Prevalence of Sarcopenia in Elderly Population

Abstract

Background: Sarcopenia refers to aged related loss of skeletal muscle mass and physical function. It leads to not only adverse health outcome but also increased healthcare expenditure. Studies indicated that smoking, insufficient nutrition, physical inactivity, older age, gender, reduction in motor unit number and atrophy of muscle fibers are contributing factors to sarcopenia. Indeed, sarcopenia is usually found in elderly population. There is no universal definition for sarcopenia. Diagnosis of sarcopenia, according to different definition criteria, requires complex instruments and participation of professionals. Recently, a simple questionnaire SARC-F has been developed to screening out sarcopenia.

Objective: The project has three objectives: to estimate the prevalence of sarcopenia among aged 65 and over elderly in community setting using SARC-F; to explore the distribution of SARC-F scores among different age group population; to compare the prevalence of sarcopenia in Hong Kong with those in other countries.

Study design: This is a cross-sectional study.

Setting: Residential care homes (hostel for the elderly, home for the aged, care and attention home and nursing home) in Shatin district.

Method: A self-design questionnaire including demographic information, smoking habit, alcohol intake, chronic diseases, hospitalization events and SARC-F will be assessed face to face when the participants are enrolled.

Background

Sarcopenia is age related disease with symptoms of loss of muscle mass, strength and function. Elderly over the age of 65 years are vulnerable to sarcopenia ^[6]. It is estimated that approximated 5-13% of older people aged 60–70 years are suffered from sarcopenia ^[8]. The proportion is about twice higher among elderly at the age of 80 or above ^[8]. Studies also found that sarcopenia is more likely seen in older men than older women ^[16,26]. Sarcopenia gains intensive attention from public and increasing researches indicated that it is a major clinical problem for older people.

Risk factors of sarcopenia

Current research found that lifestyle factors, including physical inactivity, smoking and alcohol consuming ^[3]; and biological factors, including older age, gender, decreased hormone level, motor unit remodeling and reduced protein synthesis ^[3,25], contribute to development of sarcopenia.

Motor unit remodeling comes up of age and leads to replacement of fast twitch motor neuron^[22,25] which results in less precise control of movements, less force production and slowing of muscle mechanics^[22,23,25] as remodeled motor unit are smaller in size and slower to contract. Therefore, loss of fast twitch fibers increases risk of having sarcopenia.

In addition, protein synthesis, growth hormone (GH), testosterone (T) and insulin-like growth factor (IGF-1) are considered to be associated with sarcopenia as well ^[25]. It is well known that protein is important in muscle repairmen. And GH, T and IGF-1 are involved in protein metabolism and maintenance ^[23]. Different studies agreed that protein synthesis rate decreases throughout the natural aging process ^[24] and leads to loss of muscle mass. Thus, low protein synthesis rate, along with decrease in these hormones level provide possible occurrence of sarcopenia ^[25].

Consequences of sarcopenia

Sarcopenia causes serious consequences not only at individual level but also at societal level. On the one hand, loss of muscle mass, strength and function lead to adverse health outcome in terms of frailty, disability, morbidity and mortality ^[8]. Essentially, sarcopenia is about twice as common as frailty ^[9]. Also, sarcopenia occurs with other morbidity in some times. Some of the co-morbidity are obesity ^[4,13], hypertension, osteoporosis ^[12] and type II diabetes ^[5,14,15]. Moreover, research suggests that loss of skeletal muscle strength may predict future mortality in middle-aged and elderly ^[2]. On the other hand, sarcopenia is linked with increased healthcare expenditure. In United States, the estimated direct healthcare attributable to sarcopenia represented about 1.5% of total healthcare expenditure in 2000 ^[21].

Diagnosis of sarcopenia according to different consensus panels

Although research working in the area of sarcopenia is expanding exponentially, a universal definition is still under development. On average, current definitions are including muscle mass, muscle strength or even physical function.

In 2010, the European Working Group on Sarcopenia in Older People (EWGSOP) published guidelines to help identify sarcopenia ^[1,9]. According to the EWGSOP, a person will be classified as having sarcopenia when two of three follow criteria were statisfied: (A) low muscle mass and (B) low muscle strength and/or (C) low physical performance ^[1]. Low muscle mass is defined as muscle mass ≥2 standard deviations below the mean of reference population ^[8], calculating by equipment such as DEXA-scanners. Low physical performance is defined as gait speed ≤ 0.8 m/s in the 4 meters walk test for both males and females ^[8].

