Factors associated with fragility fractures in women over 50 years of age: a population-based household survey

Fatores associados a fraturas por fragilidade óssea em mulheres acima de 50 anos de idade: um estudo de base populacional

Factors associated with fragility fractures in women over 50 years of age: a population-based household survey

Fatores associados a fraturas por fragilidade óssea em mulheres acima de 50 anos de idade: um estudo de base populacional

Luiz Francisco Baccaro^I; Vanessa de Souza Santos Machado^I; Lúcia Costa-Paiva^I; Maria Helena Sousa^II; Maria José Osis^II; Aarão Mendes Pinto-Neto^I

^IDepartment of Obstetrics and Gynecology, Faculdade de Ciências Médicas, Universidade Estadual de Campinas - Unicamp - Campinas (SP), Brazil

^IICenter for Research on Reproductive Health of Campinas - Cemicamp - Campinas (SP), Brazil

^{Correspondence}

ABSTRACT

PURPOSE: To analyze the prevalence of and factors associated with fragility fractures in Brazilian women aged 50 years and older.

METHODS: This cross-sectional population survey, conducted between May 10 and October 31, 2011, included 622 women aged >50 years living in a city in southeastern Brazil. A questionnaire was administered to each woman by a trained interviewer. The associations between the occurrence of a fragility fracture after age 50 years and sociodemographic data, health-related habits and problems, self-perception of health and evaluation of functional capacity were determined by the χ² test and Poisson regression using the backward selection criteria.

RESULTS: The mean age of the 622 women was 64.1 years. The prevalence of fragility fractures was 10.8%, with 1.8% reporting hip fracture. In the final statistical model, a longer time since menopause (PR 1.03; 95%CI 1.01-1.05; p<0.01) and osteoporosis (PR 1.97; 95%CI 1.27-3.08; p<0.01) were associated with a higher prevalence of fractures.

CONCLUSIONS: These findings may provide a better understanding of the risk factors associated with fragility fractures in Brazilian women and emphasize the importance of performing bone densitometry.

Keywords: Osteoporotic fractures/etiology; Menopause/; Risk factors; Osteoporosis/complications; Life style

RESUMO

OBJETIVO: Analisar a prevalência e os fatores associados a fraturas por fragilidade óssea em mulheres brasileiras com 50 anos ou mais.

MÉTODOS: Estudo transversal com base populacional, conduzido de 10 de maio de 2011 a 31 de outubro de 2011, que incluiu 622 mulheres com idade >50 anos, residentes em uma cidade na região Sudeste do Brasil. Foi aplicado um questionário por entrevistadores treinados. As associações entre ocorrência de fraturas por fragilidade óssea após os 50 anos e dados sociodemográficos, hábitos e problemas de saúde, autopercepção de saúde e avaliação da capacidade funcional foram realizadas por meio do teste do χ² e da regressão de Poisson com critério de seleção de variáveis backward.

RESULTADOS: A idade média das 622 mulheres foi 64,1 anos. A prevalência de fraturas por fragilidade óssea foi de 10,8%, com 1,8% relatando fratura de quadril. No modelo estatístico final, apresentar maior tempo de menopausa (RP 1,03; IC95% 1,01-1,05; p<0,01) e osteoporose (RP 1,97; IC95% 1,27-3,08; p<0,01) se associaram a maior prevalência de fraturas.

CONCLUSÕES: Esses dados podem ajudar a melhorar o conhecimento sobre os fatores associados a fraturas por fragilidade óssea em mulheres brasileiras e enfatizar a importância da realização da densitometria óssea.

