Abstract
Objectives
Sarcopenia is a debilitating condition affecting millions of individuals worldwide and is defined with different criteria. The objective of this study was to determine the prevalence of sarcopenia in older Canadians using three internationally accepted criteria.
Design
Observational cohort study.
Settings and participants
Data from 12,592 subjects [6,314 males (50.1%), 6,278 females (49.9%)] ≥65 years old in the Canadian Longitudinal Study on Aging were included. Measurements: Appendicular lean mass (ALM; kg) and appendicular lean mass index (ALM kg/height in m2) were collected from dual X-ray absorptiometry measurements. Physical performance was assessed using the 4-m gait speed test, and muscle strength was measured by hand dynamometry. Sarcopenia was defined according to criteria put forth by the International Working Group on Sarcopenia (IWGS), Foundation for the National Institutes of Health (FNIH) Sarcopenia Project, and revised European Working Group on Sarcopenia in Older People (EWGSOP). Positive and negative percent agreements and Cohen's kappa (κ) described the agreement among sarcopenia definitions.
Results
Among the evaluated criteria, gait speed ≤ 1.0 m/s (IWGS definition of slowness) was the most frequently identified deficit (56.8% males, 57.2% females). The prevalence of sarcopenia ranged from 1.4 to 5.2% in males and 1.6 to 7.2 % in females among the different definitions. Positive percent agreement values among criteria were generally low (range: 1.5–55.3%) and corresponded to κ indicating none to minimal agreement (0.01–0.23). Negative percent agreement values were ≥ 95%.
Conclusion
Sarcopenia prevalence was relatively low in older Canadian adults and current definitions had poor agreement in diagnosing individuals as sarcopenic.
Key words: Body composition, physical function, physical performance, muscle function, strength
Introduction
Approximately one in six Canadians (16.9%) is 65 years of age or older (1) and this number is expected to grow up to 23.6% by 2030 (2). This demographic is particularly susceptible to accelerated and progressive skeletal muscle loss. When low skeletal muscle occurs alongside other symptoms such as low physical performance and/or weakness in older adults, it is termed “sarcopenia”. This condition is associated with significant adverse consequences, such as increased health care costs, loss of independence, physical disability, hospitalization, falls, fractures and frailty (3, 4, 5, 6).
Currently, there is lack of unanimity over consensus criteria for identifying sarcopenia. Different operational criteria for sarcopenia have been proposed by different working groups, which is an obstacle to understanding the true burden of this condition in older adults (7, 8, 9). Determining the prevalence of sarcopenia is highly dependent on the methodological approach, diagnostic criteria, and population of interest, and prevalence ranging from 10 to 40% worldwide have been previously reported (10). However, the extent of such results truly attributable to real differences among populations (instead of the well-known influence of the adopted criteria over the prevalence estimates) remains unknown.
Defining the prevalence of sarcopenia within each geographic region is a vital first step in creating a “global map” of this condition (11), and, to date, there are no Canadian estimates of the condition available. Therefore, the main objective of study was to determine the prevalence of sarcopenia in older Canadians using three of the most frequently adopted operational definitions: the ones proposed by the International Working Group on Sarcopenia (IWGS) (9), Foundation for the National Institutes of Health (FNIH) (10), and revised European Working Group of Sarcopenia in Older Persons (EWGSOP2) (8). Secondarily, we also sought to determine the agreement among these definitions.
Methods
Study Population
The Canadian Longitudinal Study on Aging (CLSA) is a multi-center cohort including a nationally stratified random sample of community-dwelling Canadian adults aged 45 to 85 years old. The study design and further details of the CLSA has been previously described elsewhere (12, 13), but, briefly, study participants were selected among individuals living within a 25-kilometer radius of a data collection site (located in Vancouver, Victoria [British Columbia], Calgary [Alberta], Winnipeg [Manitoba], Hamilton, Ottawa [Ontario], Montreal, Sherbrooke [Quebec], Halifax [Nova Scotia] and St. John's [Newfoundland]). Data used in the present analysis includes baseline data for males and females ≥65 years of age who were part of the in-depth cohort of the CLSA that included individuals who completed a physical examination component (as opposed to telephone interview only).
