Burden of Hip Fracture in Iran

Abstract

To measure the burden caused by hip fracture in Iran and to compare it with other parts of the world, we applied the Global Burden of Disease (GBD) method created by the World Health Organization. The GBD method uses disability-adjusted life years (DALY), which is comprised of years of life lost (YLL) and years of life lived with disability (YLD). To calculate YLD, incidence of hip fracture was obtained from the Iranian Multicenter Study on Accidental Injuries, a large-scale nationwide prospective study. Disability weights were applied to the remaining duration of disease. To calculate YLL, remaining years of potential life at any age at death were calculated using the standard life table. A discount rate of 3% and age weighting were applied. Hip fracture generated 16,708 DALYs, comprising 8,812 (52.7%) YLL and 7,896 (47.3%) YLD. Iran accounted for 0.85% of the global burden of hip fracture and 12.4% of the burden of hip fracture in the Middle East. The female to male ratio in Iran (1.1) was lower than the global (2.2) and the Middle Eastern (1.4) ratios and higher than the ratios in China and India (1.0 and 0.9, respectively). In conclusion, hip fracture is not as much a cause of disease burden in Iran as in the developed regions of the world. We recommend utilization of the standardized GBD method to calculate burden of osteoporosis in different countries and to set local priorities according to these measures.

Appendix

To calculate the number of deaths associated with hip fracture, the following template was applied. As an example, for females at the age of 52, estimated number of deaths among current 52-year-old women experiencing hip fracture this year was summed with the number of deaths of those experiencing hip fracture last year at the age of 51 dying 1 year after fracture and those experiencing hip fracture 2 years ago at the age of 50 dying 2 years after fracture. The appropriate age- and sex-specific mortality rates for each year following fracture were applied to the number of incident hip fractures in Iran for that age and sex after subtracting the estimated number of deaths of the previous years. The proportional excess death after hip fracture (compared to the general population of Sweden) was applied to the mortality rate of the Iranian general population to attain an estimate of the Iranian mortality rate after hip fracture for each age and sex [12, 15]. It was assumed that the proportional excess mortality in Iran was similar to that of Sweden (for each age and sex it was assumed that hip fracture mortality/mortality of the general population for Iran = hip fracture mortality/mortality of the general population for Sweden). For instance, the mortality rate for Iranian patients at the age of 52, two years after a hip fracture was calculated as d = (c/a) * b, as depicted in Figure 1.

Fig. 1.

Mortality rates (per 1,000) for years after hip fracture and of the general population of Iran and Sweden.

To calculate the number of deaths after hip fracture, the age and sex specific mortality rate for each year following fracture was applied to the estimated number of incident hip fractures for that age and sex after subtracting the estimated number of deaths of the previous year (Fig. 2).

Fig. 2.

Mortality rates (per 1,000) for the years following a hip fracture occurring at ages 50, 51, and 52 years and the general population.

The following template was used to calculate the number of deaths for all ages and continued until the maximum expected life expectancy.

  Number of hip fractures at age (N) = population at age i * incidence of hip fracture at age