Background The excess adiposity, even in the absence of diseases, is responsible for a decline in pulmonary function, which is considered a predictor of mortality and a risk factor for diseases in several epidemiological studies. However, studies on the association between obesity and pulmonary function have found only few associations or inconclusive results. The aim of the study is to evaluate the association between body composition and spirometric parameters, comparing simple obesity measures such as body mass index (BMI) and waist circumference with more precise body composition measurements such as dual-energy X-ray absorptiometry (DXA) and air-displacement plethysmography (BOD POD). Methods This is an observational, cross-sectional study that used data from the 1978/79 Ribeirão Preto birth cohort (São Paulo, Brazil). The study included 1746 participants from the 5th follow-up of the cohort. Linear regressions were calculated to evaluate the association between BMI, waist circumference, waist–height ratio (WHtR), BOD POD- and DXA-measured fat mass percentage, and spirometric parameters FEV1, and FVC. Results For every 1-kg/m2 BMI increase, FVC decreased by 13 ml in males and by 6 ml in females and FEV1 decreased by 11 ml and 5 ml, respectively. Regarding body composition measurements, for a 1% increase in fat mass assessed by BOD POD, FVC decreased by 16 ml in males and by 8 ml in females and FEV1 decreased by 13 ml and 7 ml, respectively. Hence, negative associations between body measurements and FEV1 and FVC were observed in both genders, especially when using the fat mass measurement and were more expressive in men. Conclusion The anthropometric and body composition parameters were negatively associated with the spirometric variables FVC and FEV1. We have also observed that simple measures such as waist-height ratio were sufficient to detect the association of body composition with pulmonary function reduction.

À minha mãe, por seu apoio incondicional, por acreditar em mim e torcer pelo meu sucesso, mesmo que isso signifique estar longe, por entender que a minha ausência não depende só de mim, e que o meu gosto pelo trabalho e pelos estudos é reflexo que aprendi com ela. AGRADECIMENTOSPrimeiramente aos meus orientadores, Prof. Dr. Marco Antonio Barbieri e Prof. Dr. Elcio Vianna, que com gentileza e sabedoria me conduziram, como dois maestros, em toda essa minha caminhada. Espero ter correspondido as expectativas e tenham certeza que absorvi cada ensinamento transmitido. Eu os levarei, sempre com muito carinho, em minha jornada científica que iniciou nesse trabalho.Ao Gabriel e ao Paulo, que tiveram paciência em ficar respondendo as minhas dúvidas e as minhas solicitações, além de excelentes companhias de laboratório e almoço.À minha mãe, que aguentou meu cansaço, minha bagunça e minha ansiedade, durante todo esse processo.Aos meus irmãos, que enxergaram potencial naquela adolescente rebelde de 15 anos e a mantiveram na linha até que tudo passasse.À minha tia Alzira, que não só me apoiou durante o trabalho, como também teve que corrigir meus textos "pra ontem". Todo mundo precisa de uma ajudinha no português.Ao meu amor Cleber, que caiu de paraquedas nessa confusão e ainda teve que entrar na brincadeira, até STATA teve que conhecer. E ajuda no inglês? Também precisei. À minha família, de São Paulo e de Manaus. Pai, tios, primos, avó, que me ajudaram de tantas maneiras diferentes: caronas, marmitas, abrigo, apoio psicológico, apoio moral, paciência.Às professoras, Dra. Heloísa Bettiol e Dra. Adriana Taveira, que tornaram o MINTER uma oportunidade incrível e nos ajudaram durante o processo.Aos meus colegas do MINTER, pois, descobrimos que sofrer em grupo é mais fácil.

No abstract

Background: The excess adiposity, even in the absence of diseases, is responsible for a decline in pulmonary function, which is considered a predictor of mortality and a risk factor for diseases in several epidemiological studies. However, studies on the association between obesity and pulmonary function have found only few associations or inconclusive results. The aimed of study is evaluate the association between body composition and spirometric parameters, comparing simple obesity measures such as body mass index (BMI) and waist circumference with more precise body composition measurements such as dual-energy x-ray absorptiometry (DXA) and air-displacement plethysmography (BOD POD). Methods: This is an observational, cross-sectional study that used data from the 1978/79 Ribeirão Preto birth cohort (São Paulo, Brazil). The study included 1,746 participants from the 5th follow-up of the cohort. Linear regressions were calculated to evaluate the association between BMI, waist circumference, waist-height ratio (WHtR), BOD POD- and DXA-measured fat mass percentage, and spirometric parameters FEV1, and FVC. Results: For every 1-kg/m2 BMI increase, FVC decreased by 13 ml in males and by 6 ml in females and FEV1 decreased by 11 ml and 5 ml, respectively. Regarding body composition measurements, for a 1% increase in fat mass assessed by BOD POD, FVC decreased by 16 ml in males and by 8 ml in females and FEV1 decreased by 13 ml and 7 ml, respectively. Hence, negative associations between body measurements and FEV1 and FVC were observed in both genders, especially when using the fat mass measurement and more expressive in men. The association was detected for waist circumference.Conclusion: The anthropometric and body composition parameters were negatively associated with the spirometric variables FVC and FEV1. We have also observed that simple measures such as waist-height ratio were sufficient to detect the association of obesity with pulmonary function reduction.