparts.

In 2001, 71 BMD devices were available in the province of Quebec; nearly half of these were located in Montreal. To our knowledge, regional variations in the diagnostic process and treatment of OP have not yet been studied within the province of Quebec.

The main objectives of this study were to estimate the BMD testing rate and OP treatment rate for people over 65 years of age who had already suffered from a fragility fracture, and to examine how the location of residency is related to BMD testing and OP treatment. We sought to identify potential predictors of BMD testing in the two years following a fragility fracture, as well as predictors of OP treatment in the year following the index fracture.

In 1999 and 2000, a total of 29,417 individuals aged 65 years or older consulted for a vertebral, hip, wrist or humerus fracture. Among them, 3140 had a fragility fracture within two years prior to the index date, 331 had an accident in the week preceding the index date and 94 had either incomplete data relating to the residence codes or were living in Northern Quebec. After exclusions, the cohort consisted of 25,852 individuals, 77% of which were women.

Tables 2 and 3 display age-adjusted BMD testing rates and OP treatment rates after a fragility fracture, as well as mean and median aerial distance between residency and BMD device localization, for women and men, respectively. These tables also include the smoothed rates of BMD testing and OP treatment. These smoothed rates take into account the spatial nature of the data such as the neighboring regions. Figure 1 and Figure 2 display cartographic representations of age-adjusted BMD testing rates for women and men, respectively. There is a clear gender and regional variation in the use of BMD testing in favor of women and the most populated regions. For women, BMD testing rate varies from 0.3% in Abitibi-Témiscamingue region to 16.1% in Quebec City region, while for men it varies from 0% in North Shore region to 6.1% in Quebec City region. Regarding OP treatment, the regional variation is statistically significant but is less important than in the BMD testing rates. For women, OP treatment varies from 25.1% in Outaouais region to 39.9% in Eastern Townships region, whereas for men, OP treatment varies from 6.8% in Laurentians to 15.2% in Eastern Townships region.

Region	Dist. BMD (km) mean (median)*	BMD (%)*	BMD SR (%)	OPT (%)*	OPT SR (%)
Eastern Townships	18.0 (12.9)	16.1	15.8	39.9	33.2
Chaudière-Appalaches	27.1 (19.7)	14.9	14.7	35.4	34.3
Montérégie	8.8 (3.8)	14.7	14.6	31.4	30.6
Laval	3.4 (3.3)	14.6	14.5	28.8	29.8
Montreal-Center	2.0 (1.7)	14.4	14.5	26.1	29.8
Lanaudière	22.6 (12.1)	13.4	13.0	29.2	29.3
Quebec City	10.0 (2.0)	13.2	13.7	29.3	31.8
Mauricie, Central Qc	19.8 (4.5)	12.9	12.9	29.5	29.6
Laurentians	29.9 (12.8)	11.7	12.0	30.8	28.7
Outaouais	24.5 (5.4)	9.4	9.8	25.1	28.0
Saguenay-Lac-St-Jean	26.3 (13.2)	8.8	9.7	38.9	34.1
North Shore	271.4 (314.4)	4.2	3.5	30.0	30.3
Lower St. Lawrence	85.7 (74.6)	2.3	3.7	34.4	33.6
Gaspé, Magdalen Island	331.0 (322.6)	1.1	1.9	32.3	31.9
Abitibi-Témiscamingue	88.9 (92.5)	0.3	3.9	25.9	27.4

* The difference between regions is statistically significant (p < 0.0001)

Region	Dist. BMD (km) mean (median)*	BMD (%)**	BMD SR (%)	OPT (%)*	OPT SR (%)
Quebec City	10.0 (2.0)	6.1	5.4	9.0	11.3
Montérégie	8.8 (3.8)	5.7	5.3	11.7	10.6
Lanaudière	22.6 (12.1)	5.5	5.0	13.3	10.0
Eastern Townships	18.0 (12.9)	5.4	5.3	15.2	12.1
Laval	3.4 (3.3)	5.4	5.3	9.9	10.2
Montreal-Center	2.0 (1.7)	4.9	5.3	6.9	10.2
Mauricie, Central Qc	19.8 (4.5)	4.5	4.8	10.5	10.4
Chaudière-Appalaches	27.1 (19.7)	4.4	5.1	13.6	12.5
Outaouais	24.5 (5.4)	3.9	3.7	8.5	9.5
Laurentians	29.9 (12.8)	3.6	4.2	6.8	9.5
Saguenay-Lac-St-Jean	26.3 (13.2)	3.5	3.9	12.5	11.7
Gaspé, Magdalen Island	331.0 (322.6)	1.7	1.1	9.1	11.7
Abitibi-Témiscamingue	88.9 (92.5)	0.7	1.9	10.9	9.7
Lower St. Lawrence	85.7 (74.6)	0.4	1.5	14.5	12.0
North Shore	271.4 (314.4)	0.0	0.8	12.2	11.7

* The difference between regions is statistically significant (p < 0.0001)

** The difference between regions is not statistically significant (p = .0578)

Logistic regression analyses (Table 4) show that women who had a prior BMD testing two years before the index date (OR: 2.45), who had a vertebral fracture (OR: 2.09), and who were exposed to OP treatment the year preceding the index date (OR: 1.51), were all more likely to be exposed to BMD testing. On the other hand, women aged 80 or older (OR: 0.17), women living in long-term care facilities (OR: 0.04), women with multiple comorbid conditions (OR: 0.98), and finally, women living over 105 km from the nearest BMD location (OR: 0.28), were less likely to undergo a BMD testing. Similarly, women who, prior to their fragility fracture, received an OP treatment (OR: 13.6) or a long-term glucocorticoid therapy (OR: 1.45), or who were tested for BMD (OR: 2.10), as well as those with a vertebral fracture (OR: 4.22), were more likely to obtain OP treatment in the year following the fracture. On the contrary, women aged 80 or older (OR: 0.60) were less likely to obtain such a treatment.

