PEAK BONE MASS ATTAINMENT IN MALAYSIAN CHILDREN: INFLUENCE OF DIET, LIFESTYLE PATTERNS, VITAMIN D STATUS AND MATERNAL INTERACTIONS

Abstract

Background: While bone health disorder commonly begins from childhood, its preventive measures do not receive enough attention and is seldom a priority in the national health goals in Malaysia. Studies have shown that a mere improvement of 10% in peak bone mass (PBM) during childhood will halve the risk of an osteoporotic fracture in adult life. Modifiable lifestyle factors and body composition can affect the attainment of PBM during childhood. However, limited Asian studies are examining the association of modifiable factors with bone mineral density (BMD) attainment in pre-adolescent children. Furthermore, it is widely reported that Malaysian children have a habitually low calcium intake and a high prevalence of vitamin D deficiency. Therefore, this study performed a cross-sectional analysis of the determinants of bone health among pre-adolescent Malaysian children. The main hypothesis is calcium intake, physical activity, vitamin D status and maternal interactions are associated with BMD among pre-adolescent Malaysian children. Methods: A total of 243 pre-adolescent children (aged 8-11 years) and 163 premenopausal mother-child pairs were included in the study. For children, the body composition, bone mineral content (BMC) and BMD at the lumbar spine (LS) and total body (TB) were measured by dual-energy X-ray absorptiometry (DXA) using Lunar GE iDXA. Dietary intakes were estimated using 1-week diet history while physical activity level (MET score, metabolic equivalent score) and sun exposure index was determined using validated questionnaires. Serum vitamin D (25(OH)D) was analysed using liquid chromatography Tandem Mass Spectrometer (LC-MS/MS). Mothers’ BMC and BMD at the lumbar spine were also measured using DXA. Maternal calcium and vitamin D intake were estimated using validated food frequency questionnaires (FFQs). Mother’s physical activity level (MET, metabolic equivalent) and sun exposure index were also determined using validated questionnaires. Knowledge, attitude and perceived behaviour (KAP) towards calcium intake of the mothers were determined using an adapted questionnaire. Statistical analyses were performed using the Statistical Package for Social Science (SPSS) statistical software (Version 25, SPSS Inc., Chicago, IL, US). The data were checked for normality (Kolmogorov-Smirnov). Descriptive statistics (mean, standard deviation, median, interquartile range, frequency and percentage) were reported for sociodemographic characteristics, medical history, anthropometry, bone parameters blood biomarker, dietary intake, physical activity and sun exposure indexes as well as the scores of adult knowledge, attitude and perceived behaviour toward calcium intakes. The comparison between sex for continuous variables was analysed using independent T-test for parametric data, whereas the Mann-Whitney U test was used for non-parametric data. The comparison between groups for continuous variables was analysed using ANOVA for parametric data. Bivariate correlation or partial correlation (r) between lifestyle factors and bone parameters were performed using Pearson’s correlation. Correlation between non-parametric variables was tested using Spearman correlation. Stepwise multiple linear regressions were performed to determine the association between lifestyle factors and bone parameters among children and mother-child pairs. Results: Boys had higher TBBMC (boys: 1160.4 ± 237.9g vs girls: 1095.6 ± 220.5g, p = 0.029) and TBBMD (boys: 0.780 ± 0.075g/cm2 vs girls: 0.754 ± 0.072g/cm2, p = 0.029) than girls. No children were identified as ‘low bone mass’ and mean Z-scores for BMD in boys was 0.890 ± 0.921 and in girls was 0.678 ± 0.994. No significant differences were observed at TB bone area, TBBMD Z-score as well as measurements at total body less head (TBLH) and LS. Dietary calcium (boys: 356 ± 167mg/day vs girls: 342 ± 194 mg/day, p > 0.05) and vitamin D intakes (boys: 1.5 ± 1.6μg/day vs girls = 1.4 ± 1.6μg/day, p > 0.05) were lower than Malaysian recommended nutrient intake (RNI) in both sexes. Girls had significantly lower physical activity level (boys: 961 ± 502mins/week vs girls: 670 ± 317mins/week, p < 0.001), serum 25(OH)D (boys: 20.1 ± 5.5ng/mL vs girls:14.7 ± 4.8ng/mL, p < 0.001), and sun index (boys: 1.49 ± 0.78 vs girls: 0.09 ± 0.05, p < 0.001), compared to boys. Among the mothers, their mean age was 40.3 ± 5.9 years. The mean LSBMD for mothers (mLSBMD) were 1.191 ± 0.145 g/cm2 and 18 mothers (11%) were classified as osteopenia. No osteoporotic adult was identified in this study. The calcium intake for mothers was low at 534 ± 305mg/day compared to recommended intake level. The mothers had a low-moderate physical activity level (1724 ± 1905mins/week) and the mean sun index of 0.51. The mothers were found to have a reasonable level of knowledge about calcium consumption (mean knowledge score of 10.3 out of 17). Nevertheless, they demonstrated a positive attitude towards the importance of calcium intake (mean attitude score of 4.2 out of 5). Stepwise analysis showed that FM (p = 0.011), SI (p = 0.006) and BSA*Gender (p < 0.001) were significantly associated with serum 25(OH)D. Among the boys, LM was the strongest significant predictor of LSBMD (β=0.607, p<0.001) and TBBMD (β=0.481, p<0.01). Other significant predictors for boys’ bone health were height, fat mass, physical activity level. Similar to boys, among girls, LM was the strongest significant predictor of LSBMD (β=0.700, p<0.001) and TBBMD (β=0.747, p<0.001). Other significant predictors for girls’ bone health were calcium intake, height and fat mass. After adjusted for age, weight, height and dietary calcium intake, a positive correlation was detectable in bone traits for mother-children pairs. The maternal descent had determined 21.4 – 27.8% of bone traits (TBBMD and LSBMD) in boys whereas 31.8 – 34.4% of bone traits in girls. However, no association was found between maternal KAP toward calcium intake with children’s dietary intakes. Conclusion: The study finding suggests that children whose parents have low bone density should focus on modifiable risk factors (e.g. improving children’s LM) to optimize peak bone mass for osteoporosis prevention in their children. Encouraging physical activity while promoting calcium intake and a balanced diet that builds on lean body mass should be the focus when developing public health guidance to promote bone health status amongst Malaysian children. The prevalence of insufficiency in serum 25(OH)D was high among the children. Encourage outdoor activity and prolonged sunlight exposure to improve serum 25(OH)D is important to ensure healthy bone status among children and adults.