Age-adjusted incidence rates of hip fractures between 2006 and 2009 in Rabat, Morocco
This study, characterizing the incidence of hip fracture in the province of Rabat, showed that age- and sex-specific rates remained stable between 2006 and 2009. The demographic projections estimated for Morocco indicate that between 2010 and 2030, the expected annual number of hip fractures would increase about twofold.
No data on hip fracture incidence trends exist from Africa. The aim of the study was to determine time trends in hip fracture rates for the province of Rabat and to forecast the number of hip fractures expected in Morocco up to 2030.
All hip fracture cases registered during the years 2006–2009 were collected at all the public hospitals and private clinics with a trauma unit and/or a permanent orthopedic surgeon across the province.
Over the 4-year period, 723 (54.3 %) hip fractures were recorded in women and 607 (45.6 %) in men. The age- and gender-specific incidence of hip fracture rose steeply with advancing age. Hip fractures occurred later in women 75.0 (10.7) years than in men 73.3 (11.0) years (p = 0.014), and its incidence was higher in women than in men [85.9 (95 % CI 79.7–92.2) per 100,000 person-years vs. 72.7 (95 % CI 66.9–78.5)]. The incidence remained globally stable over the period study, and the linear regression analysis showed no significant statistical difference. For the year 2010, there were 4,327 hip fractures estimated in Morocco (53.3 % in women). Assuming no change in the age- and sex-specific incidence of hip fracture from 2010 to 2030, the number of hip fractures in men is expected to increase progressively from 2,019 to 3,961 and from 2,308 to 4,259 in women.
The age-specific incidence of hip fracture between the years 2006 and 2009 remained stable in Morocco, and the number of expected hip fractures would double between 2010 and 2030.
KeywordsHip fractureHip fracture incidenceMoroccoOsteoporosis
Osteoporotic fractures are a major public health concern worldwide as the number of older people in the world is increasing . Hip fractures account for a large component of the morbidity, mortality, and cost of osteoporosis. However, substantial variation has been reported in hip fracture incidence rates around the world [2, 3]. Age-adjusted rates seem to be highest in Scandinavia and in North American populations, with almost sevenfold lower rates in southern European countries . Fracture rates are intermediate in Asian populations and Latin American populations. Among different ethnic populations, the highest fracture rates are seen in Caucasians and the lowest in blacks and rates seem to be lower in rural than in urban areas . There is also a north–south gradient, particularly in Europe, where more hip fractures occur in North Europe compared to the South .
Hip fracture incidence has been shown to increase exponentially with age, and the total number of fractures is expected to rise due to population aging . In most countries, the number of elderly individuals is set to increase due to cohort effects and increases in life expectancy. In Europe, the total population will not increase markedly over the next 25 years, but the proportion accounted for by the elderly will increase by 33 %. In the developing world, the total population as well as life expectancy of the elderly will increase by more than twofold over the next 25 years, so that osteoporotic fractures will assume even greater significance for health care. In Morocco, the proportion of persons >65 years will double in less than 15 years  and life expectancy is improving dramatically (42 years in the mid-1950s, 59 years in 1980, 65 years in 1987, and 74.8 years in 2010) .
Only a limited number of studies investigated actual trends of the hip fracture incidence. Recent studies showed that over and above the increasing population at risk, there has been an increase in age- and sex-specific incidence of fractures in many communities. However, the majority of analyses found a leveling off or even a decrease of the age-adjusted hip fracture incidence [3, 7, 10].
Data about hip fractures in Africa are scarce. Only two publications from Africa reported epidemiology of hip fractures: one from Morocco  and the other from Cameroon . These two studies (both cross-sectional) reported the lowest hip fracture incidence rates in the world. No data about incidence trend exist from African countries. The objective of our study was to evaluate the incidence rate of hip fracture from 2006 to 2009 in the population of the province of Rabat, a large area of over two million people in the northeast of Morocco, and to evaluate differences in trends for sex and age groups and to forecast the number of hip fractures expected in Morocco over the coming years up to 2030.
Materials and methods
Morocco is a country located in the northwest of Africa with a population estimated to 32 million (99.2 % are Arab/Berber considered as a Caucasian ethnicity). Rabat province (called Rabat-Salé-Zemmour-Zair) is located at a latitude of 34° N–6° W and an altitude of 75 m. Rabat city is the capital of Morocco. The area of Rabat province is approximately 9,580 km2 (1.4 % of Morocco surface area). There are four distinct seasons, mild in the spring and autumn, and a hot summer (25–36 °C) and cold winter (4–20 °C). There are typically about 18 h of daylight in summer and 10 h in winter. The means rainfall is 46.3 mm/year. The economy of Rabat province is based on agriculture. In Morocco, less than 30 % of the population is covered by a health insurance system whereas free health care is provided for all people in the public hospitals.