International Working Group on Sarcopenia (IWGS) suggested diagnosing sarcopenia when the following criteria are fulfilled: (a) gait speed was < 1 m/s and (b) low muscle mass (cutoff value is similar to EWGSOP) ^[8].

The European Society of Parenteral and Enteral Nutrition Special Interest Groups carried out that the cut off values for low muscle mass is defined as percentage of muscle mass > 2 SDs below the mean of reference individuals; for walking speed is < 0.8 m/s in the 4 meters walk test ^[1].

Measurement of muscle mass and muscle strength

Muscle strength is mainly assessed by handgrip ^[8]. While physical performance can be measured using simple tests such as the short physical performance battery test, usual gait speed or the timed get-up-and-go test ^[8]; it is difficult to assess muscle mass in practice. Dual-energy X-ray absorptiometry (DEXA) is recently proposed as the gold standard for muscle mass measurement ^[8]. Other methods include bioelectrical impedance, computed tomography, magnetic resonance imaging, urinary excretion of creatinine, anthropometric assessments, and neutron activation assessments can be used for measurement of muscle mass as well ^[8]. The process is complicated and need participation of professionals. Prevalence of sarcopenia varies as use of cut-off points relies on different instruments used for assessing muscle mass and strength and function.

SARC-F questionnaire

SARC-F, a newly developed simple questionnaire, has been regarded as rapid diagnosis test for sarcopenia. It contains five components: strength, assistance in walking, rise from a chair, climb stairs and falls ^[7]. A question will be asked to assess each component variable. Scores range from 0-10, with 0-2 for each component ^[7]. Participants with total score higher than 4 are classified as having sarcopenia. Details of SARC-F are shown in table 1.

Table 1 SARC-F screen for sarcopenia

A research conducted in Hong Kong tests the validation of SARC-F as a screening tool for sarcopenia in community. It found that SARC-F is able to predict future adverse outcomes with comparable power to other criteria. It also found that SARC-F has excellent specificity (94.4%) and negative predictive value but poor sensitivity. With high specificity, SARC-F is useful for screening out older adults with sarcopenia. Poor sensitivity may due to the number of participants classified as having sarcopenia represent only a small proportion of the total population studied ^[10]. Poor sensitivity may implicate that participants have mild symptoms cannot meet the threshold of criteria or only few person in this community have sarcopenia.

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Another research conducted in mainland China applied SARC-F to screening sarcopenia and physical disability. It published that poor physical performance and grip strength were associated with SARC-F defined sarcopenia. But there was a very weak correlation to muscle mass in physically active outpatients. It carried out potential explanation that the weak correlation may partly due to only small sample measured by DXA or BIA ^[11].

Problem Identification and Definition of Task

Although it is well known that sarcopenia is related to various serious consequences mentioned above, many gaps remain and new horizons need future study. While researches consistently suggest that resistance strength training helps prevent sarcopenia, few studies point out that gym exercise and home exercise intervention is less useful for elderly population ^[21]. Estimation of prevalence is important to find out different contributing factors to sarcopenia and explore cost-effective healthcare intervention to reduce occurrence of sarcopenia. However, it is difficult to assess muscle mass due to lack of equipment or human resource. Therefore, this project will use a simple questionnaire containing five questions to screening out elderly with sarcopenia in Hong Kong community.

Relevance to Public Health

Sarcopenia is coming of age. Elderly population is expected to remain on a rising trend in most of developed countries. In Hong Kong the proportion of the population aged 65 and over is projected to rise markedly from 13% in 2012 to 30% in 2041. It means that increasing population will suffer from sarcopenia.

It is not surprise that sarcopenia increase the risk of physical disability. The risk of disability is 1.5 to 4.6 times higher in older persons with sarcopenia than in older persons with normal muscle. Men are at greater risk of sarcopenia related disability than women ^[16]. Recent estimates indicate that approximately 45% of the older U.S. population is sarcopenic and that approximately 20% of the older U.S. population is functionally disabled ^[21]. It is important to note that physical disability is associated with an increased risk of nursing home placement, home healthcare and hospital use ^[21]. And these healthcare services need extra healthcare expenditure to support. To sum up with information above, sarcopenia is becoming big challenge in public along with the rise of older population. It is cause serious health consequences in persons and make economic burden in countries.

