Abstract
Introduction
The purpose of this study was to evaluate the prevalence of sarcopenia in a cohort of healthy community-dwelling elderly in an urban area in Barcelona (Spain) for native benchmarks and compare them with those published in other geographical areas.
Material and methods
We prospectively evaluated a series of 200 healthy elderly in the community with preserved functional capacity and absence of cognitive impairment. We performed a comprehensive geriatric assessment and determined anthropometric data, muscle mass (MM) and the muscle mass index (MMI). Assessment of muscle mass was performed by bioelectrical impedance analysis (BIA). The cut-off point for defining sarcopenia MMI was established as less than 2 SD of the mean of a reference group comprising 220 healthy volunteers (20–42 years) in the same area. Results were compared with studies undertaken in the USA, France and Taiwan.
Results
The cut-off points obtained were 8.31 Kg/m2 for men and 6.68 Kg/m2 for women, being similar to those observed in France and Taiwan but different from the USA. The prevalence of sarcopenia observed was 33% for elderly women and 10% for males. On comparison of the prevalence of sarcopenia in the four populations, we observed some differences, particularly in males.
Conclusions
We have defined reference values for sarcopenia, determined by BIA, in our setting. We also observed a remarkable prevalence of sarcopenia in the healthy elderly community, especially in females, showing some differences from those in other geographical regions.
Key words: Sarcopenia, aging, muscle mass
Introduction
Human aging involves a series of changes in the different body systems resulting in a progressive loss of functionality. At the level of the skeletal muscle system there is a loss of muscle mass and strength, which is accelerated from 65-70 years and is known as sarcopenia. The consequences of these changes in muscle mass result in a loss of functional capacity and an increase in frailty and disability in the elderly which, in turn, promote the appearance of several geriatric syndromes (immobility, falls). The clinical relevance of sarcopenia depends on the total pre-muscle mass and the speed at which this is lost, being modulated by multiple intrinsic and extrinsic factors (1., 2., 3., 4., 5., 6., 7., 8., 9.). Some authors have proposed sarcopenia as a new geriatric syndrome (10). Similar to osteoporosis, sarcopenia (clinically relevant loss of muscle mass) is defined as the loss of more than two standard deviations below the normal value of muscle mass corresponding to a young population (6, 11).
There are several methods to measure total muscle mass in an individual. Among them magnetic resonance, computed tomography (“gold standard”) and dual-energy X-ray absorptiometry are highly reliability techniques but are difficult to apply in large populations because of their high cost and infrastructure requirements (6, 12., 13., 14.). Another recent technique to determine muscle mass is bioelectrical impedance analysis (BIA) which has proven to be less expensive than other methods.
Loss of functional capacity is of particular importance in the elderly since the appearance of any disability or incapacitating process may accelerate this loss with high health and socioeconomic consequences (15).
After the fifth decade this decline is reported an annual rate of approximately 1-2% and accelerates to as 3% after the sixth decade of life. According to various studies the prevalence of sarcopenia varies from 15 to 50% and increases progressively with age depending on geographic and gender variables, while the loss of muscle strength decreases from 20% to 40%, between the sixth and seventh decades raising the presence of disability three- to four-fold (16., 17., 18.). Nonetheless, no data to this respect are available in our setting.
Given the disparity of the existing data and the differences observed in different geographical areas, the aim of our study was to obtain baseline data and analyze the prevalence of sarcopenia in a cohort of healthy community-dwelling elderly for comparison with results published in literature.
Materials and Methods
Selection of subjects
We prospectively evaluated a series of 200 healthy community-dwelling elderly from 70-80 years of age, controlled in a primary care center in the urban area of Barcelona (CAPSE). Subjects were included successively over a period of 24 months. Inclusion criteria were: preserved functional capacity (Barthel Index (BI) over 90) and no cognitive impairment (Pfeiffer less than 3 errors) with a regular physical activity (participated in regular exercise at least 30 minutes a day, more than 3 days a week). We excluded patients with previous muscle disease or those receiving drugs with potencial role on the muscle function (f.e. corticosteroid therapy or hormonal therapies), with antecedents of recent illness that affects physical activity (f. e. orthopedic procedures) or wearing a peace maker.
Sample size was established by a statistical estimation on the basis of previous studies.
Comprehensive geriatric assessment
All subjects underwent a comprehensive geriatric assessment including functional and neuropsychological assessment. The functional assessment was performed by assessing the basic activities of daily living with the BI using a quantitative scale from 0 to 100. The cognitive assessment was performed using the Mini-Mental test and comorbidity was determined using the Charlson Index (ChI). Likewise, we did an anthropometric study (weight and height) to determine the body mass index (BMI) and assessment of nutritional status using the Mini Nutritional Assessment (MNA).
Young Reference Group
In order to define the reference values in our population an anthropometric assessment was made and body composition was determined in a group of healthy volunteers (20-40 years of age). We defined the presence of sarcopenia in our population as a loss of muscle mass more than 2 SD below the standard normal muscle mass of the young reference group. The sample calculation was based on previous statistical studies (19., 20.).
