Increased fat mass and high incidence of overweight despite low body mass index in patients with spinal muscular atrophy

Abstract

Body composition is sparsely described in spinal muscular atrophy (SMA). Body (BMI, mass/height in m 2 ), fat-free (FFMI, lean mass/height in m 2 ) and fat (FMI, fat mass/height in m 2 ) mass indexes were estimated in 25 children (ages 5-18) with SMA (2 type I, 13 type II, 10 type III) using dualenergy radiograph absorptiometry and anthropometric data referenced to gender and age-matched healthy children (NHANES III, New York Pediatric Rosetta Body Project). BMI was ≥ 50 th percentile in 11 (44%) and ≥ 85 th in 5 (20%). FFMI was reduced (p<0.005) and FMI was increased (P<0.005) in the overall study cohort. FMI was ≥ 50 th , ≥ 85th and 95th percentiles in 19 (76%), 10 (40%) and 5 (20%) subjects, respectively. Using a receiver operator characteristic curve, BMI above 75 th , 50 th and 3 rd percentiles maximized sensitivity and specificity for FMI ≥ 95 th , ≥ 85 th and ≥ 50 th percentiles, respectively. Children with SMA have reduced lean and increased fat mass compared to healthy children. Obesity is a potentially important modifiable source of morbidity in SMA.

Body Composition and Chest Expansion of Type II and III Spinal Muscular Atrophy Patients

“…Higher values of body fat percentage and FMI as compared to regional normative data (paired by sex, age, and ethnic data) in the United States were also observed in 25 types I, II, and III SMA patients 11 . Another American research group 13 showed that 21 patients with types II and III SMA have higher levels of adiposity than subjects without the disease, considering either the thickness of subcutaneous fat tissue or the use of multifrequency bioelectric impedance.…”

“…The fact that these patients present low levels of physical activity due to muscle weakness and contractures reinforces the low energetic expenditure and the risk of obesity 6 . The increased fat mass represents an additional threat to the already compromised muscles that may lead to diminished motor function 11 .…”

“…The exam was performed in the supine position and the subjects received standardized recommendations: 1) no alcohol consumption or exercise within 24 hours prior to the test; 2) no caffeine or food consumption for four hours prior to the test; 3) the consumption of two-four glasses of water within the two hours prior to the test; 4) bathroom use within the 30 minutes prior to the assessment. Resistance and reactance values provided by the analyzer were used to estimate the fat-free mass (kg), in a child-specific equation 14,15 Additionally, body mass index (BMI = W/H 2 ), fat-free mass index (FFMI = FFM/H 2 ) and fat mass index (FMI = FM/H 2 ) were calculated as previously described 11 .…”

“…SMA patients present progressive symmetrical proximal weakness and hypotonia [1][2][3][4]6,8 , but there is no sensory abnormality 7 . Besides muscle weakness, respiratory 9 , orthopedic 5 , and nutritional [10][11][12] problems are particularly note wortley.…”

Prospective cohort study of spinal muscular atrophy types 2 and 3

“…Patient positioning and measurement protocols were standardized across sites as previously described. 22 The raw data were processed centrally (M.P.). Using DXA-estimated lean mass and measured height, we calculated a fat-free mass index (FFMI ϭ lean mass in kg/squared height in m 2 ).…”