Impact of physical activity, anthropometric, body composition and dietary factors on bone stiffness in German university students.

BACKGROUND Bone density in the young-adult life is associated with risk for osteoporosis in later life. Next to genetic factors, lifestyle seems to play an important role for bone health. Purpose of the study was to clarify the relationship between various lifestyle factors and bone parameters in university students. METHODS In 233 women and 52 men (age: 22.7±3.1 vs. 24.0±3.2 years; BMI: 22.2±2.9 vs. 24.2±3.1 kg∙m-2) the following parameters were assessed: calcaneal stiffness index (SI; quantitative ultrasound), body composition (bioelectrical impedance analysis), actual and past physical activity level (PAL; standardized questionnaire), and food/nutrient intake (3-day dietary record). Sex differences (Mann-Whitney-U-tests), relationships between SI and lifestyle factors (Spearman´s rank correlation), and the influence of the factors on the variance of SI (multiple linear regression) were tested (α=0.05). RESULTS 6.9% of the women and 5.8% of the men were classified as osteopenic (-2.5 0.05). In multiple regression analysis physical activity during adolescence, actual PAL, and BMI explained 8% of the variance of SI (p<0.0001): SI=32.2+3.5∙physical activity during adolescence [1=very low, 2=low, 3=medium, 4=high, 5=very high]+28.5∙PAL+0.8∙BMI [kg∙m-2]). CONCLUSIONS Parameters of physical activity seem to be more important for bone health than nutrition factors. Therefore, high levels of physical activity during childhood, adolescence, and early-adult life are highly recommended to improve bone parameters.