Risk Factors for Proximal Humerus, Forearm, and Wrist Fractures in Elderly Men and Women The Dubbo Osteoporosis Epidemiology Study

Tuan V. Nguyen1,2, Jacqueline R. Center1, Philip N. Sambrook1,3 and John A. Eisman1

1 Bone and Mineral Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, Australia.
2 Present address: The Simpson Centre, University of New South Wales, Liverpool Hospital, Liverpool, New South Wales, Australia.
3 Present address: Department of Rheumatology, Royal North Shore Hospital, St. Leonards, New South Wales, Australia.


    ABSTRACT
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Fractures of the proximal humerus, forearm, and wrist account for approximately one third of total osteoporotic fractures in the elderly. Several risk factors for these fractures were evaluated in this prospective study of 739 men and 1,105 women aged >=60 years in Dubbo, Australia. During follow-up (1989–1996), the respective incidences of humerus and of forearm and wrist fractures, per 10,000 person-years, were 22.6 and 33.8 for men and 54.8 and 124.6 for women. Independent predictors of humerus fracture were femoral neck bone mineral density (FNBMD) (relative risk (RR) = 2.3, 95% confidence interval (CI): 1.2, 4.5) in men and FNBMD (RR = 2.4, 95% CI: 1.7, 3.5) and height loss (RR = 1.1, 95% CI: 1.0, 1.2) in women. For forearm and wrist fractures, risk factors were FNBMD (men: RR = 1.5, 95% CI: 1.0, 2.3; women: RR = 1.5, 95% CI: 1.2, 1.9) and height loss (men: RR = 1.2, 95% CI: 1.0, 1.3; women: RR = 1.1, 95% CI: 1.0, 1.2). In addition, dietary calcium (men: RR = 2.0, 95% CI: 1.0, 3.6) and a history of falls (women: RR = 1.9, 95% CI: 1.4, 2.6) were also significant. These data suggest that elderly men and women largely share common risk factors for upper limb fractures and that FNBMD is the primary risk factor.

aged; bone density; forearm; fractures; humeral fractures; humerus; osteoporosis; prospective studies

Abbreviations: BMD, bone mineral density; CI, confidence interval


    INTRODUCTION
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Research in the last three decades has concentrated on identification of risk factors for hip fractures in elderly women, the most serious consequence of osteoporosis. However, hip fractures account for only one third of the total incidence of fractures in the elderly population. An equal percentage of fractures actually occurs at the humerus, forearm, and wrist (1Go, 2Go). Although these fractures result in only a modest increase in morbidity compared with that for hip fracture, they account for considerable health care costs, and at a relatively younger age (3Go).

In contrast to the intensive research into risk factors for hip fractures, little is known about risk factors for humerus, forearm, and wrist fractures. Case-control and cross-sectional studies have shown that women who suffer forearm fractures have slightly lower bone mineral density (BMD) in the forearm than controls do (4GoGo–6Go). However, the difference could be due to bone loss after the fracture. Low BMD and neuromuscular impairment are independent predictors of fracture risk in women (7Go). Those women in the lowest quintile of BMD have a fourfold and sevenfold increased incidence of distal forearm and proximal humerus fractures, respectively (8Go). The incidence and determinants of upper limb fractures in men have not been studied systematically.

The present study addressed two specific issues: 1) what are common and independent risk factors for humerus, forearm, and wrist fractures in men and women; and 2) how much of this fracture risk can be attributed to these factors?


    MATERIALS AND METHODS
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Subjects
The present analysis was part of the Dubbo Osteoporosis Epidemiology Study, whose design and population have been described previously (9GoGo–11Go). Briefly, in 1989, all men and women aged 60 years or more living in Dubbo, a city of approximately 32,000 people 400 km northwest of Sydney, Australia, were invited to participate in the study. The target population comprised 1,581 men and 2,095 women aged 60 years or more who were 98.6 percent Caucasian and 1.4 percent indigenous Aboriginal. Clinical risk factors for osteoporosis, BMD, and measures of propensity to falls were assessed prospectively. Dubbo was selected for the study site because the age and sex distribution of the population closely resembles that of the Australian population. In addition, the city is relatively isolated in terms of medical care, so that virtually complete ascertainment of all fractures occurring in the target population is possible.

