Associations between body mass index, body composition and bone density in young adults: findings from a southern Brazilian cohort

Bierhals, Isabel Oliveira; dos Santos Vaz, Juliana; Bielemann, Renata Moraes; de Mola, Christian Loret; Barros, Fernando Celso; Gonçalves, Helen; Wehrmeister, Fernando César; Assunção, Maria Cecília Formoso

doi:10.1186/s12891-019-2656-3

Table 1 Characteristics of participants with complete data at both 18th and 22th-year follow-ups compared with those participants with missing data, loss of follow-up or death, stratified by sex

From: Associations between body mass index, body composition and bone density in young adults: findings from a southern Brazilian cohort

Variables	Men			Women
	Mean or median (SD or p25-p75); %			Mean or median (SD or p25-p75); %
	Participants included	Participants excluded¹	p-value	Participants included	Participants excluded¹	p-value
	N = 1408	N = 1195	p-value	N = 1560	N = 1085	p-value
Perinatal
Maternal education (years)	N = 1406	N = 1193	0.183^a	N = 1557	N = 1085	0.003^a
0–4	25.3	29.2		26.7	32.0
5–8	47.6	45.3		46.4	45.2
9–11	18.6	17.5		19.0	14.5
≥12	8.5	8.0		7.9	8.3
Family income (MMW)	N = 1388	N = 1159	0.039^a	N = 1528	N = 970	0.272^a
≤1	17.9	20.6		17.3	20.3
1.1–3	42.4	42.3		41.6	40.6
3.1–6	24.4	20.2		24.9	23.5
>6	15.3	16.9		16.2	15.6
Gestational age (weeks)	N = 1391	N = 1159	0.321^a	N = 1539	N = 1050	0.002^a
<34	1.2	2.0		1.2	2.9
34–36	6.2	6.4		7.8	6.7
37–40	75.8	76.1		77.2	79.3
>40	16.8	15.5		13.8	11.1
Maternal nutritional status (BMI)	N = 1366	N = 1155	0.182^a	N = 1530	N = 1046	0.237^a
Low weight	10.4	9.1		8.0	7.8
Adequate	67.3	69.7		67.6	71.3
Overweight	17.9	15.7		19.4	16.5
Obese	4.4	5.5		5.0	4.4
Birth weight (grams)	N = 1407	N = 1188	0.017^a	N = 1559	N = 1078	< 0.001^a
<2500	7.5	10.1		10.9	10.6
2500–2999	22.5	19.2		26.1	33.4
3000–3999	64.0	63.3		59.2	53.6
≥4000	6.0	7.4		3.8	2.4
Length at birth (centimeters)	N = 1395	N = 1165	0.901^b	N = 1548	N = 1054	0.029^b
Length at birth (centimeters)	49.1 (2.3)	49.1 (2.6)	0.901^b	48.5 (2.3)	48.3 (2.3)	0.029^b
15 years
Skin color	N = 1345	N = 765	0.108^a	N = 1540	N = 673	0.597^a
White	63.0	66.5		63.4	64.6
Black, brown or other	37.0	33.5		36.6	35.4
18 years
Smoking habit	N = 1408	N = 606	0.015^a	N = 1560	N = 531	0.005^a
No	86.0	81.7		88.2	83.2
Yes	14.0	18.3		11.8	16.8
Total physical activity (min/week)	N = 1406	N = 602	0.203^c	N = 1559	N = 528	0.966^c
Total physical activity (min/week)	630.0 (300.0 1110.0)	592.5 (260.0; 1140.0)	0.203^c	270.0 (110.0; 600.0)	280.0 (120.0; 600.0)	0.966^c
Total calcium consumption (mg)	N = 1406	N = 587	0.282^c	N = 1559	N = 517	0.656^c