Palavras-chave: Fraturas por osteoporose/etiologia; Menopausa; Fatores de risco; Osteoporose/complicações; Estilo de vida

Introduction

The aging of the Brazilian population has led to increases in the proportion of women aged >50 years, such that this age group accounted for 21.7% of the female population in 2010. With the increase in life expectancy, it has been projected that a Brazilian woman currently aged 50 years will survive for about 31 more years¹. Fragility fractures are a major health problem in the elderly, with hip fractures in particular being a problem not only for the patient, but also in terms of higher healthcare costs². The mortality rate during the first year after a hip fracture is around 10-35%³, and it has been estimated that only about 50% of individuals who have suffered a hip fracture will be able to reestablish their daily activities⁴. Recent studies have estimated the prevalence of bone fragility fractures in Brazilian women at 11.5-21.3%^5-7, and the annual incidence of hip fracture adjusted for age was estimated to be 199 per 100,000².

Recently, mathematical models that combine clinical risk factors and measurements of bone mineral density (BMD) at the femoral neck have been used in several countries to estimate the risk of fragility fractures, and thus plan the therapeutic strategy for each individual⁸. Factors associated with a higher prevalence of fractures in Brazil include patient age, family history of hip fractures, early menopause, sedentary lifestyle, poor quality of life, high intake of phosphorus, diabetes mellitus, use of benzodiazepines, low BMD, and recurrent falls⁹. In addition, the FRAX^® fracture assessment tool was released for use in the Brazilian population¹⁰.

Knowledge of the risk factors associated with fragility fractures is important in formulating appropriate public health spending plans in a vast country like Brazil, as well as to improve and customize types of treatment. To better understand the prevalence of, and factors associated with, bone fragility fractures in Brazilian women, we assessed these parameters in women aged >50 years living in a city in southeastern Brazil.

Methods

This is a secondary analysis of a cross-sectional study entitled "Health conditions in women over 50 years: A population-based study in Campinas, São Paulo", conducted from May 10 to October 31, 2011 in the city of Campinas, São Paulo, Brazil. A total of 66 census sectors were selected in the city by simple random sampling or equal probabilities of selection, based on a list supplied by the Brazilian Institute of Geography and Statistics (IBGE), and classified according to the identification number of each sector. The IBGE census sectors were numbered and their geographical limits were clearly defined. The sectors were classified in accordance with the database of the 2000 census for the city of Campinas. All census sectors with at least ten women aged 50 years or older residing in them were included in the random selection process. The sectors in which there were fewer than ten women in this age group were grouped together with the consecutively numbered neighboring sector. Research assistants, guided by maps of each census area, went to odd-numbered houses and enquired whether any of the residents were women aged 50 years or older. Any woman who fulfilled the eligibility criteria was invited to participate in the study. If she agreed to participate, a questionnaire was implemented in person or by telephone by interviewers trained at the Campinas Center for Research and Control of Maternal and Child Diseases. This was repeated until 10 eligible women were obtained in each sector. If the required number of women was not achieved in a particular sector, visits to homes in that sector were reinitiated, going to those that had not been previously visited. A total of 721 women were invited to participate in the study. Ninety-nine women (13.7%) declined to participate, principally reporting a lack of time in which to answer the questionnaire. Therefore, the final sample comprised 622 women. All women signed free and informed written consents before their interviews. The study was approved by the Research Ethics Committee of UNICAMP under the number 1012/2010.

According to IBGE, the population of Campinas in 2007 was 1,039,000, of whom approximately 545,000 were women. Approximately 131,800 of these women were aged 50 years or older. As this was a survey on different morbidities, hypertension was taken into consideration as the most prevalent morbidity in women in Brazil, with an estimated prevalence of 56.3%. A type 1 (alpha) error of 5% and a margin of error of 5% were considered. The resulting sample size was then increased by 10% to compensate for a possible loss of subjects; therefore, the final sample size was established as 657 women.

The study selected women aged 50 years or older residing in the city of Campinas, São Paulo, Brazil.

Explicit refusal to participate in the study or any factor preventing the interview from taking place, such as illness, personal commitments, or incompatibility of schedules, constituted exclusion criteria. Women with a cognitive disability that prevented them from answering the questionnaire or those suffering from dementia were also excluded.