Participants' Characteristics
Participants provided sociodemographic data on age, sex, smoking status, marital status and education level during an in-person interview. Subjects were also asked the ethnic or cultural background of their ancestors. The following responses were considered in our classification of Caucasian ethnicity: Canadian, French, English, German, Scottish, Irish, Italian, Ukrainian, Dutch, Hebrew, Polish, Norwegian, Welsh, or Swedish. All other ethnicities were considered non-Caucasian.
Anthropometric and Body Composition Assessments
Weight, height, waist circumference and hip circumference were measured using standard procedures during a visit to the data collection site, after removal of shoes, headwear, and excess layers of clothing. Height was obtained using a stadiometer (Seca 213, Seca GmbH & Co.; Hamburg, Germany) to the nearest 0.1 centimeter and body weight was measured with a digital scale (140-10 Digital Physician Scale, Healthweigh; Halesowen, United Kingdom). The average of two measures of height and weight were used. Body mass index (BMI; kg/m2) was calculated from measured weight and height and classified according to the World Health Organization cut-points for adults (underweight: <18.5 kg/m2; normal weight: 18.5–24.9 kg/m2; overweight: 25–29.9 kg/m2; obese: ≥30.0 kg/m2) (14). Waist circumference was collected in the horizontal plane around the position of the natural indent in the waist area, halfway between the last rib and the iliac crest. Hip circumference was taken at the point of greatest horizontal circumference of the hips and buttocks. Both measurements were recorded to the nearest 0.1 cm.
Next, body composition was assessed using whole-body examinations by dual-energy X-ray absorptiometry (DXA; Discovery A™, Hologic; Marlborough, Massachusetts, United States). The sum of lean soft tissue in both arms and legs was used as a measure of appendicular lean mass (ALM; kg) and appendicular lean mass index (ALMI; ALM [kg]/squared height [m2]) was calculated from this value. Fat mass (kg) and percent fat mass (fat mass [kg]/body weight [kg] × 100) were also used to characterize the study population.
Physical Performance and Strength
A 4-metre gait speed test was conducted to evaluate physical performance. Participants completed one practice trial before the recorded test. Subjects were instructed to walk as fast as possible, without running, through a pre-determined 4-metre straight path marked on the floor, and the time taken to complete the course was recorded using a validated stopwatch. Speed was then calculated as the 4-m length of the path divided by the elapsed time to complete the test (m/s).
Handgrip strength was measured using a digital grip dynamometer (Tracker Freedom JTECH Medical; Midvale, Utah, United States). Participants sat in a straight-backed chair with feet on the floor and upper arms close to the body with elbow of dominant hand flexed at 90 degrees. Following a practice maximal squeeze of the dynamometer, participants completed three maximal squeezes with 15 seconds in between each trial. The highest measure from the dominant hand was used.
Definitions of Sarcopenia
Sarcopenia was defined and classified using the criteria proposed by IWGS (8), FNIH (9), and EWGSOP2 (2018 version, with updated definitions for females from erratum) (7), as presented in Supplemental Table 1. Low muscle mass cut-offs were based on ALMI (IWGS and EWGSOP2) or ALM adjusted for BMI (FNIH). Low muscle function cut-offs were based on gait speed and/or grip strength. Severe sarcopenia was also identified within FNIH and EWGSOP2 diagnostic schema. Although the EWGSOP2 definition also included a definition for probable sarcopenia, this was not included in our primary analyses since low muscle weakness alone is defined as' dynapenia' rather than sarcopenia (15, 16).
Table 1.