The Dubbo Osteoporosis Epidemiology Study is an ongoing investigation; by December 1997, 868 men and 1,383 women had participated. The present analysis was limited to men and women in the study sample who had had a proximal humerus, forearm, or wrist fracture and for whom clinical data, including BMD and fall-related measurements, were complete prior to the fracture event. Also included were those persons in the sample who had not had any fracture. On the basis of these criteria, 739 men and 1,105 women were included in the analysis. For these subjects, the total length of follow-up was 6,194 person-years for men and 8,026 person-years for women. The median duration of follow-up for men and women was 7.3 and 7.8 years, respectively. The study was approved by the St. Vincent's Hospital Committee (Sydney), and all subjects gave written informed consent.

Assessment of risk factors
After informed consent was obtained, subjects were interviewed by a nurse coordinator. The coordinator administered a structured questionnaire to collect data such as age and anthropometric variables, including current height and weight. Height loss was estimated as the difference between current height and peak height (lifetime maximum height). Lifestyle factors such as past and present tobacco use (assessed as pack-years) and alcohol consumption were elicited. Dietary assessment was based on a frequency questionnaire for calcium intake, which has been validated previously (12Go). Physical activity was assessed by using a questionnaire similar to that for the Framingham Heart Study (13Go), in which each subject estimated the number of hours per day spent on five levels of physical activity: basal activity, sedentary, light, moderate, and heavy. A weighting or intensity factor (13Go) based on the approximate oxygen consumption needed for each level of activity was multiplied by the number of hours engaged in each level of activity. The weighting factors were as follows: 1, basal activity; 1.1, sedentary; 1.5, light; 2.4, moderate; and 5, heavy. The resulting products for all activities were then summed to yield an index of total physical activity. A high index corresponds to a physically active lifestyle, and low levels correspond to habitual inactivity.

Subjects were asked to recall the number and cause of falls in the last 12 months. Falls caused by external forces (e.g., being struck by a moving vehicle) were excluded from the analysis. Various tests of postural stability were performed on each subject at baseline, as described previously (14Go). Quadriceps strength (maximum isometric contraction) was measured in the sitting position in the subject's dominant (stronger) leg by using a horizontal spring gauge calibrated to as much as 50 kg of force. Body sway, assessed by using a simple swaymeter that measured displacement of the body at waist level in 30-second periods, was measured under four test conditions: 1) eyes open, firm surface (wooden floor); 2) eyes closed, firm surface; 3) eyes open, compliant surface (15 cm deep, high-density foam); and 4) eyes closed, compliant surface. Full descriptions of the apparatus and procedures used, along with test-retest reliability scores (and confidence intervals) for the test measures, have been reported previously (14Go).

Measurement of BMD
BMD (g/cm2) was evaluated in the lumbar spine and femoral neck by dual energy x-ray absorptiometry using a LUNAR DPX-L densitometer (LUNAR Corporation, Madison, Wisconsin). The radiation dose with this method is <0.1 µGy. The coefficients of reliability of BMD measurements at St. Vincent's Hospital were 0.98, 0.95, and 0.96 in the lumbar spine, femoral neck, and total body, respectively (15Go).

Ascertainment of fractures
Symptomatic humerus, forearm, and wrist fractures occurring during the study period were identified in residents of the Dubbo local government area by using radiologists' reports from the only two centers providing radiography services, as described previously (11Go). Fractures were included only if the report of fracture was definite and, on interview, the fracture was reported to have occurred with minimum or no trauma, including a fall from a standing height or lower. Fractures clearly due to major trauma such as motor vehicle accidents were excluded from the analysis.

Preliminary analyses indicated that many of the clinical characteristics of forearm and wrist fractures, such as BMD, quadriceps strength, body sway, and age, are common. Therefore, these fractures were combined into a single fracture group.

