Influence of physical activity, sedentary lifestyle and bone biomarkers on bone health among adolescents in Kota Bharu, Kelantan

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Date
2013-05
Authors
Teo, Pey Sze
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Universiti Sains Malaysia
Abstract
Maximum attainment of peak bone mass (PBM) during the growing years is ultimately important to reduce the risk of osteoporotic fracture later in life. Understanding and identification of lifestyle factors such as physical activity (PA) and other lifestyle practices that are associated with higher bone mass accruals in children and adolescents is important in order to optimize the PBM during these critical years of growth. Therefore, the main objective of the study was to determine the influence of PA, sedentary behavioural practice and blood biomarkers of bone remodeling on bone health status, as assessed by a dual energy X-ray absorptiometry (DXA) in 455 adolescent boys and girls of Malay and Chinese-origins aged 12 to 19 years of age in Kota Bharu, Kelantan. Validated questionnaires were used to assess PA, sedentary small screen recreation (SSR) practice assessments, and dietary food intakes, whereas body composition and muscular strength of the upper and lower extremities were determined using anthropometry measurements, handgrip and isokinetic-dynamometers. For the bone health status, bone mineral content (BMC), bone area (BA) and bone mineral density (BMD) were assessed for total body (TB), at the lumbar spine (L2-L4), proximal femur and specific regions of interest using the DXA device. Mean age of the adolescents were 15.4  1.9 years, with majority (72.5%) had a normal ranges of body mass index (BMI). Sex-specific comparisons on lifestyle practices showed that adolescent boys had significantly higher levels of daily PA status (1.5hours vs. 1.0hours; P<0.001) and intense moderate-to-vigorous PA (MVPA) (1.2 vs. 0.4hours; all, P<0.001), compared to the girl participants. In contrast, sedentary SSR practices were similar between genders (3.1 vs. 3.3hours/day). In general, about two-thirds of adolescents (63.3%) had low daily active PA practice, as determined by the MVPA less than one hour per day, with higher proportion found in girls (80%) than in adolescent boys (34%). Multiple linear regression analyses showed that age (P=0.012) and sex (P<0.001) emerged as significant negative determinants on daily MVPA levels, after adjusting for ethnicity, socio-demographic status and dietary behaviours. Moreover, age (P<0.001) and daily breakfast consumption (P<0.05) emerged as negative independent determinants; whereas ethnicity (P<0.01) was significant positive independent determinant on sedentary SSR levels. The influence of these lifestyle factors was further examined based on duration spent on PA levels and sedentary SSR levels. It showed that participant boys with higher total PA group>1.5hours/day and MVPA group>1hour/day, respectively, had a significantly higher size-adjusted BMC of TB, intertrochanter and leg region (all, P<0.05) and the BMD of the TB, PF, LS, regional arm and leg region (at least, P<0.01) than that of those at low PA and MVPA levels. Only a significant positive influence was found between high total PA and MVPA with BMC and BMD of the TB and leg region in adolescent girls. Furthermore, boys with high MVPA levels showed significantly higher of muscle strength of the handgrip (P<0.01) and lower extremity strength of the quadriceps (P<0.05) and the hamstring strength (P<0.001) than those at lowest MVPA level. Only a significant positive association was found between high MVPA level and hamstring muscle strength in girls (P<0.01). On the other hand, sedentary lifestyle practices was also found to be negatively associated with bone health profiles assessed in girls, in which high SSR practice showed a significantly lower lumbar spine BMD (P<0.05) and bone area of the TB (P<0.05), arm (P<0.01) and leg region (P<0.05) compared to those who only practiced low SSR level. Blood biomarkers of bone remodeling were significantly and negatively associated with all skeletal sites assessed, after adjustments for pubertal growth and ethnicity. These present results showed that higher habitual total and intense PA level could contributed to positive bone mass profiles in these adolescents, and it has profoundly influence on weight-loaded skeletal region assessed. In addition, sedentary lifestyle practices also exert a negative influence on bone health assessed in adolescent girls. Therefore, encouragement of active lifestyle practices in children and adolescents should be promoted to optimize the peak bone mass accretion during the critical years of growth.
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Bone
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