The dependent variable was the presence of a fragility fracture at age 50 years or above. This was established using the question: "Has a doctor ever told you that you had broken a bone at age 50 years or above?", with responses "yes", "no" or "do not know". Of women answering "yes" to the question, those who reported having had only a fractured tibia/leg, foot or anklebone were excluded because fractures at these sites may not have been fragility fractures⁵.

The independent variables were age; education; marital status; skin color; monthly income; body mass index; difference between current weight and weight at 20-30 years of age; smoking; if a past or current smoker, the number of cigarettes/day; alcohol consumption; frequency of alcohol consumption; weekly physical exercise; frequency of physical exercise; having to stay in bed for more than half a day during the preceding 2 weeks due to illness or pain; number of days spent in bed during the previous 2 weeks; hospitalization during the previous year; number of months since the last medical consultation; treatment with any drugs acting on the central nervous system (CNS), medications used to treat menopausal symptoms, anti-rheumatic drugs, medications to treat osteoporosis, antihypertensive drugs, antilipidemic agents, antidiabetic drugs, cardiac drugs, thyroid hormones, anti-ulcer drugs, and analgesics; and use of alternative treatments. Other factors included having private medical insurance; stopping menstruation more than one year earlier; time since menopause in years; menopausal treatment, including hormonal treatment and treatment with natural menopausal remedies; duration of menopausal treatment in months; problems maintaining balance while walking, taking a bath, dressing, or going down stairs; falls within the previous 12 months; fear of falling; whether this fear interfered with routine activities; self-perception of health; and difficulties in feeding, taking a bath, going to the toilet, running, lifting heavy items, participating in sports or heavy work, pushing a table or doing housework, climbing stairs, crouching or kneeling, walking 100 m and walking more than 1 km.

Other independent variables included a diagnosis of diabetes, time since diagnosis of diabetes, and receipt of treatment for diabetes; diagnosis of cancer, time since diagnosis, and receipt of treatment for cancer; diagnosis of osteoarthritis and time since diagnosis; diagnosis of hypertension and time since diagnosis; use of antihypertensive medication; previous heart attack; previous stroke, time since diagnosis, and sequelae due to stroke; diagnosis of bronchitis, asthma, or emphysema; diagnosis of osteoporosis or bone weakness, time since diagnosis, and receipt of treatment for osteoporosis; diagnosis of glaucoma or cataract and time since diagnosis of cataract; wearing of glasses or contact lenses and ability to see well; use of a hearing aid(s) and ability to hear well; urinary incontinence; active sex life; and number of comorbidities.

The questionnaire used in the present study was based on three preexisting questionnaires: two developed in Brazil^11,12 and another in the USA¹³. It was structured in five sections related to the data of interest to the study: a sociodemographic evaluation, health-related habits, self-perception of health, evaluation of functional capacity, and health-related problems. The variables were based on the women's self-reported responses.

Initially, a simple descriptive analysis of the cases of fragility fractures was performed using a frequency distribution. Women who reported exclusively fracture of the tibia/leg, foot or anklebones were then excluded from the analysis. Next, a bivariate analysis using the χ² test¹⁴ was performed to assess the association between the dependent variable and the independent variables. Finally, a Poisson multiple regression model was constructed¹⁵, with the prevalence ratios (PRs) and respective 95% confidence intervals (95%CI) calculated to identify significant independent variables using backward selection. The significance level was established at 5% and the cluster sampling (census sector) was used in the bivariate and multiple analyses. The analyses were performed using SPSS^®, version 20.0 (IBM Corp. , Armonk, NY, USA) and STATA^® version 7 (StataCorp LP, TX, USA).

Results

A total of 622 women aged 50 years or older answered the questionnaire. The mean age was 64.1 years, 70.4% had at least 8 years of education, 52.2% were not living with a partner, 70.4% were white, 53.6% reported a monthly family income of R$1.500 or less, 37.9% had a BMI between 25 and 29.99, 36.3% were smokers or had previously smoked, 15.0% drank alcohol regularly, 36.2% practiced physical exercise on a weekly basis, and 21.3% reported being affected by osteoporosis.

