O baixo peso ao nascer está associado ao menor conteúdo mineral ósseo na vida adulta? resultados do Estudo Longitudinal de Saúde de Adulto (ELSA-Brasil)

Abstract

INTRODUCTION: Low birth weight, a marker of intrauterine growth, seems to be related to the lower accumulation of bone mineral content (BMC) during life. However, this relationship is not yet fully understood. OBJECTIVE: To investigate the association between birth weight and BMC, after adjustment for body size, and whether this relationship is different between men and women, and also adulthood and elderlies participants of the Longitudinal Study of Adult Health (ELSA-Brasil). METHODS: 10,499 participants from the second wave of exams and interviews (2012-2014) from ELSA-Brasil were eligible for this analysis. ELSA-Brasil is a multicenter cohort composed of 15,105 active or retired civil servants, aged 35 to 74 years, from six higher education and research institutions located in six capitals (Belo Horizonte, Porto Alegre, Rio de Janeiro, Salvador, São Paulo and Vitória). The outcome variable was the amount of bone mineral content in kilograms determined by a vertical direct segmental multifrequency electrical bioimpedance fixture (InBody 230). The explanatory variable of interest was low self-reported birth weight, dichotomized as no and yes (<2.5 kg). The magnitudes of the associations were estimated by means of mean differences and their respective 95% confidence intervals using linear regression. All analyzes were stratified by sex and sequential adjustments were made as follows: crude model (Model 1); by age, self-reported race / color and educational attainment (Model 2); physical activity and alcohol consumption (Model 3); presence of diabetes, antidiuretic use, and menopausal status for women (Model 4); and current weight and height (Model 5). In order to confirm the presence of sex and age effect modification in the association between birth weight and bone mineral content in adulthood, the interactions terms were included in the final model (Model 5) considering the total study population (birth weight*sex) and stratified by sex (birth weight*age). Analyzes were performed using Stata 13.0. RESULTS: Most were women (54.86%), and the average age was 55 years (SD = men ± 8.98; women ± 8.54). Those who self-reported low birth weight was associated with lower amounts of bone mineral content, (mean difference for men: -0.28; 95%CI: -0.34; -0.21 / mean difference for women: -0.14; 95%CI: -0.18; -0.10) when compared to those of adequate birth weight. By adding adjustments for socioeconomic characteristics, health behaviors and conditions, no significant changes in the magnitude of the associations were observed (Men: -0.23; 95%CI: -0.29; -0.17; Women: -0, 14; 95%CI: -0.18; -0.10). However, when adjusting for current weight and height, there was a considerable reduction in the magnitude of the associations (Men: -0.04; 95%CI: -0.06; -0.01, Women: -0.01%; 95%CI: -0.03; -0.00). The presence sex effect modification was found in the association of low birth weight with BMC, but without age effect modification. CONCLUSION: Low weight seems to influence bone mineral content; however, part of this relationship is mediated by current height and weight. In addition, we found a change in the effect of LBW on BMC according to sex.