Statistical methods
Differences in the baseline characteristics of fracture and nonfracture subjects were tested by using the t test or the likelihood ratio chi-square test, as appropriate. Incidence rates of fractures, calculated for males and females separately as the number of fractures occurring during the study period divided by the number of person-years over the same period, were expressed per 10,000 person-years. A 95 percent confidence interval around the incidence was constructed by using the Poisson distribution. The study period was defined as the interval between the baseline and follow-up (December 1997) visits or, in the case of death, between baseline and the date of death.

To identify potential predictors of fracture risk, a Cox proportional hazards model (16Go) was used. In this model, time to fracture (dependent variable) was expressed as an exponential function of several risk factors. Final models were constructed by using stepwise and backward elimination algorithms (17Go). The significance of parameter estimates derived from the Cox proportional hazards model was tested with the likelihood ratio statistic (18Go). Before the model was constructed, a relatively high p value (0.15) was used for the immediate steps to include the effects of any potentially important variables that might be statistically nonsignificant because of the size (and resulting power) of the study. The assumption of proportional hazards for the levels of each risk factor was evaluated in relation to the linearity of plots of log(–log(S(ti)j), where S(ti)j describes the jth survival time for the ith level (i = 1, 2) of each risk factor.

Further analyses were based on factors identified in the "final" Cox regression model. Each factor was dichotomized into two classes to represent high and low risk categories. For example, in terms of BMD, a subject was classified as osteoporotic if his or her BMD was 2.5 standard deviations or more below the young normal level or as normal. The "young normal" BMD was obtained from a sample of 52 Australian men and women aged 20–32 years. Men and women were classified as osteoporotic if their BMD was <0.74 and <0.7 g/cm2, respectively. Those with a femoral neck BMD of more than 1 standard deviation below but less than 2.5 standard deviations below the young normal mean were classified as osteopenic (men, 0.74–0.92 g/cm2; women, 0.70–0.88 g/cm2). The relative risk for the class of each risk factor was estimated by using the Cox proportional hazards model. All database management and statistical analyses were performed via the SAS Statistical Analysis System (19Go).


    RESULTS
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Incidence of fractures
During the follow-up period, 179 subjects (35 men and 144 women) suffered humerus, forearm, and wrist fractures. These fractures accounted for 19 and 31 percent of the total fractures in men and women, respectively. The overall incidence of humerus fractures in women was 54.8 per 10,000 person-years (95 percent confidence interval (CI): 38.6, 71.0), more than twice the incidence in men (22.6 per 10,000 person-years, 95 percent CI: 10.8, 34.4). However, the incidence of forearm and wrist fractures was much higher (men: 33.8 per 10,000 person-years, 95 percent CI: 16.1, 51.6; women, 124.6 per 10,000 person-years, 95 percent CI: 96.2, 153.0). For humerus fractures, the incidence increased with advancing age in both men and women, with the risk being the highest in the group aged 80 years or more. For forearm and wrist fractures, the trend was apparent in women but not in men (figure 1).



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FIGURE 1. Incidence of humerus fractures (left panel) and of forearm and wrist fractures (right panel), expressed as fracture cases per 10,000 person-years (p-yrs), in men (hatched bar) and women (black bar), classified by age group, Dubbo Osteoporosis Epidemiology Study, Australia, 1989–1997.

 
For both of these types of fractures, a high clustering of fracture cases was observed among subjects with osteoporosis (21 percent in men, 43 percent in women) and osteopenia (47 and 52 percent, respectively), for example, by using femoral neck BMD. In women, no humerus fracture was observed in normal subjects. As a result, the incidence of fractures was highest among osteoporotic subjects, medium among osteopenic subjects, and lowest among normal subjects (figure 2). For both sexes, incidence also increased linearly with height loss (figure 3). In the previous 12 months, 47 percent of men and 63 percent of women with a fracture had had at least one fall, and the incidence of fractures was highest among those who had had multiple falls (figure 4).



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FIGURE 2. Incidence of humerus fractures (left panel) and of forearm and wrist fractures (right panel), expressed as fracture cases per 10,000 person-years (p-yrs), in men (hatched bar) and women (black bar), classified by femoral neck bone mineral density (FNBMD) category, Dubbo Osteoporosis Epidemiology Study, Australia, 1989–1997. Osteoporosis: men, <0.74 g/cm2 and women, <0.70 g/cm2; osteopenia: men, 0.74–0.92 g/cm2 and women, 0.70–0.88 g/cm2; and normal: men, >0.92 g/cm2 and women, >0.88 g/cm2.