Anthropometrics and body composition of older adults
| Males | Females | |||||||
|---|---|---|---|---|---|---|---|---|
| ≥65 yr | 65–69.9 yr | 70–79.9 yr | ≥80 yr | ≥65 yr | 65–69.9 yr | 70–79.9 yr | ≥80 yr | |
| Anthropometrics | ||||||||
| Weight, kg | 84.5 ± 14.5 | 87.4 ± 15.4 | 84.0 ± 14.1 | 90.3 ±12.2 | 71.1 ± 14.8 | 73.0 ± 15.9 | 71.0 ± 14.3 | 67.4 ± 13.1 |
| N | 6317 | 2113 | 3175 | 1029 | 6237 | 2184 | 3045 | 1044 |
| Height, cm | 173.8 ± 6.9 | 174.8 ± 6.7 | 173.7 ± 6.9 | 172.3 ± 6.6 | 159.7 ± 6.3 | 160.6 ± 6.3 | 159.8 ± 6.3 | 157.9 ± 6.2 |
| N | 6318 | 2114 | 3173 | 1031 | 6278 | 2186 | 3048 | 1043 |
| Waist circumference, cm | 101.2 ± 11.9 | 101.8 ± 12.6 | 101.0 ± 11.8 | 100.3 ± 10.8 | 89.6 ± 13.3 | 89.9 ± 14.2 | 89.7 ± 13.0 | 88.7 ± 12.4 |
| N | 6279 | 2095 | 3161 | 1023 | 6256 | 2178 | 3038 | 1040 |
| Hip circumference, cm | 103.1 ±9.5 | 103.5 ± 10.0 | 103.0 ± 9.3 | 102.9 ± 9.0 | 105.9 ± 12.1 | 106.5 ± 12.7 | 105.9 ± 12.0 | 104.4 ± 11.0 |
| N | 6279 | 2095 | 3161 | 1023 | 6256 | 2178 | 3038 | 1040 |
| Waisthip ratio | 0.98 ±0.06 | 0.98 ± 0.06 | 0.98 ± 0.06 | 0.98 ± 0.06 | 0.84 ± 0.07 | 0.84 ±0.07 | 0.85 ± 0.07 | 0.85 ± 0.07 |
| N | 6279 | 2095 | 3161 | 1023 | 6256 | 2178 | 3038 | 1040 |
| BMI, kg/m2 | 27.9 ± 5.7 | 28.6 ± 4.6 | 27.8 ± 4.2 | 27.0 ± 3.8 | 28.0 ± 4.3 | 28.3 ±6.1 | 27.8 ± 5.5 | 27.0 ±5.1 |
| N | 6314 | 2113 | 3172 | 1029 | 6271 | 2184 | 3045 | 1042 |
| BMI Class, N (%) | ||||||||
| Underweight | 22 (0.4) | 5 (0.2) | 13 (0.4) | 4 (0.4) | 84(1.3) | 29(1.3) | 38(1.3) | 17(1.6) |
| Normal weight | 1536 (24.3) | 448 (21.2) | 788 (24.9) | 300 (29.2) | 1998 (31.9) | 661 (30.3) | 951 (31.2) | 386 (37.0) |
| Overweight | 3063 (48.5) | 985(46.6) | 1545 (48.7) | 533 (51.8) | 2334 (37.2) | 790 (36.2) | 1164 (38.2) | 380 (36.5) |
| Obese | 1693 (26.8) | 675 (32.0) | 826 (26.0) | 192 (18.6) | 1855 (29.6) | 704 (32.2) | 892 (29.3) | 259 (24.9) |
| Physical Function | ||||||||
| Handgrip strength, kg | 37.3 ± 8.7 | 40.3 ± 8.5 | 36.9 ± 8.0 | 32.0 ± 7.3 | 22.2 ± 5.2 | 24.1 ±5.0 | 21.9 ±4.9 | 19.0 ±4.5 |
| N | 5893 | 1995 | 2969 | 929 | 5331 | 1923 | 2716 | 892 |
| Walk speed, m/s | 0.98 ± 0.20 | 0.98 ± 0.20 | 0.98 ± 0.20 | 0.98 ± 0.20 | 0.97 ± 0.20 | 0.98 ± 0.20 | 0.97 ± 0.20 | 0.98 ± 0.20 |
| N | 6260 | 2098 | 3114 | 1018 | 6221 | 2165 | 3016 | 1040 |
| Body Composition | ||||||||
| ALM, kg | 25.9 ± 3.9 | 27.1 ±3.9 | 25.6 ± 3.7 | 24.0 ± 3.3 | 17.4 ±3.0 | 17.9 ±3.1 | 17.3 ±3.0 | 16.4 ±2.7 |
| N | 6031 | 2017 | 3046 | 968 | 5920 | 2088 | 2875 | 957 |
| ALMI, kg/m2 | 8.6 ± 1.1 | 8.9 ± 1.1 | 8.5 ± 1.0 | 8.1 ± 1.0 | 6.8 ± 1.1 | 6.9 ± 1.1 | 6.8 ± 1.0 | 6.5 ± 1.0 |
| N | 6031 | 2017 | 3046 | 968 | 5920 | 2088 | 2875 | 957 |
| 20th percentile ALMI | 7.54 | 7.87 | 7.53 | 7.22 | 5.82 | 5.92 | 5.83 | 5.64 |