As in other studies, we found a low rate of BMD testing in high risk patients. Only 11% (13% of women and 5% of men) of patients having suffered from a fragility fracture were tested for osteoporosis or were tested to monitor response to therapy in the two years following their fracture. These results are comparable to the 0 to 32% [29] and 1 to 32% [27] frequencies of testing post-fragility fracture reported in large review papers. In our study, we found that BMD testing is not completely explained by a patient's physical access to densitometers. Gender, age and social status also seem to influence the rate of BMD testing.

Further, we found a moderate rate of OP treatment after a fragility fracture. A total of 25% (30% of women and 10% of men) of patients received an OP treatment in the year following the fracture. This is comparable with results from a review paper, which reported rates of bisphosphonate use ranging from 0.5% to 38% [29].

Finally, we found regional disparities in BMD testing according to the socio-demographic variables examined. For instance, age-adjusted BMD testing rates found in our study were statistically different among regions, varying from 0.3 to 16.1% for women and from 0 to 6.1% for men.

Hajcsar et al [49] had previously depicted gender differences in the investigation frequencies of osteoporosis. They reported a 1-year BMD testing rate of 24% for women and only 8.3% for men. These differences between our results and those reported by Hajcsar et al can be attributed to population and study design differences.

As reported in Jaglal [32], the accessibility to BMD testing seems to be strongly related to the use of a BMD device. Our results however show that the distance from residence to the nearest BMD device is neither the only nor the most important predictor of BMD testing. Younger age, previous BMD testing, and previous OP treatment use increased the likelihood of BMD testing, whereas social status, such as living in a long term care facility or being recipient of a guaranteed income supplement, decreased the likelihood of BMD testing. This last observation, not reported in other papers, was obtained by using a unique governmental data base that permits analysis of the above-mentioned social variables.

In the review papers cited above, patient characteristics were reported to influence BMD testing. In a study at two primary care practices affiliated with an academic medical center, Solomon et al found that some patient variables significantly lowered the probability of a physician's adherence to local guidelines (including BMD testing and OP treatment). Old age and young age as opposed to middle age, male sex, black race, and having more than one comorbid condition were associated with a decreased likelihood of undergoing a BMD testing or receiving an OP medication [28]. Our results are concordant with these reported findings concerning old age and gender but not regarding comorbidity. Comorbidity, as defined by the number of distinct medications taken in the year preceding the fracture, was negatively correlated with BMD testing for women, but was positively correlated with future OP treatment. In Solomon et al [28], these two outcomes were merged, although the authors argued that they had observed similar results when they were examined separately. With regards to comorbidity, the difference between our results and those reported by Solomon et al are likely due to differences in the methodology used and populations studied. For instance, comorbidity was defined differently in the two studies. Moreover, our analysis was population-based whereas Solomon et al studied patients seen in primary care practices affiliated with an academic medical center. Health care provided in academic centers may not be representative of the care provided to the general population.

Regarding therapy used to prevent recurrent fractures, our results showed that positive predictors for receiving treatment for both men and women were vertebral fracture, prior BMD testing, prior OP treatment, and long-term glucocorticoid use, as defined in the method section. Men with wrist fractures and women with hip or humerus fractures were less likely to be treated than individuals with fractures at other sites. These results are concordant with those of other studies [21, 29]. The very low BMD testing rate in patients living in long-term care facilities suggests an important care gap in the management of OP in those facilities.

One might argue that patients may have died before receiving BMD testing or OP treatment. This would explain the lower rate of care observed in long term care facilities patients. In order to verify the stability of the associations between predictors and outcomes, we performed analyses on surviving patients during the two years following their fracture. These models showed similar results in predictors of BMD testing and OP treatment, except for site of fracture, for which we observed lower odds ratios. Exclusion of other predictors, such as prior BMD testing and prior OP treatment showed similar results between predictors and outcomes, except for long-term glucocorticoid use. Indeed, since patients who had received a long-term glucocorticoid therapy may have been already tested and/or treated for OP, the removal of these variables increased the associated OR.

We observed high death rates of 23% in women and 35% in men 2 years following fragility fracture. This is a 3-fold increase in death rates compared to those observed in the general elderly population for the year 2001 [50]. The 1-year death rate of the population aged 65 or older in Quebec in 2001 was 3.9% for women and 4.9% for men. An increase in mortality rates following fragility fracture was also reported in other studies [11, 12].

A major strength of this study is its population based design. Moreover, to obtain a more comprehensive model explaining BMD use, we included a geographical distance variable in the modeling process. The major limitation of this study is inherent to the use of administrative databases. On the one hand, we may have underestimated the incidence of fragility fractures as some of these, such as vertebral fractures, are notoriously under-diagnosed by physicians [51]. We may also have overestimated incidence of fragility fractures since we inferred that all fractures not associated with a high velocity trauma were fragility fractures. However, in an unpublished pilot study, we found a positive predictive value of 79% for fragility fracture diagnosis based on this definition [35]. One of the limitations regarding the use of the guaranteed income supplement as a social status indicator includes a possible under-estimation of the number of beneficiaries in this category, as nearly 31% of individuals in Canada who are admissible for a guaranteed income supplement do not benefit from it [52]. Furthermore, as we have excluded fragility fractures within the 2 years prior to the index date we may have excluded at risk patients. Unfortunately, we are limited by the fact that data before the year 1997 are unavailable. It is well known that physician characteristics may affect the incidence of BMD testing [27, 28]. Although we acknowledge the importance of studying physician characteristics in the modeling process, we were unable to retrieve such data for technical reasons.