The Expanding Role of MUAC in Adult Nutritional Assessment
While famously known as a quick screening tool for malnutrition in children under five, Mid-Upper Arm Circumference (MUAC) has a well-established and growing role in adult health, especially in vulnerable populations and resource-limited settings. Unlike Body Mass Index (BMI), which requires both weight and height, MUAC needs only a simple, non-stretchable tape measure, making it highly portable and practical. This simplicity allows for rapid nutritional screening, aiding in the identification of individuals at risk of undernutrition or chronic energy deficiency, a significant public health issue globally.
When is MUAC Preferred Over BMI?
MUAC's advantages become particularly apparent in several clinical and community scenarios where BMI measurement is challenging or unreliable. These include:
- Immobile or Bedridden Patients: For those who cannot stand to have their height and weight accurately measured, a MUAC measurement can be taken while sitting or lying down.
- Resource-Limited Settings: In remote areas or humanitarian crises where access to scales and stadiometers is limited, MUAC tapes provide a low-cost, effective alternative for large-scale nutritional screening.
- Patients with Edema: Conditions causing fluid retention (edema, ascites) can inflate body weight, leading to an inaccurate BMI. Since MUAC is less affected by fluid changes, it provides a more reliable assessment of underlying nutritional status.
- Elderly Populations: Age-related changes like decreased height and altered body composition can make BMI less representative of nutritional risk in older adults. Studies show MUAC is a reliable indicator for assessing malnutrition and frailty in this demographic.
How is MUAC Measured in Adults?
Measuring MUAC is a straightforward process that requires minimal training. The steps are as follows:
- Preparation: Ask the individual to bend their non-dominant arm at a 90-degree angle, with the upper arm parallel to the body.
- Locate Midpoint: Measure the distance between the tip of the shoulder (acromion) and the tip of the elbow (olecranon). Mark the midpoint with a pen.
- Relax and Measure: Ask the individual to relax their arm and let it hang loosely at their side. Wrap the MUAC tape around the arm at the marked midpoint, ensuring it is snug but not constricting.
- Record: Read the measurement in centimeters and record it. Different tapes may be color-coded for quick interpretation.
MUAC Cut-off Points and Interpretation
Unlike the globally recognized standards for children, universal MUAC cut-offs for adults are still under development, and many are population-specific. Research has identified various cut-off points based on correlation with BMI, with values often differing by ethnicity, age, and sex.
A 2025 study in Bangladesh, for example, found different cut-offs for younger/middle-aged versus older individuals, as well as distinct values for males and females. Research from other populations has also proposed cut-offs for identifying underweight, overweight, and obesity. It is crucial to use evidence-based cut-offs relevant to the specific population being screened for the most accurate results.
Applications in Clinical and Community Settings
MUAC's versatility makes it a valuable tool across various healthcare scenarios.
- Humanitarian Aid: During famine or emergencies, MUAC is indispensable for rapid, large-scale screening to triage severely malnourished adults for immediate intervention.
- Disease Management: For patients with chronic illnesses like HIV, tuberculosis, or chronic heart disease, MUAC provides a valuable, non-invasive way to monitor nutritional status, which is often linked to treatment outcomes and mortality.
- Maternal Health: In resource-limited settings, maternal MUAC is used to assess nutritional risk during pregnancy. A MUAC below 23cm is often associated with low birth weight and other adverse outcomes.
- Geriatric Care: In nursing homes or community-based geriatric programs, MUAC can effectively screen elderly individuals for malnutrition and frailty, providing an early warning sign for health deterioration.
Comparison: MUAC vs. BMI for Adults
| Feature | Mid-Upper Arm Circumference (MUAC) | Body Mass Index (BMI) |
|---|---|---|
| Measurement Requirements | Simple tape measure | Scale and stadiometer |
| Suitability for All Patients | Excellent for immobile, bedridden, or edematous patients | Difficult or impossible for immobile patients; inaccurate with fluid retention |
| Cost & Training | Very low cost, requires minimal training | Higher cost for equipment, requires calibrated tools and more technical skill |
| Speed | Very quick, ideal for mass screening | Slower, requires two separate measurements (height and weight) |
| Interpretive Standard | Population-specific cut-offs, no universal standard yet for adults | Internationally recognized standards (WHO), but can be misleading for certain groups (e.g., athletes) |
| Correlation with BMI | High positive correlation, demonstrates good predictive accuracy | The established gold standard for nutritional screening in many contexts |
Conclusion
In conclusion, the question, 'is MUAC used in adults?', is definitively answered with a resounding 'yes.' While its application may be less standardized than for children, MUAC is a highly practical, cost-effective, and accurate tool for assessing adult nutritional status, especially in circumstances where BMI is not feasible or reliable. Its utility across diverse populations—from those in humanitarian crises to the elderly and chronically ill—underscores its vital role in modern public health and clinical nutrition. Ongoing research and the establishment of population-specific cut-off points will continue to refine its application, solidifying MUAC's place as an indispensable screening method for adults globally.
An excellent overview of research on this topic can be found in a systematic review on PubMed Central.(https://pmc.ncbi.nlm.nih.gov/articles/PMC10200499/)
Limitations of MUAC in Adults
Despite its advantages, MUAC has limitations. It is a proxy measure and does not capture overall body composition, like fat-to-muscle ratio. Its accuracy can vary depending on factors like age, sex, and ethnicity, and it may not be as effective for screening overweight or obesity as it is for underweight. Clinicians must use MUAC as a screening tool, not a definitive diagnostic measure, and supplement it with further assessments when necessary.