There are a total of five public hospitals (two university centers and three regional hospitals) with an orthopedic department located throughout Rabat Province. There are 37 private clinics in the region. Eight of them have at least one orthopedic surgeon, and we could have access to the registers of the five most important ones, which had a trauma unit and a reliable registry. The remaining three clinics are small structures, which did not have a permanent surgeon at the period of the study. Moreover, their data were not exploitable and were then excluded from the study. Using the collected data from the recruitment of the private clinics and a direct contact with concerned orthopedists, we estimated that more than 95 % of the hip fractures treated in the private sector were collected. Most of residents of Rabat province with hip fracture are treated at one of the five public hospitals (80 % in our study). Patients who present to another facility of the public sector are automatically referred to one of these hospitals. All public hospitals are the biggest in their area and situated in the center of town serving the total population from all social groups and all ages. In all the visited structures, a register is maintained in the inpatient department of all patients who are admitted, which includes the date, the patient’s name, age, and gender, diagnosis of the fracture, and the patient’s home address. The admitting doctor is responsible for making the assessment using both a clinical and a radiological examination, before the entry in the register is made. In addition, there is a medical record office in each hospital, where the original medical records of patients are routinely kept and organized. In this study, the registers of hip fractures from all these structures were scrutinized and then confirmed by examining original medical records for both inclusion and exclusion criteria. Hip fractures were reviewed for all patients using information from registers and medical records.
Thus, information about all patients who were resident in Rabat province and who had sustained a hip fracture from 1 January 2006 to 31 December 2009 was obtained between October 2010 and April 2012. Exclusion criteria were nonresidents receiving treatment in Rabat, fractures due to major trauma (car crash for example), and fracture due to cancer metastases at the fracture site. If patients were admitted to more than one hospital for the same fracture, these patients were only recorded at the hospital where surgery was performed. The fractures were classified as either cervical or trochanteric according to the description in the medical record. Using the population of Rabat on 2004 (Morocco national census) and population projections for 2006–2030 developed and kindly provided by the Demographic Study and Research Centre , the age-specific and gender-specific annual incidence rates were calculated for age groups 50–54, 55–59, 60–64, 65–70, 70–75, and 75 and over and expressed as fractures/100,000 inhabitants/year as well. We calculated the ratios of hip fracture rates in men vs. women based on these age-adjusted rates. The incidence of hip fracture presented here was based on only patients over 50 years of age. For comparison of our results to those published from other countries, we calculated the age standardized incidences using the same reference population, the US Census 2000 white population. This allowed for a comparison of standardized rates for Morocco with similarly derived rates for other countries worldwide. Student’s t test and the chi-square test were used for statistical analysis. p values less than 0.05 were considered to be significant. A log linear regression analysis was used to assess the trend of hip fractures incidence between 2006 and 2009. All calculations were carried out in Microsoft Excel 2007 for Windows and SPSS v 17.0 (Gary, NC).
Incidence of hip fracture (rate/100,000) in Moroccan women and men by age and sex between 2006 and 2009 adjusted to the Morocco 2004 census population and to the 2000 US white population
There was no sex difference in the type of hip fracture. Overall, in both men and women, the number of trochanteric fractures was higher than cervical fractures (60.2 vs. 39.4 % in men and 61.3 vs. 37.7 % in women; p > 0.05). Women had a trochanteric to cervical ratio of 1.47 compared to men, at 1.43. The total number of fractured patients in each month during the observation period was highest in January (9.3 %) and lowest in March (5.2 %), showing no seasonal trends. The distribution of hip fractures according to the sector of medical activity showed that 1,006 (79.6 %) hip fractures were recorded in the public sector (51.8 % in women) and 257 (20.4 %) in the private sector (52.0 % in women).
The present study documents hip fracture risk in Morocco and confirms the results of our previous study  that showed that the risk is low in a worldwide perspective. It also estimates age-standardized rates to the US 2000 white population, and compares them to similarly calculated figures for other countries from the five continents. The age- and gender-standardized incidence rates in this study were found to be comparable to those reported in Brazil , higher than those reported in China , Korea , and Ecuador , and lower than reported rates in Lebanon , Kuwait , Iran , Australia , and most of European [21–23] and American countries [24–26].
To date, there has been no information available on hip fracture trends in Morocco or indeed the African continent. The present study finds that the age-specific incidence of hip fracture remained stable between the years 2006 and 2009. However, the projection estimation showed that the number of expected hip fractures would double between 2010 and 2030. This increase is largely a consequence of an aging overall population. We must specify that we did not consider a temporal trend of hip fracture incidence rates, and therefore, projections of hip fracture numbers in the future were based entirely upon population demographics, assuming a stable age-specific incidence rate. Thus, longitudinal studies are required to establish the trends in age-specific hip fracture incidence rates in Morocco in order to make such projections more accurate.
The incidence of hip fracture increased exponentially in our study as it is the case in most published studies. However, it has been shown in one study  that hip fracture incidence increases exponentially with age in women between 60 and 84 years of age and that the incidence continues to increase between ages 85 and 95, albeit not exponentially. Thus, assuming an exponential increase in incidence after age 85 could lead to approximately 70 % overestimation of the number of cases. In our study, we had data compiled for subjects over 75 because their absolute number is very low in our population so we could not verify this hypothesis.
