Garvan Institute for Medical Research, St Vincent's Hospital, NSW, Australia. Abstract. This longitudinal population-based study documents the incidence of all ...
Osteoporosis Int (1994) 4:277-282 © 1994European Foundation for Osteoporosis
Osteoporosis International
Original Article Symptomatic Fracture Incidence in Elderly Men and Women: The Dubbo Osteoporosis Epidemiology Study (DOES) G. Jones, T. Nguyen, P. N. S a m b r o o k , P. J. Kelly, C. Gilbert and J. A. Eisman Garvan Institute for MedicalResearch, St Vincent's Hospital, NSW, Australia
Abstract. This longitudinal population-based study documents the incidence of all symptomatic fractures from 1989 to 1992 in an elderly, predominantly Caucasian population of males and females (I>60 years as at 1 January 1989) living in the geographically isolated region of the city of Dubbo, NSW, Australia. Fractures were ascertained by reviewing reports from all radiology services in the region. There were 306 fractures in 271 patients during the study period representing 11 401 person-years of observation. In the 60-80 year age group only 10% of fractures involved the hip, while in the over-80 age group this proportion rose to 41%. Incidence of distal forearm, hip and total fractures increased exponentially in both sexes with increasing age. Rib fractures were relatively common, with incidence rates for rib fractures similar to those for humeral fractures. Overall fracture incidence was 2685 per 100000 person-years (males 1940 per 100000 and females 3250 per 100000). Residual lifetime fracture risk in a person aged 60 years with average life expectancy was 29% for males and 56% for females. Symptomatic fracture rates with the improved methodology in this study were higher than previously reported in both elderly males and females, with a marked preponderance of non-hip fractures in the 60-80 year age group. These symptomatic fractures have previously been underestimated, if not largely ignored, in public health approaches including cost-benefit analyses of osteoporosis prevention and treatment. Total fracture risk during later life is substantial, with fractures other than Correspondence and offprint requests to: Associate Professor P. N. Sambrook, Bone and MineralResearchDivision,GarvanInstitute for Medical Research, St Vincent's Hospital, 384 Victoria St, Darlinghurst, NSW, Australia 2010.
hip fractures constituting the majority of morbid fracture events, especially in the 60-80 year age group.
Keywords: Elderly; Epidemiology; Fracture; Incidence; Osteoporosis
Introduction Osteoporosis, with its sequelae of fracture, is a major public health problem, especially in contemporary Western society with its aging population. These fractures generally increase exponentially in incidence with age [1,2]. Most studies have concentrated almost exclusively on osteoporotic fractures in women. With increasing longevity in males, osteoporosis will become of increasing importance in both males and females. The cost of osteoporotic fractures includes medical costs directly related to fracture treatment and indirect costs. The total cost of osteoporosis is unknown but has been estimated in the United States to be SUS 5.15 billion in 1986 [3]. Reliable estimates of total cost are lacking in other countries. While hip fracture is a major component of cost associated with osteoporosis it is not the only contribution to costs and represented only 38% of total costs in the United States [3]. Projections for future health planning require reliable estimates of fracture incidence, especially in the elderly. The aims of this study were twofold: firstly, to provide data documenting the incidence of all symptomatic fractures (i.e. those presenting for radiography) in a population-based study of an elderly, predominantly Caucasian, male population and, secondly, to assess incidence in a comparable elderly female population.
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Methods The city of Dubbo has a population of approximately 32000 and is situated 400 km north-west of Sydney, Australia. This community included approximately 1600 men and 2100 women aged 60 years or over (as at 1 January 1989) who were 98.6% Caucasian (see Table 3 for the age and sex breakdown of the midterm population). The methods of identifying this population are described in detail elsewhere [4]. The population is ideally suited to epidemiological research being relatively isolated with its own centralized health services. The D u b b o Osteoporosis Epidemiology Study ( D O E S ) commenced in 1989. Its aims were to describe fracture incidence, risk factors and economic costs associated with fractures in a cohort of representative elderly Australians. This present study examined fracture incidence in the whole population aged 60 years and over (identified in 1989). Fractures were identified through radiologists' reports from the only two centres in the region providing radiology services. Fractures were included if there was a definite report of fracture and the patient's normal place of residence was in Dubbo local government area (postcode 2830 or 2831). Fractures clearly due to major trauma, such as motor vehicle accidents, were not included but those due to minor trauma were. Circumstances surrounding the fracture event were determined by personal interview after the fracture (within 1 month for all subjects). Proxies were sought where the history was uncertain. Possible or probable fracture reports were excluded. Atraumatic fractures were defined as those that occurred with a fall from standing height or less [2]. Vertebral fractures were regarded as incident only if there was a recent clinical history suggestive of fracture
and/or a radiograph within the previous 2 years which did not show a fracture. Radiologists' reports were examined independently by two of the authors (G.J. and T.N.) to ensure agreement in identifying fracture cases correctly. The study period reported here was from July 1989 to September 1992.
