Disability Greater in Underweight or Obese Children, Study Finds
Children with Charcot-Marie-Tooth (CMT) disease are more likely to be on either extreme of the body mass index, either underweight or obese, than their healthy peers, a large study found.
Findings also showed that among children with CMT, being underweight or obese was associated with greater disability.
The study, “Association Between Body Mass Index and Disability in Children With Charcot-Marie-Tooth Disease,” was published in the journal Neurology.
Studies have shown that body mass index (BMI), a measure of weight in relation to height, influences body functionality in both healthy children and those with neuromuscular disorders.
BMI is a widely used indicator of body fat, with reference values developed according to age, sex, and ethnicity. It allows clinicians to predict disease risk among children and adolescents, and is currently used as part of health and growth assessments in children.
Healthy children with higher BMI values, indicative of being overweight, have greater fat infiltration into their muscles, poorer balance and walking, increased pressure on their feet, and reduced bone strength, all of which can influence normal body functioning and quality of life.
Excess body fat, muscle wasting, and fatty infiltration of the muscles are all issues faced by children with a neuromuscular disease. And children with CMT are known to be less active than their healthy peers, which may play a role in maintaining a healthy BMI.
Numerous studies have shown that excessive weight in children with neuromuscular conditions, such as Duchenne muscular dystrophy or spinal muscular atrophy, further impairs mobility and muscle mass. However, few studies have looked into underweight pediatric patients, or specifically at children with CMT.
Researchers assessed 477 children and adolescents, ages 3 to 20, with CMT who were recruited as part of the Inherited Neuropathy Consortium from 2009 through 2015 at sites in Australia, Italy, England, and the U.S. These patients were age- and sex-matched to 316 healthy children from the 1,000 Norms Project, a project that established reference values for functional, demographic, and body composition factors.
Among the children with CMT, 45.1% were between the ages of 3 and 10, while 54.9% were between the ages of 11 and 20.
By CMT type, most of the patients (55.6%) had CMT1A, followed by 4.6% having CMT2A, 2.5% with CMT4C, 2.3% having CMT1B, and 2.1% with CMTX1.
The overall BMI distribution differed between CMT and control groups, with a higher proportion of CMT children being severely underweight, underweight, or obese than healthy children. However, no differences in BMI distribution were found according to age or sex in either group.
A greater proportion of severely underweight, underweight, and obese was seen in those with CMT1A, similar to the overall CMT group.
However, compared while CMT1A patients, a greater proportion of those with CMT2A and CMT4C were severely underweight or underweight, while those with CMT1B were more commonly underweight, and participants with CMTX1 were more frequently overweight or obese.
“The main finding of this large international study … was a 3-fold higher frequency of children who were severely underweight and underweight and a 2-fold increase in the prevalence of obesity among the CMT cohort compared to age- and sex-matched healthy children,” the scientists wrote.
The researchers also scored the patients according to the CMT Pediatric Scale (CMTPedS), a way of assessing disability, in which a higher score (up to 44) is indicative of greater disability and a score of 0 reflects an unaffected child.
CMTPedS scores differed according to BMI groups, with those who were severely underweight having a mean score of 27.2, underweight patients a mean score of 20.2, and those with a healthy weight a score of 16.8. Children who were overweight had a mean score of 17.3, and obese patients of 21.3.
Compared to CMT patients with healthy weight, being severely underweight or obese — having a more extreme BMI — was associated with increased disability.
Notably, the researchers suggested that, in overweight children and adolescents, the increased load on weakened muscles combined with a sedentary lifestyle may contribute to a greater disability.
Compared with CMT patients of healthy weight, those who were severely underweight had poorer 6-minute walk test score (an assessment of exercise capacity), decreased ability to point the foot downward, lesser grip strength, gait impairment, and reduced finger dexterity and sensation.
Grip strength in particular could be predictive of malnutrition in children, the researchers noted, as it is an indicator of poorer physical function in adults with malnutrition.
Obese CMT patients showed a poorer performance on the 9-hole peg test of finger dexterity and the 6-minute walk test than did healthy weight patients.
None of the CMT patients scored 0 on the CMTPedS test, indicative of some degree of impairment.
Mean CMTPedS scores among severely underweight or healthy weight children were higher, indicating greater disability, in children with more severe forms of CMT — CMT2A and CMT4C — as compared to the overall CMT group.
Self-reported symptoms varied across the weight groups, with overweight and obese children reporting more frequent foot pain. Obese patients also reported more frequent leg cramps, while those who were severely underweight reported tripping, falling, tingling and burning more often.
“If an unhealthy BMI is found to be associated with disease progression, then interventional studies will be needed to determine whether maintaining a BMI in the healthy range through better nutritional strategies and exercise can decrease the rate of CMT progression,” the investigators wrote.
“We recommend that families and clinicians aim for a BMI that targets a healthy weight range as opposed to being on the extreme ends of weight for age where disease severity is increased,” they added.