Developing Functional Capacity Thresholds for Diagnosis of Sarcopenia in Africa: the multi-country MUFASSA Study

As people grow older, their bodies naturally undergo a quiet transformation. Muscles, which once powered vigorous movement, gradually lose their strength and their ability to perform daily tasks with ease. This decline is not merely a matter of feeling tired; it is a specific medical condition known as sarcopenia. It involves the loss of muscle mass and the weakening of force, leading to a higher risk of falls, fractures, and a loss of independence. For decades, doctors and researchers have tried to define exactly when this decline becomes a diagnosable condition. They have set specific numbers for how strong a person's grip should be or how fast they should walk to be considered healthy. However, these numbers were almost entirely created by studying people in wealthy, industrialized nations. The question remained: do these same numbers apply to people living in Africa, where life histories, diets, and physical environments differ significantly?

A team of researchers from universities across the United Kingdom and Africa set out to answer this question through a massive study called MUFASSA. They traveled to The Gambia, Zimbabwe, and South Africa to measure the physical capabilities of thousands of adults. Their goal was to create a new set of rules, specific to the African continent, that could accurately identify when an older person has entered the dangerous territory of sarcopenia. By testing people in their own communities rather than in hospitals, the team hoped to find a more honest picture of how aging affects muscle function in these diverse populations. The result is a new, practical way to diagnose muscle weakness that respects the unique biological and social realities of African life.

The researchers began by gathering a large and diverse group of over 5,000 adults, all aged forty or older, from urban and rural settings in three different countries. They ensured that the group included an equal number of men and women and represented a wide range of ages, from middle age to the oldest members of the community. Every participant underwent the same simple, standardized physical tests that do not require expensive machinery or complex technology. First, they measured hand grip strength by having people squeeze a handheld device as hard as they could. Next, they timed how fast the participants could walk a short distance at their normal pace. Finally, they measured how long it took for a person to stand up from a chair and sit back down five times in a row. These three tests—grip strength, walking speed, and chair rising—were chosen because they are easy to perform in any health clinic, even one with very limited resources.

To figure out what counts as "normal" and what counts as "weak," the researchers first looked at the people in their study who were between forty and forty-nine years old. They reasoned that this age group represents the peak of adult muscle function before the natural decline of older age begins. Using this healthy, younger group as a baseline, they calculated specific cut-off points for the entire continent. They determined that for men, a grip strength of less than twenty-eight kilograms indicates weakness, while for women, the threshold is less than twenty-point-three kilograms. For walking speed, the limit was set at less than half a meter per second for men and less than zero-point-four-seven meters per second for women. For the chair test, taking longer than eighteen-point-five seconds for men or twenty-one-point-five seconds for women signaled a problem. These numbers, which the team calls AFRO-SARC, were derived directly from the data collected in these three African nations, ensuring they reflect local realities rather than imported standards.

When the team applied these new African-specific rules to the entire group of older adults, they found a clearer picture of who was struggling with muscle weakness. Overall, about fourteen percent of men and sixteen percent of women had weak grip strength. Slow walking was less common, affecting about six percent of men and thirteen percent of women. However, the ability to rise from a chair showed a steeper decline with age, with nearly a third of people over seventy having difficulty with this task. When the researchers combined the signs of weak grip and slow walking to define full sarcopenia, they found that it affected roughly two to four percent of the total adult population. Among those aged seventy and older, the prevalence rose to about seven to nine percent. These numbers are lower than some previous estimates that relied on data from other parts of the world, suggesting that using foreign standards might have been overestimating the problem in Africa.

The study also confirmed that these new thresholds make medical sense. People identified as having sarcopenia using the AFRO-SARC rules were significantly more likely to have other health problems. They reported higher levels of disability, poorer overall physical performance, and lower scores on measures of healthy aging. They were also more likely to have low arm circumference, a sign of poor nutrition, and to struggle with daily activities. This strong link between the new definitions and real-world health struggles proves that the thresholds are not just random numbers, but accurate markers of a genuine health issue. The researchers noted that while the patterns of muscle decline with age looked similar to those seen in Europe and North America, the starting point for African adults was often lower. This suggests that a lifetime of different nutritional and environmental challenges may shape how muscles age, making it essential to have local standards.

One of the most important aspects of this work is its practicality. The tests used require only a simple handgrip device, a stopwatch, and a chair, making them feasible for use in remote villages and busy clinics across the continent. The researchers found that the data from The Gambia and Zimbabwe were so similar that they could be combined, while South Africa showed some differences in the chair-rising test, likely due to local variations in how the test was performed or the population's specific characteristics. By excluding the outlier data and focusing on the consistent patterns, the team created a robust set of guidelines. They concluded that adopting these African-specific thresholds will help doctors and researchers identify older adults who are at risk of losing their independence, allowing for earlier intervention and better care. This study provides the first solid foundation for understanding and treating muscle loss in Africa, ensuring that the diagnosis is as grounded in local reality as the people it aims to help.