 


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FIGURE 3. Incidence of humerus fractures (left panel) and of forearm and wrist fractures (right panel), expressed as fracture cases per 10,000 person-years (p-yrs), in men (hatched bar) and women (black bar), classified by height loss category, Dubbo Osteoporosis Epidemiology Study, Australia, 1989–1997.

 


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FIGURE 4. Incidence of humerus fractures (left panel) and of forearm and wrist fractures (right panel), expressed as fracture cases per 10,000 person-years (p-yrs), in men (hatched bar) and women (black bar), classified by fall category, Dubbo Osteoporosis Epidemiology Study, Australia, 1989–1997.

 
Baseline characteristics
Of the men, fracture subjects were generally older and had a significantly lower BMD (in terms of both actual measurement and age-and-weight-adjusted z score), muscle weakness (humerus fracture), a lower dietary calcium intake (forearm and wrist fractures), and a greater height loss compared with nonfracture subjects. Women who had had a fracture were also older, had a lower BMD in the femoral neck and lumbar spine, had a shorter stature, and had suffered a greater height loss compared with women who had not had a fracture.

In the two fracture groups, women with a humerus fracture were older and had a significantly lower BMD and weight than those with forearm and wrist fractures. As was true for women, men with humerus fractures were also older and had a lower BMD than those with forearm and wrist fractures (table 1).


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TABLE 1. Characteristics of study subjects classified by fracture status, Dubbo Osteoporosis Epidemiology Study, Australia, 1989–1997

 
Univariate analysis
Univariate analysis showed that age, femoral neck BMD, and height loss were common predictors of humerus, forearm, and wrist fractures in both men and women. For men, each 5 years of advancing age was associated with a 2.8- and 1.6-fold increase in humerus and in forearm and wrist fractures, respectively. For women, the age-fracture strength of association was weaker (relative risks: 1.6 for humerus and 1.3 for forearm and wrist fractures). Each 0.1 g/cm2 decrease in femoral neck BMD was associated with a 2.3- and 2.8-fold increase in humerus fracture in men and women, respectively. A similar reduction in femoral neck BMD was associated with a 1.8- and 1.5-fold increase in the risk of forearm and wrist fractures in men and women, respectively. Lumbar spine BMD was also a significant predictor of humerus fractures in men and women and of forearm fractures in women; however, the strength of the association was slightly weaker than that for femoral neck BMD.

Shorter current height was a significant risk factor for forearm and wrist fractures but not for humerus fracture. However, height loss (calculated as the difference between current height and peak height at age 30 years) was a common predictor of humerus, forearm, and wrist fractures in both men and women. Lower weight was a significant risk factor for humerus fracture in women but not in men.

Approximately 20 percent of men and 33 percent of women reported that they had fallen in the last 12 months before entering the study. Of these women, 22 percent had fallen once, as had 14 percent of men. About one third of both men and women who had fallen had done so multiple times (6 percent of men, 11 percent of women). History of falls was also a significant predictor of humerus fracture (in both men and women) and forearm and wrist fractures (in women only). While quadriceps weakness was a significant predictor of humerus fracture in men, body sway was a significant predictor of humerus fracture in women.

While the incidence of fractures in smokers was not significantly different from that in nonsmokers, alcohol drinkers had a significantly higher risk of humerus fracture than nondrinkers did. Lower dietary calcium intake was also a significant risk factor for forearm and wrist fractures in women but not in men (table 2).


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TABLE 2. Univariate analysis of risk factors for humerus, forearm, and wrist fractures in men and women, Dubbo Osteoporosis Epidemiology Study, Australia, 1989–1997

 
Multivariate analysis
When both backward and stepwise algorithms were used to consider all of these risk factors in a multivariate model, the following factors were identified as independent predictors of fracture risk: for humerus fracture, femoral neck BMD was a single predictor for men, while height loss was an additional independent factor for women; for forearm and wrist fractures, femoral neck BMD, height loss, and dietary calcium intake were independent predictors for men, and femoral neck BMD, height loss, and history of falls were independent predictors for women (table 3).


