Alzheimer's Disease Correlates with Greater Risk of Hip Fracture in Older People: A Cohort in Taiwan

Abstract

To the Editor: Alzheimer's disease and hip fracture are two common disorders in older people, and both result in severe socioeconomic burden. Growing evidence has demonstrated that individuals with Alzheimer's disease have 2.1 to 3.2 times greater risk of hip fracture.1-3 Little evidence is available about the relationship between Alzheimer's disease and risk of hip fracture in older people in Taiwan, so this cohort study was conducted to explore this question by analyzing the Taiwan National Health Insurance program database. Information about the program can found in previous studies.4, 5 In this cohort study, the diagnosis of Alzheimer's disease and hip fracture was based on International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9) codes. Nine hundred thirty-six individuals aged 65 and older with newly diagnosed Alzheimer's disease (ICD-9 code 331.0) were chosen as the Alzheimer's disease group (429 men, 507 women, mean age 78.2 ± 6.8, mean follow-up 3.5 ± 2.9 years) and 3,744 without Alzheimer's disease as the control cooperator group (1,716 men, 2,028 women, mean age 77.1 ± 7.1, mean follow-up 4.4 ± 3.2 years) from 2000 to 2010. The index date was defined as the date of diagnosis of Alzheimer's disease. Both groups were matched according to sex, age, and index year. Both groups were followed up to determine the incidence of hip fracture (ICD-9 code 820) until a subject received a diagnosis of hip fracture or until December 31, 2010. Subjects with hip fracture, other dementia (ICD-9 codes 290.0, 290.1, 290.2, 290.3, 290.4, and 294.1), or mental retardation (ICD-9 codes 317–319) diagnosed before index date were excluded. The Alzheimer's disease group had a significantly higher incidence of hip fracture than the non-Alzheimer's disease group (27.8 vs 11.7 per 1,000 person-years, 95% confidence interval (CI) = 2.02–2.80). The incidence rates, as stratified according to sex, age, and follow-up period, were all significantly higher in the Alzheimer's disease group. Women with Alzheimer's disease had a higher incidence of hip fracture (30.8 per 1,000 person-years) than men (24.0 per 1,000 person-years). Subjects with Alzheimer's disease aged 75 to 84 had the highest incidence of all subgroups (incidence rate 37.8 per 1,000 person-years). The stratified analysis according to follow-up period showed a higher risk of hip fracture within 2 years of Alzheimer's disease diagnosis (incidence rate ratio = 3.30, 95% CI = 2.78–3.92). Overall, 59.3% (54/91) of hip fracture cases in the group with Alzheimer's disease occurred within 2 years after index date, as opposed to 36.8% (70/190) in the group without Alzheimer's disease (Table 1). Epidemiological studies have reported that Alzheimer's disease correlates with greater risk of hip fracture in western countries.1-3 The present study found that the incidence rate ratio of hip fracture was 2.38 in individuals with Alzheimer's disease compared with the group without Alzheimer's disease. It also found that the incidence rates of hip fracture in individuals with and without Alzheimer's disease (27.8 and 11.7, respectively, per 1,000 person-years) were higher than that in a previous study in the United Kingdom in 2011 (17.4 and 6.6, respectively, per 1,000 person-years).3 This indicates that the quality of care of older people should be further improved in Taiwan. It was also found that the incidence of hip fracture was higher within 2 years after index date, indicating that individuals with newly diagnosed Alzheimer's disease should be closely followed during the first 2 years because of their risk of hip fracture. Alzheimer's disease is associated with 2.4 times greater risk of hip fracture in older people in Taiwan. Preventive falling strategies should be adopted in older people with Alzheimer's disease to reduce the risk of hip fracture. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. This study was supported in part by Taiwan Department of Health Clinical Trial and Research Center of Excellence (DOH102-TD-B-111–004) and China Medical University Hospital (Grant number 1MS1). Author Contributions: Lai S.-W.: conception of article, conducted study, interpreted data, initiated draft of article, critically revised article. Chen Y.-L.: conducted study, interpreted data, initiated draft of article, critically revised article. Lin C.-L.: conducted statistical analysis, critically revised article. Liao K.-F.: conducted study, critically revised article. Sponsor's Role: The funding agency did not influence the study design, data collection and analysis, decision to publish, or preparation of the manuscript.