Statistical Methods Statistics were descriptive with age, sex and type of fracture. The midterm population, which was used for calculating fracture incidence rates, was calculated by identifying the population at the beginning of the study and monitoring deaths in the geographic area of the study during the study period. The population of Dubbo is stable and it was assumed that net migration in this elderly cohort was zero. Estimates of total numbers of Australian fractures were calculated using 1992 Australian data on the population over 60 years of age (supplied by the Australian Bureau of Statistics).
Results There was a total of 306 fractures in 271 individuals in the 3.25-year study period. Thirteen subjects sustained multiple fractures (total 34) at different times during the study period. The maximum sustained by any one individual was five (humerus, wrist, hand, hip and ankle). Twelve subjects sustained a total of 26 atraumatic fractures from the one event. The maximum sustained by two individuals was three fractures (interestingly, distal forearm, hip and pelvis in both cases). This represented 11401 person-years of observation amongst the population of 3508 at risk. Total fractures
Table 1. Total fracture incidence by sex and type Site
Number
Incidence (per 100 000 person-years at risk) Male
Skull and facial Upper limb Clavicle Humerus Distal forearm Other forearm Carpus Hand Ribs Vertebral Pelvis Lower limb Hip Other femur Patella Leg Ankle Foot Total
6 34 52 5 1 10
58 8 6 13 25 19
5 108
Female 41 632
41 244 244 0 0 61 36 15 13 129
46 1186 60 339 617 77 15 108
366 81 41 893 244 8I 21 81 264 122
306
Total
53 311 456 44 8 87 277 169 169 1309
709 62 77 139 185 200 1940
44 948
315 132 114 1132 509 70 52 114 219 167
3250
2685
Symptomatic Fracture Incidence in the Elderly (DOES)
279
10000
10000-
Male
~g
Female
8000
8000
6o00
6000
Total
Non-hip Total
&
=
4000
4000-
Hip
Non-hip Hip
2000
Distal forearm
2000Distal forearm
0
0
60-64
65-69
70-74
75-79
80+
tr~ .
.
60-64
.
.
65-69
Age (years)
70-74
.
"
75-79
80+
Age (years)
F i g . 1. Age-specific fracture incidence for males and females. There is an exponential increase in total and hip fracture for both sexes with increasing age. There is also an exponential increase in non-hip and distal forearm fractures in females but not males. Non-hip fractures, which included distal forearm fractures, were considerably more common than hip fractures in all age groups. In the 60-80 year age group, only 10% of fractures involved the hip while in the over-80 age group this proportion rose to 40%.
Table 2. Age- and sex-specific incidence rates for hip fractures in Caucasian populations (per 100 000 person-years) Area and period of study
Presend study 1989-92 NSW, Australia 1989-90 [12] Rochester, USA 1%5-74 [6] California, USA 1983-84 [7] New Zealand, 1973-76 [8] Central Norway t983-84 [9] Southampton, UK 1986 [10] Yorkshire, UK 1973-77 [11]
Men, age (yr)
Women, age (yr)
60-69
70-79
80+
60-69
70-79
80+
68 62 92 90 51 346 44 51
243 242 192 334 t86 867 100 140
2031 954 1281 1209 862 3234 402 548
174 118 250 213 122 5t3 56 104
509 570 674 726 494 1611 296 371
3948 2126 2108 2502 1988 5689 1388 1200
had an incidence of 2685 per 100 000 person-years. The most common fractures were distal forearm, humerus, hip, ribs and ankle. Seventy-four patients with vertebral fractures were identified but only 15 of these were considered new fractures using our strict criteria. The overall fracture incidence in females was 3250 per 100 000 person-years and in males was 1940 per 100 000 person-years. The total number of fractures, according to site and incidence by sex, are shown in Table 1.