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TABLE 3. Multivariate analysis of independent risk factors for humerus, forearm, and wrist fractures in men and women in the Dubbo Osteoporosis Epidemiology Study, Australia, 1989–1997*

 
In a further analysis, femoral neck BMD was dichotomized into osteoporosis and nonosteoporosis; the relative risk was then estimated for the former category. For men, osteoporosis, with a prevalence of 10.8 percent, was associated with a 6.3-fold increase in humerus fracture risk; in women, the prevalence of osteoporosis was higher (27 percent), and these osteoporotic women had a 5.3-fold increase in fracture risk. For forearm and wrist fractures, the relative risks associated with osteoporosis were 5.7 for men and 2.1 for women (data not shown).


    DISCUSSION
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
While much research effort has been directed toward identifying risk factors for hip fractures in women, little is known about the etiology and pathophysiology of upper limb fractures, despite the fact that they are the third most common group of fractures in the elderly (8Go). The present longitudinal study showed that the risk of these fractures in women was three times higher than that in men; for both sexes, the risk increased exponentially with advancing age. The present study also identified three major groups of risk factors principally related to BMD, age, and falls. Since these risk factors are interrelated, this study found that for both men and women, femoral neck BMD and height loss were common and independent predictors. Moreover, specific risk factors such as low dietary calcium intake (in men) and falls (in women) were additional independent predictors of forearm and wrist fractures.

The finding that femoral neck BMD is one of the best predictors of humerus, forearm, and wrist fractures is consistent with a previous study of women (7Go). In fact, the strength of the association for women, assessed in terms of relative risk, was somewhat lower than that of hip fracture (20Go). Nevertheless, osteoporotic women (2.5 standard deviations below the young normal mean) had a 5.3- and 2.1-fold increase in the risk of humerus and of forearm and wrist fractures, respectively. The strength of the association was even higher for men: 6.3-fold for humerus and 5.6-fold for forearm and wrist fractures. Lumbar spine BMD was associated with fracture risk for both men and women; however, it was not independent of femoral neck BMD. This study did not measure forearm BMD, but the strength of the association between femoral neck BMD and fracture risk, as reported in this paper, is comparable to that reported in the literature (21Go), suggesting that the discriminatory power of measuring BMD in the femoral neck is equivalent to that in the forearm. These findings also suggest that low-trauma upper-limb fractures are largely osteoporotic.

For both sexes, a history of height loss was an independent and common predictor of fracture risk. Height loss has been found to be associated with hip fracture in men (22Go) and women (23Go). These results suggest that the greater height loss may reflect a more generalized state of bone loss or that height loss is a surrogate for vertebral deformity. Indeed, a study of 144 men found that vertebral deformity was associated with reduced vertebral and femoral neck BMD and that the number of vertebral deformities was negatively correlated with BMD (24Go). Vertebral deformity has also been associated with subsequent nonvertebral fractures independent of BMD (25Go).

Poor grip strength has also been noted as a risk factor for hip fracture (26Go). Since quadriceps weakness and postural instability are associated with falls (27Go), their role in predicting fracture implies that the event of fracture is not only a function of BMD but also a result of fall-related mechanisms. Apart from BMD and height loss, the present study also indicated that falls were strongly predictive of the risk of forearm and wrist fractures, particularly in women. Indeed, risk of fracture among fallers was almost threefold higher than that among nonfallers. Falls were reported by one in three women and increased with advancing age to 40 percent among women aged 80 years or more. Those who fell once had a higher risk of recurrent falls. These observations are similar to those of Prudham and Evans (28Go), who also found that falls were more common in women than in men (34 vs. 19 percent). Age, postural stability, and quadriceps strength were strongly associated with falls (27Go); thus, it was expected that higher body sway and quadriceps weakness would be associated with fractures. When falling was factored into the proportional hazards model, both quadriceps strength and body sway became statistically nonsignificant.