After exclusion of women with fractures exclusively in the foot or ankle or missing data (n=18), the prevalence of fragility fractures at age 50 or over in the study population was 10.8% (n=65), with 1.8% reporting hip fracture (n=11) (Table 1). In the bivariate analysis, an association was observed between fragility fractures and age (p<0.01), white race (p=0.04), weight loss compared with weight at 20-30 years (p=0.02), not doing physical exercise weekly (p=0.04), a longer time since the menopause (p<0.01), fear of falling (p=0.02), fear of falling that affected their daily activities (p<0.01), reporting osteoporosis (p<0.01), multimorbidity (p=0.02), and not being sexually active (p<0.01) (Table 2). Regarding the variables in self-assessment of functional capacity, there was an association between fragility fractures and having difficulty pushing a table or doing housework (p<0.01), being unable to climb stairs (p<0.01), and being unable to crouch or kneel down (p<0.01) (Table 3).

In the multiple regression analysis, a higher prevalence of fragility fractures at 50 years or older was associated with a longer time since the menopause (PR 1.03; 95%CI 1.01-1.05; p<0.01) and having osteoporosis (PR 1.97;95%CI 1.27-3.08; p<0.01).

Discussion

The aim of this study was to evaluate the prevalence of fragility fractures and their associated risk factors in women aged >50 years in the city of Campinas, São Paulo, Brazil. The overall prevalence of bone fragility fractures was 10.8%, whereas the prevalence of femoral/hip fractures was 1.8%. These results are similar to those obtained in national studies, which estimated that the prevalence of fragility fractures in older women was 11.5-21.3%^5-7, and the prevalence of femoral/hip fractures was 1.26%⁷.

Although BMD has been used as a predictor of fragility fractures, this parameter has yielded unclear results. Most individuals who suffer fractures do not have BMDs ​consistent with osteoporosis according to World Health Organization criteria. In addition, younger individuals with densitometric osteoporosis, but without other risk factors, have relatively low rates of fractures¹⁶. In recent years, efforts have been made to develop mathematical models that combine BMD and clinical risk factors to predict the risk of fragility fractures, and thus to individualize therapeutic strategies⁸. In Brazil, the clinical risk factors for fragility fractures have not yet been fully determined, although the Brazilian Osteoporosis Study (BRAZOS) identified advanced age, family history of hip fracture, early menopause, sedentary lifestyle, poor quality of life, high intake of dietary phosphorus, diabetes mellitus, use of benzodiazepines and recurrent falls during the previous year as risk factors for fragility fractures⁵. In addition, the São Paulo Osteoporosis Study (SAPOS) identified age, duration of menopause, and family history of hip fracture as risk factors for fragility fractures, and regular physical activity as a protective factor⁷. Recently the FRAX^® fracture assessment tool was released for use in the Brazilian population; this tool can be used to calculate fracture risk and plan the most appropriate type of therapy for each patient¹⁰.

In the present study, bivariate analysis identified several factors previously associated with fragility fractures, including age, white race, lower weight than at age 20-30 years, a longer time since menopause, and osteoporosis¹⁷. Other factors identified in our bivariate analysis may be related to the aging process itself, including an inactive sexual life and multimorbidity. There was no association between falls and fracture prevalence, but there was an association between fear of falling and fracture prevalence. This finding suggests that women who have experienced a fracture are afraid of falling and of a possible new fracture, with a resultant reduction in their quality of life. A recent population-based study showed that the factors associated with falls in Brazilian women were trouble maintaining balance when walking, alcohol consumption, admission to a hospital during the previous 12 months, and cataracts. Administration of some type of treatment for menopause and having health insurance were associated with a lower prevalence of falls¹⁸.

