Mortality and cause of death in hip fracture patients aged 65 or older - a population-based study

Hip fracture is the most serious consequence of falling in older people with osteoporosis; 87% to 96% of hip fracture patients are 65 years of age or older [1, 2]. Hip fractures are associated with increased mortality rates; the magnitude of the increased mortality and the length of its duration, however, are unclear. One study stated that survival declines soon after hip fracture, but thereafter parallels the expected survival of the general population [3]. A recent systematic epidemiologic review, however, showed that patients are at increased risk for premature death for many years after hip fracture [4].

Excess mortality after hip fracture may be linked to complications following the fracture, such as pulmonary embolism [5], infections [2, 6], and heart failure [2, 6]. Factors associated with the risk of falling and sustaining osteoporotic fractures may also be responsible for the excess mortality [1, 7]. Excess mortality after fracture may be due to the individual characteristics of the person sustaining the hip fracture [8]; e.g., low-bone density is associated with increased non-trauma mortality, even without fractures. Despite numerous mortality studies, further analysis of mortality and cause of death is important to identify the risk factors for death following trauma and to anticipate complications [9].

Although several studies report excess mortality in hip fracture patients compared to controls [1] the issue remains under-recognized in many countries. Furthermore, sex- and cause-specific mortality after hip fracture has not been extensively investigated [6]. The aims of the present population-based study were to evaluate patterns of death by sex and hip fracture type and to evaluate mortality after hip fracture compared to the general population with a specific focus on the cause of death.

The data analyzed in the present study were extracted from the records of hip fracture patients collected on a population-basis in the province of Satakunta in the western coastal region of Finland and from statistics on the general population collected on a cohort-basis of all persons 65 of age or older living in Finland. The referral area for hip fracture patients was the Satakunta Hospital District, which has a population of 235,580 (December 31, 1999). The number of residents 65 years of age or older in this district totalled 39,910 at the time of the study (16.9% of the population). Population figures for the hospital district and the entire country on December 31 in 1998 and in 1999 were obtained from the Official Statistics of Finland [10].

The present population-based study showed that during a 9-year follow-up, the age- and sex-standardized all-cause mortality of hip fracture patients was 3-fold higher than that of the general population. The increased mortality was related to every cause-of-death category, i.e., malignant neoplasm; dementia; diseases of circulatory, respiratory, and digestive systems; and other. Our study area lies in the western coast of Finland; there are regional differences of mortality in favor of Western Finland compared to Eastern Finland [12]. This aspect enhances the mortality difference between the hip fracture patients and the general population of our study. Of hip fracture patients, men had significantly higher mortality than women during the follow-up. Men were more likely to die from respiratory system disease, malignant neoplasms, and circulatory system disease after hip fracture than women. Sex differences in cause of death after hip fracture have not been systematically studied [6]. To our knowledge, there are no studies of mortality after hip fracture surgery with follow-up periods of several years in which cause of death was analyzed in association with sex.

In the present study, the increased age-adjusted mortality in men compared to women was obvious immediately after the hip fracture operation and persisted until the end of the follow-up, which is consistent with previous studies [6, 13, 14]. The reasons for the sex differences are unclear, although men tend to be sicker and frailer than women at the time of fracture [15]. Greater impairments in activities of daily living, mobility, and walking speed have been observed in male hip fracture patients compared to women. This may indicate a greater loss of physiologic reserve after hip fracture in men than in women and, hence, a greater risk of death [14].

This study revealed differences between sexes in cause of death after hip fracture. Men in our study were more likely than women to die from respiratory diseases. At baseline, respiratory diseases were more common in men than in women. Patient's history of smoking was not systematically recorded in the original patient records, and no data on smoking were collected. In Finland, however, smoking is more common in elderly men than in elderly women [16]. One explanation for the excess male mortality is the assumption that men are more prone to exacerbation of respiratory problems after hip fracture surgery (decreased secretion in the airways, impaired activities of daily living, and subsequent chest complications). In addition, smoking may be related to another finding of our study. Malignant neoplasms were more likely the cause of death for men than for women. A recent cancer survey in Europe concluded that differences in cancer mortality between sexes and European countries may be explained by smoking habits [17].