We analyzed the demographic variables (age and sex), anthropometric (weight, height, body mass index (BMI), muscle mass and muscle mass index (IMM).
Muscle assessment
We assessed body composition by bioelectrical impedance analysis (BIA) with a RJL Systems BIA 101 device.
The principle of BIA is that biological tissues behave as conductors of electricity and thus, this technique is based on the passage of an alternating current of low intensity and on obtaining the value of the impedance (resistance and reactance composed). The composition of the human body may thereby be calculated from these values and validated formulas (21., 22.).
The BIA study was performed with a standard technique using a single frequency of 50 KHz and the placement of four electrodes in a distal position (two electrodes at the level of the hand and two electrodes at the ipsilateral foot.) The patient was in a supine position with the lower limbs in abduction of 45 ° and the upper limbs in abduction of 30°. The values of reactance and resistance were then recorded once the record was stabilized. Muscle mass was calculated using the formula of Jansenn et al. (14):
Muscle mass (kg) = [(height2 / R * 0.401) + (3.825 * sex) + (-0.701 * age) + 5102
where height is expressed in cm, R in ohms, age in years and female sex has a value of 0 and males a value of 1. The muscle mass index (MMI) is defined as the muscle mass a person has, corrected by body surface area (muscle mass / height 2).
Muscular strength was measured in the non-dominant deltoid muscle with a myometer (Penny Giles Ltd. United Kingdom), the test was always repeated three times during a 5 minute period, with the mean value of the registrations being recorded. The existence of weakness was defined by a mean registration under 20 Kg (23).
Results were compared with studies made before in USA, France and Taiwan (18, 24., 25.).
Informed consent was obtained from all individuals for their participation in the study and approval for the study was obtained from the ethic committee of the center.
Statistical analysis
The data were analyzed using the SPSS-PC 14.0 (SPSS, Chicago, IL). A descriptive analysis was performed using absolute and relative frequencies for qualitative variables and mean (standard deviation) for quantitative variables. Comparison of groups was carried out with bivariate analysis (t test for continuous quantitative variables and Chi square for qualitative variables.) A p <0.05 was considered statistically significant.
Results
Young Reference Group
The young reference group included a total of 230 individuals (110 males and 120 females) with a mean age of 28.6 (SD± 5.42) and 28.2 (SD± 6.83) years, respectively. The main characteristics of the group and also the main results of studies undertaken before (USA, France and Taiwan) are reflected in Table 1. The anthropometric study of body composition in this group showed values of 9.58 MMI Kg/m2 for men (SD ± 0.63) and 7.56 Kg/m2 for women (SD ± 0.48). Therefore, sarcopenia in our patients was defined as an MMI <8.25 Kg/m2 for men and <6.68 Kg/m2 for women.
Table 1.
Anthropometric characteristics of the young reference group and comparative data. Mean (SD)
| Spain | China (25) | USA (18) | France (24) | |||||
|---|---|---|---|---|---|---|---|---|
| men | women | men | women | men | women | men | women | |
| n | 110 | 120 | 107 | 122 | 394 | 388 | 100 | 100 |
| Age | 28.6 (5.0) | 28.2 (6.0) | 28.7 (5.1) | 29.7 (5.9) | 30.2 (6.1) | 29.2 (6.3) | 26.7 (5.7) | 27.6 (5.9) |
| BMI (Kg/m2) | 24.58 (2.6) | 21.92 (2.2) | 24.6 (3.8) | 24.1 (5.4) | 23.9 (3) | 22.5 (3.4) | 23.2 (3.5) | 20.6 (2.5) |
| MM (Kg) | 29,88 (3) | 20,54 (1,5) | 27.3 (3.6) | 17.7 (3.7) | 32.2 (3.3) | 21 (2.5) | 32.6 (3.5) | 20 (2.2) |
| MMI (Kg/m2) | 9.65 (0.70) | 7.65 (0.49) | 8.6 (1.1) | 7.3 (0.9) | 10.4 (0.9) | 7.8 (0.8) | 10.9 (1) | 7.9 (0.7) |
BMI: body mass index; MM: muscle mass; MMI: muscle mass index
Group of elderly subjects
The group of healthy elderly from the community included 110 males and 90 females with a mean age of 73.9 (SD±3.2) and 74.9 (SD±3.2) years, respectively. The functional status was preserved (BI 98.5 (SD±2.4) and 99 (SD±3.1)) with low comorbidity (ChI 0.6 (SD±0.9) and 0.4 (SD±0.8)) and preserved nutritional status (MNA 28.7 (SD±1.2) and 28.4 (SD± 1.7))
Table 2 describes the main data on body composition and muscle mass in the healthy elderly group and also shows the main results of studies undertaken before (USA, France and Taiwan).
Table 2.
