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Risco de sarcopenia em crianças e jovens aparentemente saudáveis : implicações para o crescimento corporal e desenvolvimento físico
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Esta dissertação adotou uma abordagem integrada para analisar de que forma trajetórias de composição corporal, caracterizadas por baixa massa magra (total ou apendicular), ajustada para a estatura ou para a massa gorda (total ou do tronco), durante a infância e a adolescência, se associam ao rescimento e ao desenvolvimento físico até ao início da idade adulta. Para tal, foram conduzidos quatro estudos complementares, incluindo análises transversais e longitudinais, com períodos de seguimento entre 12 meses e 15 anos e amostras de 67 a 5.424 participantes. No primeiro estudo transversal, realizado em crianças portuguesas entre os 11–13 anos, uma maior carga metabólica relativa à capacidade (maior adiposidade acompanhada de baixa massa magra) associou-se a piores indicadores ósseos – nomeadamente menor resistência óssea na tíbia, avaliada por ultrassonografia – e a uma maturação somática mais avançada, salientando uma vulnerabilidade músculo-esquelética precoce durante o crescimento. O segundo estudo transversal utilizou uma grande amostra do National Health and Nutrition Examination Survey (NHANES), com participantes entre os 10 e os 19 anos. Os resultados sugeriram uma associação entre défices musculares estruturais (índice de massa magra apendicular ajustado à estatura – aLBMI) ou funcionais (força de preensão manual) e uma probabilidade 4 a 5 vezes superior de apresentar baixa densidade mineral óssea (DMO) do corpo inteiro sem cabeça (Whole-Body Less Head, WBLH), com maior risco nos rapazes. Por outro lado, uma menor força de preensão manual (ajustada à massa corporal) associou-se a uma maior assimetria da DMO entre membros superiores e inferiores, em ambos os sexos, embora mais pronunciada nas raparigas (probabilidade relativa 3.9 vezes superiores vs. 1.8). Estes resultados sugerem que a função muscular poderá constituir um marcador de rastreio mais informativo do que a massa muscular. Em contraste, a carga estrutural mecânica, refletida por um índice de massa magra apendicular ajustado à massa gorda do tronco (aLBM/TrFM) aumentou a probabilidade de desequilíbrio entre a DMO dos membros superiores e inferiores nos rapazes (2.4 vezes), mas não aumentou o risco de baixa DMO WBLH. 9. O terceiro estudo acompanhou 580 crianças (10–13 anos) durante 12 meses, com o objetivo de avaliar o crescimento e o desenvolvimento físico em indivíduos com risco aparente de sarcopenia. Nas raparigas, valores baixos de aLBMI ou de aLBM/TrFM associaram-se a mineralização óssea comprometida, evidenciada por um menor rácio de conteúdo mineral ósseo total/massa magra e por aumentos mais reduzidos da DMO WBLH. Nos rapazes, valores baixos de aLBMI tenderam a associar-se a menor ganho estatural. Em ambos os sexos, um fenótipo sarcopénico-like caracterizou-se por maturação somática atrasada, enquanto o fenótipo de obesidade sarcopénica-like se associou a maturação somática mais avançada. No quarto estudo longitudinal, os participantes foram selecionados do Iowa Bone Development Study (IBDS). As trajetórias de massa magra demonstraram que uma trajetória consistentemente baixa de aLBMI desde a infância até ao início da idade adulta (8–23 anos) se associou a um menor índice de massa corporal (IMC) e mineralização esquelética, incluindo uma DMO WBLH 9% inferior e uma DMO do fémur proximal 12% inferior (colo femoral e grande trocânter) e menor resistência óssea. Por sua vez, trajetórias de maior massa magra relativa à massa gorda associaram-se a diferenças ósseas modestas, mas a uma melhor densidade muscular. Globalmente, estes resultados evidenciam a importância do acompanhamento da massa e da função musculares para um crescimento e desenvolvimento saudáveis em crianças, adolescentes e jovens adultos, disponibilizando aos profissionais de saúde e investigadores uma ferramenta de avaliação relevante.
