Perceived Physical Fatigue and Fatigability Frequent in SMA

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by Marta Figueiredo PhD |

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The sense of physical fatigue and perceived fatigability, or the impact of reduced physical performance on daily life activities, are frequent and disabling symptoms in adults with spinal muscular atrophy (SMA) at different functional levels, a study showed.

Such symptoms — whose frequency was generally associated with motor impairment — were assessed with a newly developed SMA-specific questionnaire, which must undergo further validation before being used in the clinic or in research.

These findings support the inclusion of perceived physical fatigue and perceived fatigability in SMA-specific scales to monitor disease progression and treatment responses, the researchers noted.

The study, “Physical fatigue and perceived fatigability in adolescents and adults with spinal muscular atrophy: a pilot study,” was published in the journal Neurology Perspectives.

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SMA is characterized by the progressive loss of motor neurons, the specialized nerve cells that control voluntary movement. While muscle weakness and wasting are the most frequent symptoms, fatigue and fatigability are also commonly reported.

“Fatigue is defined as perceived mental and physical exhaustion that interferes in daily living activities,” the researchers wrote, adding that fatigability can be measured objectively by looking at reduced motor performance during daily activities.

However, these symptoms are frequently overlooked in clinics. This is due to a lack of not only standardized concepts of these symptoms, but also SMA-specific, validated tools. This lack has limited their investigation, “the development of diagnostic methods, and the implementation of specific therapies,” the researchers wrote.

The study and its findings

In this study, a team of researchers in Spain evaluated the frequency of symptoms of physical fatigue and perceived fatigability in SMA patients through a new SMA-specific, patient-reported questionnaire developed by the Spanish SMA foundation FundAME.

Perceived fatigability reflects the impact of reduced motor performance on the activities of daily living.

Physical activity questions concerned the frequency of several phenomena over the past week. These included the need to rest during the day and select activities, difficulty in maintaining posture, loss of energy throughout the day, and presence of prolonged tiredness after making a greater effort than usual.

Perceived fatigability was assessed through questions about patients’ inability to finish daily life tasks once started.

These consisted of activities requiring sustained and repeated use of the upper limbs (such as taking written notes, brushing the teeth, and eating without help), trunk and head muscles (sitting up straight and holding the head upright), and lower limbs (such as climbing a flight of stairs, walking at a steady pace, and standing up).

The study included 51 patients who completed the online questionnaire between May 1 and Nov. 30, 2020. Their median age was 27 years (range, 20–42.5 years), and their median age at symptom onset was 15.5 months (range, 11.25–33 months).

More than half (52.94%) had SMA type 2, which is characterized by the inability to stand or walk unaided, while most of the remaining patients (43.14%) had milder type 3. The severe type 1 disease and the mildest form, type 4, were the diagnosis in one patient each (1.96%).

A total of 16 patients were unable to sit without help (31.37%), 20 were able to sit unaided (39.22%), and 15 were able to walk (29.41%). Nearly half of participants (47%) reported following a specific treatment.

Results showed that 84% of patients reported some symptom of physical fatigue, with the need to select activities and energy loss over the course of the day being the most frequent (52% each).

The frequency and type of symptoms varied between functional groups, with nonsitters reporting “a greater impact of physical fatigue on daily activities,” the researchers wrote.

Sitters reported more difficulty maintaining posture than walkers, and less need to rest during the day, than the other two groups. “Walkers were the group most frequently experiencing prolonged tiredness after making a greater effort than usual,” the team wrote.

The latter is likely because patients with the greatest functional capacity more frequently perform greater efforts than usual.

These findings suggest that SMA patients’ physical fatigue is associated with both “the [motor neuron] reserve, which had previously been observed with fatigability,” and “the level of physical activity in their everyday life,” the researchers added.

Results for different functional groups

Among the three groups, nonsitters were those also reporting perceived fatigability in more daily life activities, followed by sitters and lastly by walkers.

Specifically, activities such as taking written notes, combing the hair, brushing the teeth, and eating without help, as well as sitting up straight and holding their head upright, were difficult or impossible to perform for most nonsitters.

In walkers, perceived fatigability mainly affected repetitive activities involving the lower limbs (reported by 67%–87% of patients), which the other groups were unable to perform. The most difficult task was climbing a flight of stairs (being impossible for 40% of them), and 40% also reported difficulties or inability to walk at a steady pace and to stand up.

This is consistent with data from previous studies showing that greater objective fatigability was associated with lower motor function, the team noted.

These findings highlight that “physical fatigue and perceived fatigability are frequent and disabling symptoms in patients with SMA, as they interfere with basic activities of daily living,” the researchers wrote.

As such, “these symptoms should be included in specific scales for SMA, with the aim of monitoring the overall progression of the disease,” they added.

“Future studies should address the fatigue-fatigability phenomenon from a holistic perspective to clarify its causes and the possible responses to different treatments,” the researchers wrote.

Further research is also needed to validate the questionnaire “before it can be used in research or in clinical practice,” the team wrote, adding that “the scale should also be adapted for and validated in paediatric populations, in whom these symptoms have scarcely been studied.”

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