Anthropometric characteristics of the elderly group and comparative data. Mean (SD)
| Spain |
China (25) |
USA (16) |
France (24) |
|||||
|---|---|---|---|---|---|---|---|---|
| men | women | men | women | men | women | men | women | |
| n | 90 | 110 | 426 | 382 | 112 | 106 | 157 | 145 |
| Age | 74,6 (3.5) | 75,3 (3.3) | 73.6 (5.8) | 73.7 (6.1) | 64.1 (3.8) | 64.7 (3.6) | 76.6 (7) | 74.4 (6.4) |
| BMI (Kg/m2) | 26.30 (3.0) | 26,95 (4.5) | 25.9 (3.7) | 26.2 (4.6) | 26.2 (3.1) | 25.3 (3.9) | 24.4 (3.1) | 24.4 (3.7) |
| MM (Kg) | 27.01 (4.3) | 16.86 (2.2) | 22.5 (2.6) | 14.5 (2.2) | 29.4 (3.8) | 18.5 (2.2) | 26.4 (3.8) | 17 (2.7) |
| MMI (Kg/m2) | 9.8 (1.3) | 7.08 (0.8) | 7.7 (0.7) | 5.9 (0.7) | 10.1 (1.1) | 7.5 (0.8) | 9.8 (1.1) | 7.3 (1) |
| Sarcopenia (%) | 10 | 33 | 18.3 / 36.4 | 33.3 / 35.9 | 3.6 | 2.8 | 23.6 | 18.6 |
BMI: body mass index; MM: muscle mass; MMI: muscle mass index
Muscular strength was impaired in all elderly subjects with a mean of 17,7 Kg (SD± 3.3) in male and 11,9 Kg (SD± 2.9) in female. Although the loss of strength was more important in sarcopenic subjects, these differences doesn’t reach statistical significance (p= 0.2).
Discussion
The loss of muscle mass that occurs with aging has been well documented in previous studies (5., 6., 7., 8.). However, in our setting there are no data on the prevalence of sarcopenia in the elderly in the community.
The wide variation in the prevalence of sarcopenia in the elderly is due to different factors, but it mainly depends on the characteristics of the study population (general, healthy, sick, race) and the methodology used for its determination.
In studies in healthy elderly from the community the prevalence of sarcopenia is generally higher in females and increases with age. In one of the first studies performed in the United States a decade ago, the prevalence was reported to be 20% in men between 70 and 75 years of age and rose up to 50% in those over the age of 80, with the figures ranging between 25% and 40%, respectively for women (16). More recent work carried out in France has shown the prevalence in the elderly to be of 12.5% in males and 23.6% in women (24). By contrast, a similar study in Taiwan observed figures of 23% and 18.6%, respectively (25).
The prevalence of sarcopenia observed was 10% in men and 33% in women. Among the parameters analyzed (BMI, MM and MMI) only sex was found to be statistically different (p<0.05). We only found significant differences in BMI in the elderly group with or without sarcopenia (p< 0.05).
In our setting there are no reference values of muscle mass. Analysis of the results obtained from healthy volunteers in our population has indicated that the cut-off points to define sarcopenia are higher than in populations previously studied. This has been determined from data showing that the muscle mass in our reference population is higher. Baumgartner et al. (USA) defined reference values for muscle mass to be 7.26 Kg /m2 in men and 5.45 Kg/m2 in women while the data obtained by our group are 8.31 Kg/m2 and 6.68 Kg/m2, respectively (16).
This variation from normal values in the young population indicates the need to determine native benchmarks for establishing a correct approach to the prevalence of sarcopenia in our environment, since the use of data from other geographical areas may alter the real impact of these values.
Our results show that the prevalence of sarcopenia in healthy elderly from the community is 10% in men and 33% in women, differing from those described in other geographical areas. Such differences may be explained by various reasons, including racial differences (New Mexico and Taiwan) and the inclusion of younger subjects in the French study.
Our rates of prevalence of sarcopenia are remarkable because that they were obtained in a group of healthy elderly with preserved functional capacity, and therefore, the actual prevalence in an unselected general population and especially in elderly patients may be higher.
As recent recommended criteria for sarcopenia diagnostic are published (26), all subjects studied showed a significant decrease in muscle strength compared with a control young population, that is more marked in those with sarcopenia. Nevertheless, this fact does not translate into clinical implications.
This is the first study in our setting providing baseline data that will facilitate future studies on the prevalence of sarcopenia in various elderly populations.
One limitation of this study may be the possible bias in selection criteria among elderly patients. In addition, the participation of young subjects in the study was voluntary and may have led to a certain bias in that obese individuals tended to decline to participate. The data on the prevalence of sarcopenia obtained in this study should alert to the need for preventive measures such as nutritional and functional rehabilitation programs to thereby prevent the progression of this disease and reduce the morbidity and mortality associated with the loss of functional ability in the elderly and diminish the economic impact of the health care required by these patients. The lack of studies on the prevalence of sarcopenia in the elderly and other populations such as hospitalized patients with repeated falls emphasizes the need for future studies aimed at assessing the significance of this disease.
Study supported by
grant FIS PI050098.
Conflict of interest
The authors have no financial or any other kind of personal conflicts with this paper.
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