| N | 6031 | 2017 | 3046 | 968 | 5920 | 2088 | 2875 | 957 |
| ALM/BMI | 0.93 ±0.13 | 0.96 ±0.13 | 0.93 ± 0.12 | 0.90 ± 0.12 | 0.63 ±0.10 | 0.64 ±0.10 | 0.63 ±0.10 | 0.62 ±0.10 |
| N | 6027 | 2016 | 3045 | 966 | 5917 | 2088 | 2875 | 957 |
ALM: appendicular lean mass; ALMI: appendicular lean mass index; BMI: body mass index
Data Analysis
All data were analyzed for males and females separately, because of the inherent differences in body composition between sexes. Continuous variables were assessed for normality using the Anderson-Darling Normality test. Differences in proportions between groups of individuals (i.e. male versus female or by age group) was assessed using Chi-Square. Positive percent agreement was defined as the proportion of participants categorized as having sarcopenia by two criteria (analogous to a sensitivity calculation) and negative percent agreement was defined as the proportion of participants who were categorized as not having sarcopenia by two criteria (analogous to specificity). For comparability, agreement was assessed among definitions of sarcopenia (from all three criteria) and between FNIH and EWGSOP2 severe sarcopenia. Only participants with all diagnostic criteria measures (i.e. body composition, muscle performance) were included in sarcopenia prevalence calculations. Two-sided p-values with significance levels set at 0.05 for hypotheses testing were reported. Analysis were performed using the statistical software R, version R-3.2.1 (R Foundation for Statistical Computing; Vienna, Austria).
Results
Study Population Characteristics
Data was available for a total of 12,592 individuals 65 years of age or older, of which 6,314 (50.1%) were males, and 6,278 (49.9%), were females (Table 1). Of those, Participants were primarily Caucasian (93%), never smokers (89%), married or in a common law union (84%) and had a bachelor's degree or higher (51%). Most participants had a BMI in the overweight (n=5397, 42.9%) or obese (n=3548, 28.2%) categories with very few in the underweight category (n=106,0.8%).
Prevalence of Sarcopenia
Within the entire sample, 11,797 adults had sufficient data for the IWGS definition (gait speed and ALMI), 10,727 had data for the FNIH definition (grip strength, gait speed, ALMI and BMI) and 10,733 had data for the EWGSOP2 definition (grip strength, gait speed, and ALMI). In males, prevalence of individual components of sarcopenia diagnosis criteria ranged from 5.8% (low ALMI, according to EWGSOP2 cut-offs) to 56.8% (slow gait speed, as defined by IGWS), Table 2. Among females, such values ranged from 8.2% (low ALMI, defined by EWGSOP2) to 57.2% (slow gait speed, according to IWGS definitions).
Table 2.
