Sarcopenia

Disease Description (Causes and Symptoms)

• Definition: Sarcopenia is a condition in which muscle mass, muscle strength, and muscle function decrease due to aging and pathological factors, resulting in reduced physical function.
• Major causes
  • Insufficient intake and reduced absorption of protein (especially essential amino acids)
  • Reduced physical activity (lack of exercise)
  • Hormonal changes associated with aging (sex hormones, growth hormone, etc.)
  • Secondary factors such as chronic diseases (diabetes mellitus, chronic heart failure, chronic lung disease, chronic kidney failure), cancer, infections, and degenerative diseases (e.g., spinal stenosis)
  • Medications, dysphagia, impaired nutrient absorption, etc.
• Pathophysiology (summary): A combination of decreased protein synthesis and increased protein breakdown, atrophy of muscle fibers (especially fast-twitch fibers), inflammation, insulin resistance, and hormonal imbalance causes muscle mass and strength to decrease.
• Major symptoms
  • Abnormal gait and decreased walking speed
  • Reduced grip strength and weakness of the lower limbs
  • Fatigue and reduced ability to perform activities of daily living
  • Increased risk of falls and fractures, and reduced body weight and muscle mass
• Diagnosis (general principles)
  • Muscle strength (primary indicator): Grip strength testing (general example of cutoffs: men <27 kg, women <16 kg; criteria vary by guideline)
  • Muscle mass: Measurement of appendicular skeletal muscle mass using DXA (dual-energy X-ray absorptiometry), BIA, or CT/MRI
  • Physical function: Walking speed (low performance at ≤0.8 m/s), SPPB, 6-minute walk test, 400-meter walk test, etc.
  • Standard classifications (such as EWGSOP2) diagnose sarcopenia in the order of identifying low muscle strength → confirming muscle mass → assessing physical function.

Treatment Methods

• Basic principles: A multidisciplinary approach after evaluating the cause (nutrition, exercise, and treatment of underlying diseases)
• Exercise therapy
  • Resistance (strength) exercise is the key: at least 2–3 times per week, targeting major muscle groups, with progressive overload (initially, use low weights and high repetitions or follow physical therapy guidance)
  • Recommended example: Strength training, 2–3 sets × 8–12 repetitions, 2–3 times per week; combine with aerobic exercise (150 minutes/week at moderate intensity)
  • Physical therapy, rehabilitation therapy, and balance training to prevent falls
• Nutritional management
  • Protein target: Generally 1.0–1.2 g/kg/day for older adults, and 1.2–1.5 g/kg/day for those with sarcopenia or during recovery (adjust according to kidney function)
  • Protein per meal: To promote muscle protein synthesis, 25–30 g of high-quality protein per meal or approximately 0.4 g/kg/meal based on body weight is recommended
  • Supplementation with essential amino acids including leucine may be helpful (target approximately 2.5–3 g of leucine per meal)
  • Other: Improve nutritional status with sufficient calories, vitamin D (supplement if deficient), calcium, etc.
• Medications/supplements
  • There are currently limited approved medications that standardly treat sarcopenia. Some supplements (such as creatine 3–5 g/day) may provide benefits when combined with exercise.
  • Hormone therapy (e.g., testosterone) may be considered in selected patients with low testosterone, but benefits and risks (cardiovascular and prostate effects) must be evaluated.
  • Medications under investigation: SARMs, myostatin inhibitors, etc. (clinical trial stage).
• Other
  • Correct triggering or aggravating factors (impaired nutrient absorption, medications, depression, etc.)
  • Concurrent management of falls and osteoporosis (bone mineral density testing, environmental modifications, assistive devices)
  • Optimized management of chronic diseases (diabetes, cardiopulmonary diseases, etc.)
• Precautions and risk of complications
  • Kidney function (creatinine, GFR) should be checked when increasing protein intake
  • Consider cardiovascular risk assessment before starting exercise (such as stress testing in high-risk patients)
  • Use caution with inappropriate supplement use (excessive protein and drug interactions)
  • Complications: Loss of function, falls and fractures, worsening of chronic diseases, and increased risk of hospitalization and death

Checklist Before an Outpatient Visit (Items to Prepare and Points to Review) — Including Example Questions

• Items to prepare (recommended to submit or bring)
  • List of medications and supplements currently being taken (including dosages)
  • Previous test results (bone mineral density (DXA), body composition (BIA) results, muscle strength test results, etc.)
  • Recent records of weight changes (weight, height, BMI), and a food diary (at least 3 days recommended)
  • History of falls (within the past year) and whether a walking aid is used
  • Notes on exercise habits (type, frequency, and intensity)
  • Bring records of chronic disease diagnoses and surgical history, and recent blood test results (kidney function, liver function, blood glucose, thyroid function, vitamin D, etc.) if available
• Items that patients should record themselves before an outpatient visit
  • When symptoms began and how they have progressed (e.g., decreased walking speed and difficulties with daily activities)
  • Fatigue level, food intake and swallowing problems, and changes in appetite
  • Recent falls or fractures and the treatment received for them
• Example questions (for use during the appointment)
  • "What do you suspect is causing my current muscle weakness?"
  • "What additional tests are needed (such as muscle mass measurement or blood tests)?"
  • "What should I do regarding the recommended amount of protein intake and supplements?"

Examples of General Questions to Ask a Doctor

• "What do you think is the cause of this condition? Could another disease (e.g., thyroid disease or malnutrition) be involved?"
• "Could you explain specifically what exercise program (frequency, intensity, and type) you recommend?"
• "How much protein and which supplements (essential amino acids, leucine, creatine, etc.) should I take, and how should I take them?"
• "If medication treatment (such as hormone replacement) is needed, what are the criteria and risks?"
• "What measures are needed to reduce the risk of falls and fractures?"

Examples of Disease-Specific Questions (1–2 Appropriate to the Condition)

• "Based on my grip strength/walking speed (or DXA/BIA results), how severe is my sarcopenia? How often should I be retested?"
• "If my kidney function is impaired (or if I have diabetes or cardiovascular disease), how should the recommended protein intake or exercise plan be adjusted?"