The risk of hip fracture varies remarkably around the world . Decreases in age-specific rates have occurred in those countries with the higher hip fracture risks, whereas increases in incidence with time are consistently found in those countries with the lower risks . A recent review  reveals that there have been substantial temporal trends in the age-specific rates of hip fracture during recent decades. Although there are a few exceptions, age-specific incidence rates rose in western populations until around 1980 and have subsequently reached a plateau or decreased . Recent studies show that the incidence of hip fracture appear to have attenuated or leveled off in Canada  and Australia , and decreased in the USA , Switzerland , Netherlands , France , Finland , and Norway , whereas slight increases have been observed in some other countries .
Many hypotheses have been proposed to explain the variation in hip fracture incidence rates and secular trends among different countries. Hypotheses relating to the variation in risk between countries for hip fracture include exposure to risk factors such as sunlight (geographical latitude), vitamin D deficiency, duration of fertile life, risk of falling, and prenatal nutrition, all of which could affect the risk of fractures in later life. Lifestyle factors such as physical activity, diet, and smoking might also contribute. Ecological studies do not suggest important roles for these risk factors with the possible exception of body mass index and physical activity . Another explanation include a more healthy aging population, a greater average body mass index, an improved dietary intake in subsequent generations, and a more comprehensive diagnosis and pharmacological treatment of osteoporosis in the elderly population .
All of these hypothetical mechanisms are plausible. However, it will be important to determine which factors are truly responsible for the heterogeneity of fracture risk and the changes in secular trend. Many of such factors are reversible and the prevention of hip fracture in communities with presently low rates might be feasible. Failing this, the present study provides a warning to alert the general population, health institutions, and policy decision makers to plan and implement strategies for detecting the population at risk and implementing primary and secondary prevention programs in Morocco.
The hip fracture incidence in our study was slightly lower in men than in women. It is classically reported that hip fracture incidence is about twofold higher in women than in men worldwide. However, probability estimates of hip fracture were found to be modestly lower in men than in women in a recent extensive review  (lower by only 23 %). The closer approximation between sexes for the probability estimate arises because the risk of hip and other osteoporotic fractures is more or less identical in men and women of the same age and femoral neck BMD. The somewhat higher probability estimates in women reflects mainly the lower death risk in women compared with men.
A limitation of this study is that it is retrospective and as such is subject to errors of this kind of studies. Incidence based on hospital data would be underestimated if many hip fractures were not diagnosed or treated in these hospitals. However, Rabat, which is the capital of Morocco, is a well-developed city and has the leading public hospitals in the country. It is more common for people resident outside of the city to come to Rabat for health care than for residents of the city to seek care elsewhere. It is unlikely, therefore, that significant underreporting of hip fractures due to treatment outside the city would have introduced a large error into the study. In fact, Ibn Sina Hospital is the greatest hospital in Morocco where all the serious cases are referred (more than 42 % of our cases). Moreover, a great proportion of the Moroccan population is poor and there is no generalized health insurance program, so in spite the fact that there are many private clinics in the region, almost all individuals cannot afford to pay the cost of treatment for fractures in private clinics and gather to public hospital where health care is free (80 % of our patients). We could have the data of the most important private clinics of the region, and only three small clinics without a trauma unit and without a permanent orthopedic surgeon during the period study did not have a correct registry and exploitable data, and were then excluded from the study. Using a short survey of a sample from the orthopedic surgeons of the region (data not shown) and the collected data, we estimated that more than 95 % of the hip fractures treated in the private clinics were collected. Another potential source of inaccuracy is the potential to duplicate patient numbers because of recurrent admissions to or transfer between hospitals for a single hip fracture episode. We took these considerations into account when constructing our search protocol, and by cross-checking by an extensive manual search across the registers.
In summary, our study showed that the age-specific incidence of hip fracture in Morocco is low in a worldwide perspective and remained stable between the years 2006 and 2009. However, the projection estimation showed that the absolute number of expected hip fractures would double between 2010 and 2030. Public health strategies should be undertaken to reduce the incidence of the hip fractures in the future.
The authors thank the orthopedic departments of the five public hospitals of Rabat province: Ibn Sina Hospital (Prof. Moradh El Yaacoubi), Military Hospital Mohammed V (Prof. Jaafar Abdeloihab and Prof. Kacem Chagar), Moulay Abdellah Hospital of Salé, Sidi Lahcen Hospital of Temara, and Provincial Hospital of Khemisset, and Prof. Nabil Bousselmame, Prof. Farid Ismail, Dr. Rachid Nazih, Dr. Mohamed Missoum, Dr. Mounir Sbiti, Dr. Samir El Blidi, and Dr. Mohamed Zidouh for the help and assistance during the data collection.
Conflicts of interest