Setting

There are 21 license residential care homes in Shatin district. Residential care services for elders aim to provide residential care and facilities for elders aged 65 or above who, for personal, social, health and/or other reasons, cannot adequately be taken care of at home.

To meet different care needs of elders, range level of care from low to high, residential care home is category into four types: hostel for the elderly, home for the aged, care and attention home and nursing home.

Project timeline

Below is the timeline of my project. Data collection and data analysis will be done in March and April respectively.

Figure 1 Project timeline

Aim and Objective

The overall aim of this capstone project is to apply SARC-F questionnaire in Hong Kong population. The three specific objectives are showed below:

1. To estimate the prevalence of sarcopenia among aged 65 and over elderly in community setting using SARC-F;
2. To explore the distribution of SARC-F scores among different age group population;
3. To compare the prevalence of sarcopenia in Hong Kong with those in other countries.

Method

This is a cross-sectional study. Participants who are enrolled in this project will be categorized into two groups (with sarcopenia and without sarcopenia) by SARC-F. Those with total score of higher than four are classified as having sarcopenia.

Sample size calculation

For population of 20000, at a confidence level of 95% and 5% margin of error, with 50% response distribution, the calculated sample size is 377.

Data collection

Sampling frame is all old women and men at the age of 65 and over in residential care homes. Elderly who is consent to participate will be recruited. We exclude those who (1) had a bilateral hip replacement; (2) were not competent to give informed consent; (3) suffering from acute exacerbation of any disease or acute pain.

Recruit subject population using cluster sampling as name list of sampling frame is not available. A self-design questionnaire including demographic information, smoking habit, alcohol intake, chronic diseases, hospitalization events and SARC-F will be assessed face to face when the participants are enrolled. To make the interview more comprehensive and affluent, two or more questions will be assessed each component variable in SARC-F. Details are shown in the table below:

Table 2 Variables of SARC-F for sarcopenia

According to the table, strength will be measured by questions: do you find it difficult if you were to lift up a ten-pound object (such as a bag of rice) up from the floor? If the answer is yes, participants will be asked one more question: how much difficulty do you have doing this? Variables for strength measurement are answer of this question: some difficulty, much difficulty or unable to do. Assistance in walking will be assessed by three questions: do you have any difficulties walking 2 to 3 blocks outside on level ground? If the answer is yes, participants will be asked another question: how much difficult do you have doing this? Variables for this component measurement are answer of this question: some difficulty, much difficulty or unable to do. An extra question is: do you use walking aids, such as a cane? Rise from a chair will be measured by one question: could the participant stand up one time unassisted? Option includes stands without using arms, unable to stand, rises using arms and did not attempt or refused. Climb stairs will be measured by two questions: do you have any difficulties climbing up 10 steps without resting? If the answer is yes, participants will be asked: how much difficult do you have doing this? Option includes some difficulty, much difficulty or unable to do. The last component falls will be measured by questions: in the past 12 months, have you fallen and landed on the floor, or fallen and hit an object like a table or a chair? If the answer is yes, participants will be asked: how many times have you fallen in the past 12 months? Option includes once to three times or four times and above.

Statistics analysis

Predictive variables include demographics (age, gender), lifestyle (smoker/non-smoker, alcohol intake) and chronic diseases (obesity, hypertension, osteoporosis, type II diabetes). Smokers are classified by having ever smoked more than 5 packs of cigarettes in the past. Drinkers are classified by having consumed more than 5 units of alcohol per day ever. To measure above predictive variables, several questions will be assessed to each participant. Details as following:

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Smoking – Do you have ever smoked more than 5 packs of cigarettes per day in the past? Participants are categorized as smoker if the answer is yes. Alcohol consuming – Do you have ever consumed more than 5 units of alcohol per day?, Participants are classified as drinker if the answer is yes. Chronic disease history – Do you have any chronic diseases (e.g. hypertension, type II diabetes, heart disease, obesity)?

Potential confounders include age and gender. To adjust effect of confounders, subgroup analysis will be done in groups of women and men within different age group (65-69, 70-74, >= 75).

Outcome variables are sarcopenia and hospitalization event. Sarcopenia is measured by SARC-F questionnaire. The cut-off score is four. Hospitalization events in the past two years from the enrolling day were verified will be counted.

Examine using logistic regression the bivariate associations between sarcopenia and obesity, diabetes, smoking and alcohol use.

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