A discussion of statistical methods to characterize early growth and its impact on bone mineral content later in childhood

Background Many statistical methods are available to model longitudinal growth data and relate derived summary measures to later outcomes. Aim To apply and compare commonly used methods to a realistic scenario including pre- and postnatal data, missing data and confounders. Subjects and methods Data were collected from 753 offspring in the Southampton Women’s Survey with measurements of bone mineral content (BMC) at age 6 years. Ultrasound measures included crown-rump length (11 weeks’ gestation) and femur length (19 and 34 weeks’ gestation); postnatally, infant length (birth, 6 and 12 months) and height (2 and 3 years) were measured. A residual growth model, two-stage multilevel linear spline model, joint multilevel linear spline model, SITAR and a growth mixture model were used to relate growth to 6-year BMC. Results Results from the residual growth, two-stage and joint multilevel linear spline models were most comparable: an increase in length at all ages was positively associated with BMC, the strongest association being with later growth. Both SITAR and the growth mixture model demonstrated that length was positively associated with BMC. Conclusions Similarities and differences in results from a variety of analytic strategies need to be understood in the context of each statistical methodology

Additional file 1: Table S1. of Association of maternal diabetes/glycosuria and pre-pregnancy body mass index with offspring indicators of non-alcoholic fatty liver disease

Univariable associations of maternal diabetes status, by maternal existing diabetes, gestational diabetes and glycosuria compared to no diabetes/glycosuria with offspring USS and blood-based markers of non-alcoholic fatty liver disease. Table S2. Results of the multivariable model (model 4) of the association of maternal diabetes/glycosuria with offspring USS determined fatty liver. Table S3. Results of the multivariable model (model 4) of the association of maternal pre-pregnancy obesity status and BMI with offspring USS determined fatty liver. Table S4. Multivariable associations (model 4, with adjustment for offspring concurrent BMI) of maternal diabetes/glycosuria with offspring USS and blood-based markers of non-alcoholic fatty liver disease. (N = 1,215 or 2,358 as indicated). Table S5. Multivariable associations of maternal pre-pregnancy BMI ((model 4, with adjustment for offspring concurrent BMI)) with offspring USS and blood-based markers of non-alcoholic fatty liver disease. (N = 1,215 or 2,358 as indicated). (DOCX 26 kb

Additional file 1: of Association of parents’ and children’s physical activity and sedentary time in Year 4 (8–9) and change between Year 1 (5–6) and Year 4: a longitudinal study

Table S1. Mean difference (95% confidence interval) in the children’s average sedentary minutes per day in Year 4 associated with parents’ sedentary time in Year 4 and Year 1 for those with complete data. Table S2. Mean difference (95% confidence interval) in the children’s average moderate-to-vigorous physical activity minutes per day in Year 4 associated with parents’ moderate-to-vigorous physical activity in Year 4 and Year 1 for those with complete data. Table S3. Mean difference (95% confidence interval) in the children’s change in sedentary minutes per day between Year 1 and Year 4 associated with parents’ change in sedentary time between Year 1 and Year 4 for those with complete data. Table S4. Mean difference (95% confidence interval) in the children’s change in moderate-to-vigorous physical activity minutes per day between Year 1 and Year 4 associated with parents’ change in moderate-to-vigorous physical activity between Year 1 and Year 4 for those with complete data. (DOCX 25 kb

Cross-sectional and prospective associations of BMI with blood pressure at age 9 years in the multiple imputation data.

<p>Cross-sectional and prospective associations of BMI with blood pressure at age 9 years in the multiple imputation data.</p

Characteristics of children who participated in the study only at age 9 years and those who participated at both ages 6 and 9 years in the observed and multiple imputation datasets.

<p>Characteristics of children who participated in the study only at age 9 years and those who participated at both ages 6 and 9 years in the observed and multiple imputation datasets.</p

Cross-sectional and prospective associations of BMI with hypertension at age 9 years in the multiple imputation data.

<p>Cross-sectional and prospective associations of BMI with hypertension at age 9 years in the multiple imputation data.</p

Cross-sectional associations of physical activity with blood pressure at age 9 years in the multiple imputation data (N = 1223)*.

<p>Cross-sectional associations of physical activity with blood pressure at age 9 years in the multiple imputation data (N = 1223)*.</p