Gait speed, grip strength, and muscle mass of a population representative sample of older Canadians by sex
| Prevalence (%) | ||||||
|---|---|---|---|---|---|---|
| Variables | Classification | Cut-points | N(%) | Males N=6260 | Females N=6221 | P |
| Gait Speed – FNIH & EWGSOP2 | Normal | >0.8 m/s | 10410 (83.4) | 83.6 | 83.2 | 0.57 |
| Low | ≤0.8 m/s | 2071 (16.6) | 16.4 | 16.8 | 0.57 | |
| Gait Speed – IWGS | Normal | >1.0 m/s | 5364 (43.0) | 43.2 | 42.8 | 0.67 |
| Low | ≤1.0 m/s | 7117 (57.0) | 56.8 | 57.2 | 0.67 | |
| Grip Strength – FNIH | Normal | M≥26 kg | ||||
| F≥16 kg | 10303 (90.2) | 91.6 | 88.7 | <0.001 | ||
| Low | M<26 kg | |||||
| F<16 kg | 1121 (9.8) | 8.4 | 11.3 | <0.001 | ||
| Grip Strength – EWGSOP2 | Normal | M≥27 kg | ||||
| F≥16kg | 10189 (89.2) | 89.6 | 88.7 | 0.12 | ||
| Low | M<27 kg | |||||
| F<16 kg | 1235 (10.8) | 10.4 | 11.3 | 0.12 | ||
| ALMI – IWGS | Normal | M>7.23 kg/m2 | ||||
| F>5.67 kg/m2 | 10654 (89.2) | 90.7 | 87.6 | <0.001 | ||
| Low | M≤7.23 kg/m2 | |||||
| F≤5.67 kg/m2 | 1297 (10.8) | 9.3 | 12.4 | <0.001 | ||
| ALMI- EWGSOP2 | Normal | M>7.0 kg/m2 | ||||
| F>5.5 kg/m2 | 10265 (85.9) | 94.2 | 91.8 | <0.001 | ||
| Low | M≤7.0 kg/m2 | |||||
| F≤5.5 kg/m2 | 1686 (14.1) | 5.8 | 8.2 | <0.001 | ||
| ALM/BMI | Normal | M≥0.789 | ||||
| F≥0.512 | 10721 (89.8) | 88.4 | 91.1 | <0.001 | ||
| Low | M<0.789 | |||||
| F<0.512 | 1223 (10.2) | 11.6 | 8.9 | <0.001 | ||
ALM: appendicular lean mass; ALMI: appendicular lean mass index; BMI: body mass index; EWGSOP2: European Working; Group on Sarcopenia in Older People; IWG: International Working Group on Sarcopenia; FNIH: Foundation for the National; Institutes of Health, p-value obtained using Chi square for differences in proportion between males and females
Among definitions, the prevalence of sarcopenia ranged from 0.2% (EWGSOP2) to 5.2% (IWGS) in males, and from 0.2% (EWGSOP2) to 7.2% (IWGS) in females with all age groups combined, Table 3. The prevalence of severe sarcopenia using FNIH criteria was slightly higher than the prevalence of severe sarcopenia as defined by EWGSOP2 criteria in both sexes (FNIH: 2.0% in males, 1.9% in females; EWGSOP2: 1.2% in males, 1.3% in females). Classification using the IWGS sarcopenia definition had the highest prevalence (males: 5.2%; females: 7.2%). The prevalence of severe sarcopenia was also higher than the prevalence of sarcopenia according to the FNIH and EWGSOP2 definitions. Most definitions of sarcopenia (including severe sarcopenia) increased with age in both males and females, Figure 1A and 1B; the exception was FNIH and EWGSOP2 definitions of sarcopenia in males in which a slight decrease in prevalence was observed from age 70–79 to ≥ 80 years (FNIH: 0.64%, 70–79 years, 0.58% ≥ 80 years; EWGSOP2 0.35% 70–79 years, 0.12% ≥ 80 years).
Table 3.