This dissertation used an integrated approach to analyse how body composition profiles characterized by low lean mass (total or appendicular), adjusted for height or fat mass (total or trunk), during childhood and adolescence are associated with growth and physical development into young adulthood. To achieve this, four complementary studies were conducted, including both cross-sectional and longitudinal analyses with follow-up periods ranging from 12 months to 15 years, and sample sizes ranging from 67 to 5,424 participants. In the first cross-sectional study, conducted with Portuguese children aged 11–13 years, a higher metabolic load relative to capacity (higher fat mass compared to low lean mass) was linked to poorer bone indicators (lower bone strength at the tibia, assessed by ultrasound) and advanced somatic maturity, emphasizing early musculoskeletal vulnerability during growth. The second cross-sectional study used a large sample from the National Health and Nutrition Examination Survey (NHANES), with participants aged 10 to 19 years. The results suggested an association between either structural (appendicular lean body mass index height-adjusted – aLBMI) or functional (handgrip strength) muscular deficits and a 4- to 5-fold higher odds of having low whole-body less head (WBLH) bone mineral density (BMD), with boys dsemonstrating a greater risk. On other hand, lower handgrip strength (adjusted for body mass) was associated with greater arms-to-legs BMD asymmetry, in both sexes, though more pronounced in girls (3.9-times higher odds vs. 1.8). This suggests that muscle function may be a more informative screening marker than muscle mass. In contrast, mechanical structural load, as indicated by a low appendicular lean body mass-to-trunk fat mass ratio (aLBM/TrFM), increased the odds of imbalance between arms and legs BMD in boys (2.4 times) but didn´t increase the risk of low WBLH BMD. The third study tracked 580 children (10–13 years old) over a 12-month period to assess growth and physical development in those at apparent risk of sarcopenia. Girls with low aLBMI or low aLBM/TrFM exhibited compromised bone mineralization, as shown by a 12 lower total BMC/lean mass ratio and smaller increases in WBLH BMD. Boys with low aLBMI tended to have less height gain. Both girls and boys with a sarcopenic-like phenotype were characterised by delayed somatic maturity, whereas those with a sarcopenic obesity-like phenotype showed advanced somatic maturity. In the fourth longitudinal study, participants were selected from the Iowa Bone Development Study (IBDS). Lean mass trajectories showed that a consistently low aLBMI trajectory from childhood to young adulthood (8–23 years) was linked to lower body mass index (BMI) an significantly reduced skeletal mineralization, including a 9% lower WBLH BMD and a 12% lower proximal femur BMD (femoral neck and trochanter) as well as lower bone strength. Conversely, higher lean mass relative to fat mass trajectories were associated with modest differences in bone outcomes but better muscle density. Overall, these results highlight the importance of tracking muscle mass and function for healthy growth and development in children, adolescents, and young adults, and provide healthcare professionals and researchers with a valuable assessment tool.
This dissertation used an integrated approach to analyse how body composition profiles characterized by low lean mass (total or appendicular), adjusted for height or fat mass (total or trunk), during childhood and adolescence are associated with growth and physical development into young adulthood. To achieve this, four complementary studies were conducted, including both cross-sectional and longitudinal analyses with follow-up periods ranging from 12 months to 15 years, and sample sizes ranging from 67 to 5,424 participants. In the first cross-sectional study, conducted with Portuguese children aged 11–13 years, a higher metabolic load relative to capacity (higher fat mass compared to low lean mass) was linked to poorer bone indicators (lower bone strength at the tibia, assessed by ultrasound) and advanced somatic maturity, emphasizing early musculoskeletal vulnerability during growth. The second cross-sectional study used a large sample from the National Health and Nutrition Examination Survey (NHANES), with participants aged 10 to 19 years. The results suggested an association between either structural (appendicular lean body mass index height-adjusted – aLBMI) or functional (handgrip strength) muscular deficits and a 4- to 5-fold higher odds of having low whole-body less head (WBLH) bone mineral density (BMD), with boys dsemonstrating a greater risk. On other hand, lower handgrip strength (adjusted for body mass) was associated with greater arms-to-legs BMD asymmetry, in both sexes, though more pronounced in girls (3.9-times higher odds vs. 1.8). This suggests that muscle function may be a more informative screening marker than muscle mass. In contrast, mechanical structural load, as indicated by a low appendicular lean body mass-to-trunk fat mass ratio (aLBM/TrFM), increased the odds of imbalance between arms and legs BMD in boys (2.4 times) but didn´t increase the risk of low WBLH BMD. The third study tracked 580 children (10–13 years old) over a 12-month period to assess growth and physical development in those at apparent risk of sarcopenia. Girls with low aLBMI or low aLBM/TrFM exhibited compromised bone mineralization, as shown by a 12 lower total BMC/lean mass ratio and smaller increases in WBLH BMD. Boys with low aLBMI tended to have less height gain. Both girls and boys with a sarcopenic-like phenotype were characterised by delayed somatic maturity, whereas those with a sarcopenic obesity-like phenotype showed advanced somatic maturity. In the fourth longitudinal study, participants were selected from the Iowa Bone Development Study (IBDS). Lean mass trajectories showed that a consistently low aLBMI trajectory from childhood to young adulthood (8–23 years) was linked to lower body mass index (BMI) an significantly reduced skeletal mineralization, including a 9% lower WBLH BMD and a 12% lower proximal femur BMD (femoral neck and trochanter) as well as lower bone strength. Conversely, higher lean mass relative to fat mass trajectories were associated with modest differences in bone outcomes but better muscle density. Overall, these results highlight the importance of tracking muscle mass and function for healthy growth and development in children, adolescents, and young adults, and provide healthcare professionals and researchers with a valuable assessment tool.
Descrição
Doutoramento em Motricidade Humana, na especialidade de Atividade Física e Saúde. Universidade de Lisboa. Faculdade de Motricidade Humana
Palavras-chave
Bone density DXA Handgrip strength Fat mass Lean mass Sarcopenia Densidade mineral óssea DXA Força de preensão manual Massa gorda Massa magra Sarcopenia