Twenty fractures amongst 13 patients were classified as due to minor trauma possibly exceeding that of a fall from standing height, e.g. an ankle fracture due to falling off a crate. Fifteen fractures in 12 patients were considered secondary to malignancy or bone disease other than osteoporosis. The remaining 271 fractures were atraumatic. Table 2 and Fig. 1 relate to atraumatic fractures only. Fracture incidence for total, non-hip, hip and distal
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G. Jones et al. Table 3. Age-specificincidence of fractures from the Dubbo Osteoporosis Epidemiology Study (DOES) and estimated incidence of total fractures in Australia 1992 Age group (yr) 6(~4
65-69
70-74
75-79
80+
Total
16 384 12.8 325.3 4164
15 308 15.0 239.1 3587
23 198 35.7 161.8 5776
17 106 49.3 134.8 6646
95 1508 19.4 1223.5 23930
43 477 27.7 351.2 9728
26 414 19.3 291.9 5634
40 311 39.6 227.9 9025
65 214 93,5 258,7 24188
211 2000 32.5 1495.0 48590
Males
Fracturesa 21 Midterm Dubbo population 512 Rate per 1000 population per year 12.6 Australian pop. 1992 (thousands) 362.5 Estimated fractures in Australia 4568 Females
Fracturesa 34 Midterm Dubbo population 584 Rate per 1000 population per year 17.9 Australian pop. 1992 (thousands) 365.2 Estimated fractures in Australia 6537
aThe incidence of fractures reported here excluded 6 fractures in 5 subjects (3 male, 2 female) whose exact age (although greater than 60 years) was not known but which are included in the total. forearm fracture by age group and sex is shown in Fig. 1. In the 60.80 year age group, only 11% of total fractures involved the hip. This proportion rose to 41% in the over-80 age group but this group made up only 9% of the elderly population. These proportions were the same for males and females. Age-specific incidence for males and females showed a marked increase in both sexes with age, most marked after age 70.74 years. There was no clear pattern of seasonal variation in total fractures for the 3-year period from 1 January 1989 to 30 September 1992. A comparison of hip fracture incidence by age and sex in our study with other studies describing fracture incidence in Caucasian populations is shown in Table 2. Estimates of the number of fractures that would have occurred in the Australian population in 1992 if our data are applied to the whole population are shown in Table 3. At age 60 years, average life expectancy in Australia is 19 years for males and 23 years for females (supplied by the Australian Bureau of Statistics). Accordingly, in this Caucasian population, a person aged 60 years with average life expectancy would have a residual lifetime risk of an atraumatic fracture event of 29% in males and 56% in females.
Discussion This paper details the first comprehensive description of total symptomatic fracture incidence in both males and females in an elderly population. There was an exponential increase in most fractures with age. Although comparison of incidence rates between studies is somewhat limited by differences in fracture ascertainment in different study populations, overall fracture rates were generally higher than most previously reported studies for total, hip and distal forearm
fractures. With regard to hip fracture, the age- and sexspecific incidence rates from our study are comparable with those reported in other studies and a cross-national analysis [5]. In comparison with other Caucasian populations, hip fracture incidence was average in the 60-69 and 70-79 year age groups for both males and females but second highest after central Norway in the 80+ age group [6-11]. This trend was also evident when compared with previous Australian estimates of hip fracture incidence [12], in which hip fracture cases were identified by hospital discharge coding which may underestimate fracture incidence (see below). Moreover, our study shows that non-hip fractures constitute the majority of fractures, particularly in the 60-80 year age group. As the Dubbo population is representative of elderly Australians in terms of recognized fracture risk factors such as sociodemographic variables (including the proportion institutionalized), tobacco and alcohol usage, prescribed medication, weight, height and overall health status [13], our extrapolation to the whole Australian population greater than 60 years of age provides a valid estimate of the total annual symptomatic fracture rate in elderly Australians. On the basis of previous cost estimates for osteoporosis [3,14], this indicates an accompanying annual cost of $A 300 million or $18 ($ US12) for every man, woman and child. Most previous studies have examined fractures at specific skeletal sites and there have been few epidemiological studies examining total fractures. A recent population-based study in Leicestershire, U K [15] reported annual age- and sex-specific incidence rates which were considerably lower than those found in this study and direct comparison of individual fractures indicates this difference was evident at most fracture sites, suggesting a true difference rather than changes in case ascertainment, which would be expected to miss some but not hip fractures. Site-specific incidence rates in our study revealed some interesting trends. Most previous studies
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of distal forearm fractures have found these to be the most common fracture from age 50 to 75 years, after which hip fractures become more common [2]. The incidence rate for distal forearm fractures we observed was lower that that found in the United States in women aged