In this study sample, higher dietary calcium intake was associated with higher BMD in both the spine and the hip (10Go), in agreement with Kelly et al. (29Go). Also, dietary calcium intake was inversely related to age for men but not women. Thus, the finding that dietary calcium intake was an independent predictor of humerus fracture in men but not women may reflect other age-related factors, such as hyperparathyroidism, involved in the determination of the risk of fractures in men. It has been proposed that estrogen deficiency causes bone loss in women (both the early postmenopausal accelerated phase and the late postmenopausal slow phase) and elderly men. The loss of bone is associated with progressive secondary hyperparathyroidism, which may activate bone turnover and hence cause bone loss. The relation between bone loss and secondary hyperparathyroidism is mediated mainly by loss of estrogen action on extraskeletal calcium homeostasis, which results in net calcium wasting and in increases in the level of dietary calcium intake required to maintain bone balance. Recent data (30Go) indicated that estrogen is at least as important as testosterone in determining bone mass in men. In addition, elderly men have low circulating levels of both bioavailable estrogen and bioavailable testosterone; thus, estrogen deficiency may also contribute substantially to the continuous bone loss and hence increase the risk of fracture in men.

The role of lifestyle factors as determinants of BMD and hence fracture risk has received considerable attention. Smoking has been implicated as a risk factor for spinal fracture in men (31Go) and in women (31Go). In the present study, despite smoking being negatively associated with BMD (12Go), which is consistent with findings from several cross-sectional studies of women (33GoGo–35Go), this relation did not translate to a higher risk of fracture. Higher physical activity had a protective effect against fracture risk, consistent with previous observations regarding hip fractures, as reported by Lau et al. (36Go) for Chinese men and by Cooper et al. (26Go) for a British population. However, in the present study, the association between physical activity and fracture risk was not independent of femoral neck BMD.

Fractures of the humerus and forearm are a risk factor for subsequent hip fracture (37Go, 38Go). In fact, it has been estimated that as many as 16 percent of women with hip fractures have had a previous distal radial fracture (39Go). Findings from the present study tend to indicate that the relation between upper-limb and hip fractures in persons who fall, compared with the general population, may be mediated by their greater propensity to fall and to be characterized by more-severe osteoporosis.

The present findings should be interpreted conditional on a number of potential limitations. The study population was of Caucasian background; therefore, generalization may not be applicable to other racial populations. Measurements of postural sway, BMD, dietary calcium intake, and physical activity index at a single time point included three measurement errors and hence could have underestimated any true association between these factors and fracture risk. It is possible that selection bias was present in the analysis, in that subjects who participated in the study were healthier than those who did not. Center et al. observed that mortality was generally lower in the present study sample compared with the overall community (40Go). Finally, epidemiologic data on factors directly affecting hip fracture risk cannot be taken as definitive evidence of causal associations.

This study has important implications for the prevention of upper-limb fractures. More than 40 percent of the humerus, forearm, and wrist fractures occurred in men and women whose femoral neck BMD was less than 0.7 g/cm2 (the cutoff level for the definition of osteoporosis). This severity of osteoporosis occurred in 11 percent of the men and 27 percent of the women. A history of falls also emerged as an important risk factor. Taken together, these data indicate that screening strategies that focus on persons with low BMD and a high risk of falling are likely to be more effective than focusing on low BMD alone. Interventions directed at reducing falls might be effective in reducing the incidence of forearm and wrist fractures, particularly in the elderly whose BMD is already below the fracture threshold.

In summary, femoral neck BMD, falls, and height loss or dietary calcium intake are independent risk factors for humerus, forearm, and wrist fractures in community-dwelling men and women. It seems that measures to maintain BMD and prevent falls, adequate exercise, and dietary calcium intake could contribute to a reduction in the incidence of upper-limb fractures in elderly men and women.


    ACKNOWLEDGMENTS
 
This work was supported by the Australian Institute of Health, the Australian Dairy Corporation, and the LUNAR Corporation and is supported by the National Health and Medical Research Council of Australia.