Prevalence of sarcopenia according to different diagnostic criteria in older Canadians
| Males | Females | ||||
|---|---|---|---|---|---|
| N | % | N | % | ||
| IWGS, n=11, 797 | |||||
| No sarcopenia | Adequate walk speed and muscle | 5,647 | 94.8 | 5,423 | 92.8 |
| Sarcopenia | Slowness + low muscle | 308 | 5.2 | 419 | 7.2 |
| FNIH, n=10,727 | |||||
| No sarcopenia or severe sarcopenia | Adequate strength and muscle | 5,434 | 97.5 | 5,045 | 97.9 |
| Sarcopenia | Weakness + low muscle | 25 | 0.5 | 10 | 0.2 |
| Severe sarcopenia | Weakness + low muscle + slowness | 113 | 2.0 | 100 | 1.9 |
| EWGSOP2, n=10,733 | |||||
| No sarcopenia or severe sarcopenia | Adequate strength and muscle | 5,497 | 98.6 | 5,077 | 98.5 |
| Sarcopenia | Weakness + low muscle | 11 | 0.2 | 12 | 0.2 |
| Severe sarcopenia | Weakness + low muscle + slowness | 67 | 1.2 | 69 | 1.3 |
EWGSOP2: revised European Working Group on Sarcopenia in Older People; IWG: International Working Group on Sarcopenia; FNIH: Foundation for the National Institutes of Health
Figure 1.
Prevalence of sarcopenia across age groups in males (A) and females (B)
EWGSOP2: Revised European Working Group on Sarcopenia in Older People; IWGS: International Working Group on Sarcopenia. FNIH: Foundation for the National Institutes of Health Sarcopenia Project.
Agreement among Operational Definitions
Percent agreement statistics among definitions are presented in Table 4. Negative and positive percent agreement values were commonly higher in males compared to females. Positive percent agreement values were generally low (range: 0.3–33.3%), with the exception of IWGS and EWGSOP2 definitions of sarcopenia which had 100% agreement in males and females. All negative percent agreement values were ≥ 95%.
Table 4.
Agreement among sarcopenia criteria in older Canadians
| IWGS sarcopenia | EWGSOP2 Sarcopenia | EWGSOP2 Severe Sarcopenia | ||||
|---|---|---|---|---|---|---|
| PPA (%) | NPA (%) | PPA (%) | NPA (%) | PPA (%) | NPA (%) | |
| Males | ||||||
| FNIH sarcopenia | 1.2 | 99.8 | 214 | 99.8 | - | - |
| IWGS sarcopenia | - | - | 100 | 96.8 | - | - |
| FNIH severe sarcopenia | - | - | - | - | 33.3 | 99.2 |
| Females | ||||||
| FNIH sarcopenia | 0.3 | 99.9 | 77 | 99.9 | - | - |
| IWGS sarcopenia | - | - | 100 | 95.2 | - | - |
| FNIH severe sarcopenia | - | - | - | - | 22.2 | 99.2 |
EWGSOP2: revised European Working Group on Sarcopenia in Older People; IWG: International Working; Group on Sarcopenia; FNIH: Foundation for the National Institutes of Health; NPA: negative; percent agreement; PPA: positive percent agreement
Discussion
This investigation assessed the prevalence of sarcopenia according to different criteria in a representative population of non-institutionalized community-dwelling older Canadian adults. Our results revealed an overall low prevalence of sarcopenia in the entire sample and when categorized according to age. Most operational criteria also had poor agreement in detecting sarcopenia. These findings raise important questions regarding the identification and, consequently, treatment of sarcopenia in older adults.
Although the term ‘sarcopenia' was originally used to describe muscle wasting in older individuals (17), this condition is currently associated with impairments not only related to muscle mass, but function as well (that is, strength and/or performance). Although low muscle mass alone has been demonstrated as sufficient to predict clinical outcomes in several different populations (18), skeletal muscle without consideration of physical performance or strength may not adequately categorize individuals as sarcopenic within geriatric populations. For example, McLean et al. (19) investigated the likelihood for mobility impairment (gait speed ≤ 0.8 m/s) among 6,280 adults aged ≥ 65 years over a 10-year follow-up. Low grip strength (in absolute values and adjusted for BMI) and ALM/BMI were associated with mobility impairments, while absolute values of ALM were not associated with the odds of developing “slowness”. Among those classified as being weak, the odds of developing mobility impairment were similar for those with and without low ALM, suggesting that strength may be a more effective predictor of future mobility-related issues than muscle mass (19). Each individual aspect of these criteria may not necessarily be proportionally correlated, but, instead, represent different aspects of the aging process (20, 21). This is exemplified in our data by the high prevalence of slow gait speed and relatively less common occurrence of low skeletal muscle quantity or handgrip strength. In fact, gait speed ≤ 1.0 m/s was the most common physical detriment among both males and females. Furthermore, the prevalence of severe sarcopenia (weakness, low muscle mass, and slowness) was higher than sarcopenia (weakness and low muscle mass with normal gait speed) across age groups using FNIH and EWGSOP2 definitions. This suggests that slow gait speed and low strength often simultaneously accompany low muscle mass in older adults. Gait speed may therefore represent a clinically viable tool to identify those at risk for poorer outcomes compared to measures of muscularity alone (22, 23).