In addition to factors intrinsic to the individual, the assessment of functional capacity has been used to predict the chances of having osteoporosis and fragility fractures. In the present study, we found an association between a higher prevalence of fractures and lack of weekly physical exercise, difficulties pushing a table or doing housework, and inability to climb stairs, crouch or kneel down. Women with impaired functional capacity have a higher risk of osteoporosis¹⁹. In addition, a prospective cohort study of postmenopausal Finnish women demonstrated that factors associated with an increased risk of bone fracture included failing to maintain balance on one foot for more than 10 seconds, grip strength, and difficulty walking 100 meters²⁰.

In the final statistical model, Poisson regression identified only two variables independently associated with a higher prevalence of fragility fractures: a longer time since the menopause and osteoporosis. A previous prospective longitudinal study in white women showed bone loss of 10.5% at the spine, 5.3% at the femoral neck, and 7.7% throughout the entire body during the first 5-7 years after menopause. Although these losses may have been due to the natural aging process, low serum estrogen concentrations, leading to imbalances between bone formation and resorption, were thought to be responsible for about two-thirds of bone loss²¹. The FRAX^® tool includes hypogonadism and menopause before age 45 years as causes of secondary osteoporosis⁸. In older women around 70 years of age, however, the risk of fracture was found to be independent of the time of menopause^22,23.

The lack of association between clinical risk factors and bone fragility fractures in our final statistical model suggests that bone densitometry may be of great importance in identifying Brazilian women who are more likely to suffer fractures due to bone fragility, especially those with a history of early menopause. In 2002, the Ministry of Health of Brazil²⁴ issued a decree (n. 1101/GM) establishing the parameters for public health system support, such as the expected amount of medical equipment. Based on these parameters, 7.1 x-ray bone densitometry machines would be available for every million inhabitants²⁴. In 2009, IBGE²⁵ reported that the total availability, in both the private and public sectors, was 5.6 bone densitometry machines per million persons in Brazil in 2005, but was only 1.5 per million in the public health system, which corresponds to 20% of the need set out by the 2002 ministerial decree. It is noteworthy that, in the current study, 21.3% of women reported being affected by osteoporosis; of these, 77.9% underwent bone densitometry to identify the pathology. Although the latter percentage was higher than expected, this study was conducted in Campinas, São Paulo, a city located in one of the richest regions of the country, where it is easier to perform diagnostic examinations both through the public and private health systems.

This study had several limitations, especially those associated with its cross-sectional design, which has known statistical limitations. The variables were based on self-reports, and it was not possible to confirm the reported diseases and conditions by laboratory tests, X-rays and bone densitometry. However, since this is a population-based study, we believe that these limitations did not affect the final analysis, because any errors may have resulted equally in an increase or decrease in diagnosis of the conditions investigated. Furthermore, this study is part of a large population survey on multimorbidities, and some variables, such as family history of fragility fractures, could not be obtained.

In conclusion, the prevalence of bone fragility fractures in women aged >50 years in Campinas was similar to that reported in previous national studies. Factors associated with a higher prevalence of fractures were a longer time since menopause and osteoporosis. These findings may provide a better understanding of the risk factors associated with clinical fragility fractures in Brazilian women. They also emphasize the importance of performing bone densitometry, especially in women who use the public health system. This may result in earlier therapy, decreasing the incidence of fragility fractures throughout the country.

Acknowledgement

To Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) which have financed this study through the Process No. 2010/15867-1.

Received: 02/09/2013

Accepted with modifications: 11/11/2013

Conflict of interests: none.

Study carried out at the Department of Obstetrics and Gynecology, Faculdade de Ciências Médicas, Universidade Estadual de Campinas - Unicamp - Campinas (SP), Brazil.

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Correspondence:

Luiz Francisco Baccaro

Av. Alexander Fleming, 101. Cidade Universitária Zeferino Vaz

Zip code: 13083-881. Campinas (SP), Brazil

Publication Dates

• Publication in this collection
  10 Jan 2014
• Date of issue
  Nov 2013

History

• Received
  02 Sept 2013
• Accepted
  11 Nov 2013