The authors acknowledge the expert assistance of Janet Watters and Angela Ferguson in conducting interviews, collecting the data, and measuring bone densitometry and of Orana Radiology Services in conducting radiologic analyses. The authors also acknowledge the invaluable help of the Dubbo Base Hospital staff, particularly B. Luton, M. Russell, and B. Ayrton.


    NOTES
 
Correspondence to Dr. Tuan V. Nguyen, The Simpson Centre, University of New South Wales, Liverpool Hospital, Locked Bag 7103, Liverpool BC NSW 1871, Australia (e-mail: t.v.nguyen{at}unsw.edu.au).


    REFERENCES
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Riggs BL, Melton LJ III. Involution osteoporosis. N Engl J Med 1986;314:1676–86.[ISI][Medline]
  2. Cummings SR, Kelsey JL, Nevitt MC, et al. Epidemiology of osteoporosis and osteoporotic fractures. Epidemiol Rev 1985;7:178–208.[ISI][Medline]
  3. Randell A, Sambrook PN, Nguyen TV, et al. Direct clinical and welfare costs of osteoporotic fractures in elderly men and women. Osteoporos Int 1995;6:427–37.
  4. Nilsson BE, Westlin NE. The bone mineral content in the forearm of women with Colles' fracture. Acta Orthop Scand 1974;45:836–44.[ISI][Medline]
  5. Eastell R, Wahner HW, O'Fallon WM, et al. Unequal decrease in bone density of lumbar spine and ultradistal radius in Colles' and vertebral fracture syndromes. J Clin Invest 1989;83:168–74.[ISI][Medline]
  6. Hesp R, Klenerman L, Page L. Decreased radial bone mass in Colles' fracture. Acta Orthop Scand 1984;55:573–5.[ISI][Medline]
  7. Kelsey JL, Browner WS, Seeley DG, et al. Risk factors for fractures of the distal forearm and proximal humerus. Am J Epidemiol 1992;135:477–89.[Abstract]
  8. Jones G, Nguyen T, Sambrook PN, et al. Symptomatic fracture incidence in elderly men and women: the Dubbo Osteoporosis Epidemiology Study. Osteoporos Int 1994;4:277–82.[ISI][Medline]
  9. Nguyen T, Sambrook P, Kelly P, et al. Prediction of osteoporotic fractures by postural instability and bone density. BMJ 1993;307:1111–15.[ISI][Medline]
  10. Nguyen TV, Kelly PJ, Sambrook PN, et al. Life-style factors and bone density in the elderly: implications for osteoporosis prevention. J Bone Miner Res 1994;9:1339–46.[ISI][Medline]
  11. Jones G, Nguyen TV, Sambrook PN, et al. Progressive femoral neck bone loss in the elderly: longitudinal findings from the Dubbo Osteoporosis Epidemiology Study. BMJ 1994;309:691–5.[Abstract/Free Full Text]
  12. Angus RM, Sambrook PN, Pocock NA, et al. A simple method for assessing calcium intake in Caucasian women. J Am Diet Assoc 1989;89:209–14.[ISI][Medline]
  13. Kannel WB, Sorlie PD. Some health benefits of physical activity: the Framingham study. Arch Intern Med 1979;139:857–61.[ISI][Medline]
  14. Lord SR, Clarke RD, Webster IW. Postural stability and associated physiological factors in a population of aged persons. J Gerontol 1991;46:M57–66.[ISI][Medline]
  15. Nguyen TV, Sambrook PN, Eisman JA. Sources of variability in bone mineral density measurements: implications for study design and analysis of bone loss. J Bone Miner Res 1997;12:125–35.[ISI]
  16. Cox DR. Regression models and life tables (with discussion). J R Stat Soc (B) 1972;34:187–220.[ISI]
  17. SAS Institute, Inc. SAS/STAT software: changes and enhancements, release 6.07 ed. Cary, NC: SAS Institute, Inc, 1992:443–80. (SAS technical report P-229).
  18. Lee ET. Statistical models for survival data analysis. Belmont, CA: Lifetime Learning Publications, 1980.
