REMARKABLE DECLINE IN HIP FRACTURE INCIDENCE IN YOUNGER AGE GROUPS IN GERMANY

Hip fractures have a large economic impact because of the requirement of hospital and follow-up care, in addition to causing substantial health deterioration.1 Numerous studies have presented trends of hip fracture incidence, focusing on people aged 45 or 50 years and older.2^,3 Data on younger age groups has not been discussed yet. Analyses of trends for injury-related hospitalization do not separately report hip fractures3^–5 as do analyses of other injuries (e.g., traumatic brain injury).6 The majority of hip fractures occur in older age groups because of low mineral bone mass, which leads to an increased risk of fall-related fractures. However, a substantial proportion of hip fractures occur among people younger than 40 years old, particularly men. For example, in Germany in 1995, 10% of all persons suffering a hip fracture were men younger than 40 years old.

We analyzed the trend of hip fracture incidence in Germany using the national register of hospital discharges from 1995 to 2004. The register has been proven for completeness and validity.7 We standardized incidences to the 2000 German population and estimated age- and gender-adjusted incidence rate ratios (IRRs) using multiple Poisson regression with correction for overdispersion. Overall, hip fracture incidence increased slightly but was statistically significant (IRR=1.05; 95% confidence interval=1.02, 1.07). The trend in adults younger than 40 years old was striking. The incidence of hip fractures (per 100000 person years, corrected for recurrent admissions) declined from 8.5 in 1995 to 6.1 in 2004 among men, and from 3.8 to 2.2 among women. The IRRs are shown in the Table 1 ▶.

TABLE 1—

Hip Fracture Incidence Rates and Incidence Rate Ratios (IRRs) in Persons Younger Than 40 Years Old: Germany, 1995–2004

	Incidence Rates per 100 000a
	1995	1996	1997	1998	1999	2000	2001	2002	2003	2004	Average annual IRR	IRR (95% CI)b
Male
Age, y
0–9	3.7	2.7	2.2	2.4	1.7	2.2	1.9	2.1	1.9	1.5	0.93*	0.51 (0.39, 0.66)*
10–19	6.4	6.8	5.9	5.8	5.1	5.7	4.7	4.9	4.8	4.7	0.96*	0.69 (0.60, 0.80)*
20–29	8.6	7.7	6.7	6.0	6.0	6.3	5.1	5.9	5.9	5.4	0.95*	0.65 (0.57, 0.75)*
30–39	12.5	12.0	11.8	10.9	10.3	10.5	9.8	10.7	11.2	10.1	0.98*	0.84 (0.75, 0.93)*
Female
Age, y
0–9	3.2	2.1	1.9	1.8	1.7	2.0	1.4	1.3	1.4	1.1	0.91*	0.41 (0.31, 0.55)*
10–19	3.8	2.8	2.7	2.2	2.0	2.1	1.8	2.1	2.1	1.8	0.93*	0.53 (0.41, 0.67)*
20–29	2.7	2.2	2.2	2.2	2.1	2.2	1.6	1.3	1.7	1.5	0.94*	0.57 (0.44, 0.74)*
30–39	4.9	4.0	4.0	3.7	3.2	3.8	3.2	3.4	3.5	3.7	0.97*	0.76 (0.66, 0.88)*

Note. CI = confidence interval. Incidences were standardized to the 2000 German population.

^aEstimated from the number of hospital discharges and corrected for double registration and recurrent admissions (correction factor = 0.68).7

^bEstimated from the average annual IRR from 1995 to 2004. We estimated age- and gender-adjusted IRRs using multiple Poisson regression with correction for overdispersion.

* P < .01.

There are several explanations for the declines in incidence. In Germany, as well as in several other industrialized countries, the number of work-related accidents has declined continuously.8 The proportion of manual laborers has decreased, and safety programs have improved. Additionally, the number of traffic accidents with severe injury has decreased,8 owing to improved safety features in cars (e.g., airbags, safety belts) that may have contributed to the prevention of severe fractures when accidents occur. Data from the Centers for Disease Control and Prevention indicate a decline of injury-related hospitalizations in the United States during the past decades, in particular in younger age groups.5^,9 A shift from in-patient care to ambulatory care has been discussed as one possible reason for such a decline; however, hip fracture treatment generally requires hospital admission. Thus, the decrease in hip fracture-related hospitalization is likely to reflect a real decrease in hip fracture events.

Future epidemiological studies should carefully monitor hip fracture incidence trends in all age groups. Research is needed to clarify the reasons for the hip fracture decline in younger age groups.