Similarly, low handgrip strength occurred in 8.4–11.3% of participants in the present analysis. Previous studies have suggested that handgrip weakness is related to poor quality of life, physical limitations, longer hospital stays, and shorter survival (24, 25, 26); it is also more easily accessible in clinical settings than other tests of physical performance. These advantages are reflected in the updated EWGSOP2 guidelines which recommend using strength tests to assess the probability of sarcopenia along with body composition and physical performance assessments to confirm diagnosis and determine sarcopenia severity, respectively. However, since muscle weakness is not concordant with the occurrence of low muscle quantity and each disorder relates to unique pathophysiology and heath outcomes (15, 16, 27), muscle weakness alone is considered dynapenia rather than sarcopenia. The present analysis therefore compared only definitions of sarcopenia and severe sarcopenia rather than weakness alone, as defined by the EWGSOP2 definition of ‘probable sarcopenia'.
Using the evaluated operational definitions put forth by consensus groups, sarcopenia prevalence within our sample was low - ranging from 0.2 to 5.2% in males and 0.2 to 7.2% in females - and generally occurred at similar rates between sexes. These values are similar to those reported in an analysis of 10,063 participants ≥65 years of age with various ethnicities, wherein sarcopenia occurrence using FNIH criteria was 1.3% and 2.3% for males and females, respectively; IWGS-defined sarcopenia was slightly higher in this cohort, with 5.1% of males and 11.8% of women considered sarcopenic (28). However, other studies have reported different values of sarcopenia prevalence. For example, among healthy elderly Europeans, no individuals had sarcopenia according to IWGS and 0.6% had sarcopenia using FNIH (29). Also, our prevalence results are substantially lower than those reported in a recent systematic review and meta-analysis of the prevalence of sarcopenia in community-dwelling adults ≥ 55 years (10), wherein a pooled prevalence of 9.9% using IWGS (95% CI: 3.2–16.6%) and 18.6 % using FNIH (95% CI: 11.8–25.5%) were reported. This discrepancy between our data and the metaanalysis could be due to the range of sarcopenia definitions included within each classification for the pooled analysis (10), potentially artificially inflating the apparent prevalence of sarcopenia.
Notably, the revised EWGSOP2 definition assesses muscle performance as a severity criterion instead of a diagnostic criterion. In practical terms, this produces lower sarcopenia prevalence estimates than the original 2010 definition (30). Because the revised EWGSOP2 criteria were recently published, there are limited analyses on the prevalence of sarcopenia in population-representative samples, although some investigations have suggested EWGSOP2 results in lower sarcopenia prevalence compared to the original EWGSOP criteria (31, 32, 33). Nevertheless, the prevalence of sarcopenia and severe sarcopenia according to EWGSOP2 appear to be lower in the CLSA cohort compared to other studies in community-dwelling older adults in the Korean Frailty and Aging Cohort Study (34) or octogenarian community-dwelling men (35), but similar to older individuals from Ireland (36). Variance in reported sarcopenia rates using EWGSOP2 therefore likely reflect differences in body composition among race and ethnicities (37), although there is insufficient data to support consensus sarcopenia definitions according to broad ethnicity categories.