Some previous studies indicate that patients with heart disease may be more likely to fall and thus sustain a hip fracture as a consequence of impaired circulation, but impaired circulation may also increase the likelihood of dying after having sustained a fracture [1, 15]. Similarly, patients who are immobilized and those with osteoporosis following a stroke may not only have an increased risk of falls and fractures, but also an increased risk of dying following complications related to neurovascular disease [18]. The reason for the greater risk of death from circulatory disease in men after hip fracture cannot be addressed on the basis of the present study. In Finland, coronary heart diseases were previously very common in middle-aged men, but the occurrence has decreased over the past 10 to 20 years. In women, these diseases usually occur at an older age than in men [19]. Hence, circulatory system disease might be more severe and more long-term in older men than in older women.

Findings from analyses by fracture type showed no differences between cervical and trochanteric fracture patients in mortality or cause of death. In contrast, a Greek study of 499 hip fracture patients with trochanteric fracture predominance (67%) reported higher mortality after trochanteric hip fracture than after cervical hip fracture at 5 and 10 years after the incident [20]. Their conclusion was that the type of hip fracture was an independent predictor of long-term mortality in hip fracture patients. A Danish study of 2674 hip fracture patients with cervical hip fracture predominance (64%), however, reported that the mortality rates between cervical and pertrochanteric hip fracture patients were not significantly different during a mean follow-up of 2.6 years [21].

Rehabilitation of older patients falls under the purview of primary health care; geriatric rehabilitation is poorly established in Finland. After surgery, hip fracture patients are usually referred to local hospital wards for primary care, where the treatment is conservative with no special knowledge of modern geriatrics. A Finnish randomized, controlled intervention study of patients 65 years of age or older sustaining hip fracture showed that active rehabilitation performed by a geriatric team shortened the total hospital stay after a hip fracture operation and enhanced the recovery of daily activities [22]. The lack of a geriatric rehabilitation center in the Satakunta area may be one explanation for the high mortality of hip fracture patients of our report.

The accuracy of registering severe injuries like hip fractures is generally good in Finland. The completeness and accuracy of data from the Finnish Health Care Register and the Cause-of-Death Register are suitable for assessing hip fracture treatment [23]. Complete follow-ups of both fracture patients and population are strengths of our study. It may also be assumed that surgical practices, anaesthetics, and postoperative treatment remained unchanged during the 2-year catchment period of fracture patients. A control cohort with corresponding age included the whole Finnish population and its mortality was registered comprehensively. To our knowledge, such a comparison has not previously been made in the English literature.

Our study also has several limitations. Persons with medical and functional deficits are more likely to sustain hip fracture than healthy people; moreover, they have an increased mortality risk even without hip fracture. This might result in an overestimated risk of death in hip fracture patients compared to the general population. The other problem related to comorbidities might be the difficulty in identifying the "ultimate" cause of death. Data on patient comorbidities were retrospectively collected from the original patient records, which are usually based on the information received from the previous hospital records, referral documents, and patient and/or proxy interviews. They may not always be reliable or fully comprehensive. We had no information on the frequency of autopsies in cases and controls or other possible differences in determination of the cause of death. In general, autopsies are seldom performed in older people. Furthermore, we did not have information on postoperative complications or functional recovery. According to Vestergaard et al. [1], the major causes of the excess mortality after fracture were complications related to the fracture event. Because there are regional differences of mortality in Finland, patterns of death of hip fracture patients and the general population in Satakunta should be analyzed in future studies.

Our study analyzed excess mortality, i.e., deaths due to hip fracture that might be prevented, from the scope of cause of death. To reduce mortality after hip fracture, optimal treatment of all major comorbidities should be emphasized. One measure toward achieving this goal might be improved treatment after discharge from hospital as primary health care becomes responsible for the treatment. Specialist medical assessment and management of older people with hip fracture before and after surgery have been recommended [2]. Interventions such as nutritional supplementation and dietetic assessment, comprehensive multidisciplinary intervention programs, and in-hospital programs might improve outcomes, including mortality after hip fracture [24, 25]. Furthermore, enrolling specially educated personnel in hospitals treating fractures might improve the secondary prevention of fractures [26]. Most of these measures, however, are hospital-focused and long-term cooperation between primary health care and specialist health care needs to be enhanced to improve survival after hip fracture.

The present study showed that during the follow-up up to 9 years, the age- and sex-standardized all-cause mortality of hip fracture patients was 3-fold higher than that of the general population. A similar trend was observed for each cause-of-death category.