Total calcium consumption (mg)	674.8 (488.9; 939.4)	670.6 (479.5; 897.8)	0.282^c	638.1 (449.3; 922.1)	660.2 (477.4; 891.4)	0.656^c
Lean mass index (kg/m²)	N = 1408	N = 493	0.281^b	N = 1560	N = 390	0.002^b
Lean mass index (kg/m²)	18.0 (1.5)	18.0 (1.7)	0.281^b	14.0 (1.4)	14.3 (1.6)	0.002^b
Fat mass index (kg/m²)	N = 1408	N = 493	0.012^b	N = 1560	N = 390	< 0.001^b
Fat mass index (kg/m²)	4.1 (2.9)	4.5 (3.5)	0.012^b	8.3 (3.5)	9.0 (3.9)	< 0.001^b
Body mass index (kg/m²)	N = 1408	N = 570	< 0.001^b	N = 1560	N = 449	< 0.001^b
Body mass index (kg/m²)	23.0 (3.6)	24.2 (5.5)	< 0.001^b	23.2 (4.4)	24.6 (5.8)	< 0.001^b
22 years
Lean mass index (kg/m²)	N = 1408	N = 133	0.185^b	N = 1560	N = 217	< 0.001^b
Lean mass index (kg/m²)	18.2 (1.7)	18.0 (2.0)	0.185^b	14.3 (1.7)	14.8 (1.9)	< 0.001^b
Fat mass index (kg/m²)	N = 1408	N = 133	0.571^b	N = 1560	N = 217	< 0.001^b
Fat mass index (kg/m²)	5.5 (3.4)	5.7 (4.0)	0.571^b	9.8 (4.1)	11.0 (5.0)	< 0.001^b
Body mass index (kg/m²)	N = 1408	N = 279	< 0.001^b	N = 1560	N = 315	< 0.001^b
Body mass index (kg/m²)	24.7 (4.2)	26.2 (6.7)	< 0.001^b	25.1 (5.3)	27.3 (7.3)	< 0.001^b
Whole body BMD (g/cm²)	N = 1408	N = 139	0.041^b	N = 1560	N = 221	0.532^b
Whole body BMD (g/cm²)	1.3 (0.1)	1.2 (0.1)	0.041^b	1.2 (0.1)	1.2 (0.1)	0.532^b
Lumbar spine BMD (g/cm²)	N = 1408	N = 164	0.542^b	N = 1560	N = 220	0.886^b
Lumbar spine BMD (g/cm²)	1.2 (0.1)	1.2 (0.2)	0.542^b	1.2 (0.1)	1.2 (0.1)	0.886^b
Femoral neck BMD (g/cm²)	N = 1408	N = 164	0.187^b	N = 1560	N = 220	0.355^b
Femoral neck BMD (g/cm²)	1.2 (0.2)	1.2 (0.2)	0.187^b	1.0 (0.1)	1.0 (0.1)	0.355^b
Outcome changes (Δ) at 18–22 years*
Whole body BMD change (g/cm²)	N = 1408	N = 12	0.174^c	N = 1560	N = 10	0.241^c
Whole body BMD change (g/cm²)	0.04 (0.02; 0.07)	0.04 (0.01; 0.05)	0.174^c	0.02 (0.01; 0.04)	0.04 (0.02; 0.06)	0.241^c
Lumbar spine BMD change (g/cm²)	N = 1406	N = 62	0.514^c	N = 1558	N = 32	0.980^c
Lumbar spine BMD change (g/cm²)	0.06 (0.02; 0.10)	0.05 (0.01; 0.09)	0.514^c	0.04 (0.01; 0.07)	0.04 (0.01; 0.07)	0.980^c
Femoral neck BMD change (g/cm²)	N = 1407	N = 59	0.486^c	N = 1547	N = 43	0.412^c
Femoral neck BMD change (g/cm²)	0.01 (−0.05; 0.06)	0.02 (−0.04; 0.07)	0.486^c	0.01 (−0.03; 0.05)	0.02 (−0.02; 0.10)	0.412^c

N Number of observations, SD standard deviation, % percentage, MMW monthly minimum wages, BMI body mass index, BMD bone mineral density (g/m²)
*Changes in measurement of BMD at 22y – at 18y
¹Participants excluded from the analyses due to loss of follow-up or missing data;
^aP value refers to Chi-squared heterogeneity test;
^bP value refers to Student’s t-test;
^cP value refers to Wilcoxon Rank Sum Test
The 1993 Pelotas Birth Cohort, Brazil

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