  19. SAS Institute, Inc. SAS/STAT user's guide, release 6.03 ed. Cary, NC: SAS Institute, Inc, 1990:549–640.
  20. Cummings SR, Black DM, Nevitt MC, et al. Bone density at various sites for prediction of hip fractures. Lancet 1993;341:72–5.[ISI][Medline]
  21. Gardsell P, Johnell O, Nilsson BE. Predicting fractures in women by using forearm bone densitometry. Calcif Tissue Int 1989;44:235–42.[ISI][Medline]
  22. Center JR, Nguyen TV, Pocock NA, et al. Femoral neck axis length, height loss and risk of hip fracture in males and females. Osteoporos Int 1998;8:75–81.[ISI][Medline]
  23. Gunnes M, Lehmann EH, Mellstrom D, et al. The relationship between anthropometric measurements and fractures in women. Bone 1996;19:407–13.[ISI][Medline]
  24. Jones G, Nguyen T, Sambrook PN, et al. A longitudinal study of the effect of spinal degenerative disease on bone density in the elderly. J Rheumatol 1995;22:932–6.[ISI][Medline]
  25. Ross PD, Davis JW, Epstein RS, et al. Pre-existing fractures and bone mass predict vertebral fracture incidence in women. Ann Intern Med 1991;114:919–23.[ISI][Medline]
  26. Cooper C, Barker DJ, Wickham C. Physical activity, muscle strength, and calcium intake in fracture of the proximal femur in Britain. BMJ 1988;297:1443–6.[ISI][Medline]
  27. Lord S, Sambrook PN, Nguyen TV, et al. Postural stability and falls in the elderly population. Med J Aust 1994;160:684–91.[ISI][Medline]
  28. Prudham D, Evans JG. Factors associated with falls in the elderly: a community study. Age Ageing 1981;10:141–6.[Abstract]
  29. Kelly PJ, Pocock NA, Sambrook PN, et al. Dietary calcium, sex hormones and bone mineral density in normal men. BMJ 1990;300:1361–4.[ISI][Medline]
  30. Center JR, Nguyen TV, Sambrook PN, et al. Hormonal and biochemical parameters and osteoporotic fractures in elderly men. J Bone Miner Res 2000;15:1405–11.[ISI][Medline]
  31. Seeman E, Melton LJ III, O'Fallon WM, et al. Risk factors for osteoporosis in males. Am J Med 1983;75:977–82.[ISI][Medline]
  32. Hemenway D, Colditz GA, Willet WC, et al. Fractures and lifestyle: effect of cigarette smoking, alcohol intake, and relative weight on the risk of hip and forearm fractures in middle-aged women. Am J Public Health 1988;78:1554–8.[Abstract]
  33. Slemenda CW, Hui SL, Longcope C, et al. Cigarette smoking, obesity and bone mass. J Bone Miner Res 1989;4:737–41.[ISI][Medline]
  34. Daniel HW. Osteoporosis of the slender smokers. Arch Intern Med 1976;136:298–304.[Abstract]
  35. Pocock NA, Eisman JA, Kelly PJ, et al. Effects of tobacco use on axial and appendicular bone mineral density. Bone 1989;10:329–31.[ISI][Medline]
  36. Lau E, Donnan S, Barker DJP, et al. Physical activity and calcium intake in fracture of the proximal femur in Hong Kong. BMJ 1988;297:1441–3.[ISI][Medline]
  37. Lauritzen JB, Schwarz P, McNair P, et al. Radial and humerus fractures as predictors of subsequent hip, radial or humerus fractures in women and their seasonal variation. Osteoporos Int 1993;3:133–7.[ISI][Medline]
  38. Gay JD. Radial fracture as an indicator of osteoporosis: a 10-year follow-up study. Can Med Assoc J 1974;111:156–7.[Medline]
  39. Alffram PA. An epidemiological study of cervical and trochanteric fractures of the femur in an urban population. Acta Orthop Scand 1964;suppl 65:1–109.
  40. Center JR, Nguyen TV, Schneider D, et al. Mortality after all major types of osteoporotic fracture in men and women: an observational study. Lancet 1999;353:878–82.[ISI][Medline]
Received for publication August 30, 1999. Accepted for publication June 22, 2000.