We observed an overall low positive percent agreements and high negative percent agreements among definitions, suggesting poor case-finding agreement. Such discrepancies may be partially explained by the different adjustments to muscle mass values adopted by each definition. FNIH criteria adjusts ALMI by body size and stature (BMI), which considers the metabolic load of excess body weight. Other criteria (7, 8) use ALM adjusted for height squared, which does not quantify muscularity in relation to adiposity. Considering low muscle mass in the context of excess fat mass is especially relevant given the high prevalence of overweight and obesity. In fact, approximately 70% of older adults in our sample have overweight or obesity, which is similar to estimates within the Canadian population (38). In addition, even small variations in cut-points can substantially impact the reported occurrence of sarcopenia. For example, differences of ≤0.23 kg/m2 in EWGSOP2 and IWGS cut-points resulted in prevalence of low ALMI ranging from 5.8 to 9.3% in males and 8.2 to 12.4%, respectively. It is also important to note that these values may be partially due to low prevalence of sarcopenia within the cohort. Small numbers of a condition are inherently related to high variation in positive percent agreement values; low prevalence may also contribute to high negative percent agreement values.
Inconsistency among sarcopenia definitions may have considerable implications within clinical practice. In 2016, sarcopenia was officially recognized as a medical condition and received its own International Statistical Classification of Diseases and Related Health Problems-10 (ICD-10) code. However, the lack of unified consensus on the best method to identify this condition may impede adoption of this code into clinical practice. Understanding the most suitable definition for a given population and outcome of interest is important for determining the impact of sarcopenia. In fact, identifying sarcopenia is a key component of recommendations for managing sarcopenia (39). Determining the most suitable definition for a given population (i.e. the one that is associated with a significant increase in the risk of incapacity or frailty) is important for investigating its impact on other outcomes of interest, as exemplified in a recent publication using the CLSA dataset (40). Of note, definitions should also aim to balance sensitivity and specificity to ensure reasonable accuracy while saving healthcare resources (by avoiding over-diagnosis of sarcopenia).
Although this is the largest investigation to estimate sarcopenia prevalence among older Canadians, some inherent limitations should be considered. Our sample was composed of relatively healthy community-dwelling older adults, and our findings may not be applicable to clinical populations. Also, the CLSA investigation did not directly ask participants to describe their ethnicity, and it is known that body composition may differ among ethnicities. We assumed parental cultural background to be a valid surrogate for ethnicity, acknowledging that cultural and phenotypical ethnicity may characterize subjects differently. The proportion of Caucasians in this sample was therefore only used as a part of the descriptive analysis, although future research should conduct sensitivity analysis to assess variability in sarcopenia estimates across ethnicities.
In conclusion, community-dwelling older Canadians have an overall low prevalence of sarcopenia. However, there was poor congruity among the evaluated definitions of sarcopenia, which could impede the translation of these criteria to clinical practice. Further research should characterize the prevalence and most appropriate definition of sarcopenia on a global scale to facilitate improved preventative and treatment strategies for this condition.
Author contributions
Study concept and design: ID, MS, CMP. Acquisition of data: CMP. Analysis and interpretation of data: All authors. Drafting of the manuscript: MM and SAP. Critical revision of the manuscript for important intellectual content: All authors.
Funding
This work (specifically, data from the CLSA) was supported by the Government of Canada through the Canadian Institutes of Health Research (CIHR) under grant reference: LSA 9447 and the Canada Foundation for Innovation. The CLSA is led by Drs. Parminder Raina, Christina Wolfson and Susan Kirkland. This work was also supported by a CIHR Catalyst Grant FRN 151279. C. M. Prado is supported by a Canadian Institutes of Health Research (CIHR) New Investigator Salary Award and the Campus Alberta Innovates Program.
Ethical standards
This investigation was approved by the Research Ethics Office at the University of Alberta (Study ID Pro00070975). All participants provided written informed consent and data were de-identified before analyses by the study team.
Conflicts of interest
The authors have no conflicts of interests to declare.
Electronic supplementary material
Supplementary material is available for this article at https://doi.org/10.1007/s12603-020-1427-z and is accessible for authorized users.
Supplemental Table 1. Definitions of sarcopenia from different criteria
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Supplementary Materials
Supplemental Table 1. Definitions of sarcopenia from different criteria