<p>Osteoporosis is a major worldwide public health problem through its association with fragility fracture. Acquisition of peak bone mass (PBM) is an important contributor to later osteoporosis risk and may be modified by lifestyle factors, including habitual recreational sporting activity (HRSA). Previous studies that have considered the relationship between HRSA and bone health have focused on older people, elite sporting activity and used dual energy X-ray absorptiometry as a measure of bone density, rather than calcaneal quantitative ultrasound (cQUS), the outcome measure in this study. This research is important because it considers younger adults, to determine relationships between HRSA and bone health in adolescents and young adults, and the factors that affect their engagement with HRSA. In this thesis we consider the relationship between HRSA and bone health in three separate studies, reported as four manuscripts: (1) a systematic literature review of studies that considered relationships between non-elite sporting activity and bone health in adolescents and young adults as assessed by calcaneal heel ultrasound; (2) a quantitative study of 452 adolescents and young adults aged 16 to 35 years, who completed a questionnaire detailing sporting activity and relevant lifestyle confounders and underwent heel ultrasound measurements; and (3) nine focus groups of young adults to better understand their knowledge of bone health, the factors that impact it, and the barriers and facilitators to increasing HRSA. The results of the systematic literature review suggested that the available literature was scarce, with few studies focusing on relationships between HRSA and cQUS in adolescents and young adults. The studies available were too heterogeneous to perform a meta-analysis although, through a narrative synthesis, we reported that all six studies included in the systematic literature review reported significant benefits from weight-bearing HRSA on cQUS outcomes. In the quantitative study, selected bone cQUS parameters were positively associated with: BMI (SI- stiffness index, BUA-broadband ultrasound attenuation, and T-score); physical activity (SI, SOS-speed of sound, BUA, and T-score); and past HRSA score (SOS only), with weight-bearing sporting activity such as running (SI and SOS), soccer (SI and BUA) and rugby (T-score and Z-score) associated with better bone health. This study also reported that lifetime sport participation typically declined after individuals’ mid-teens. The qualitative study suggested that knowledge of PBM and risk of osteoporotic fracture were limited in the young adult age group. There was a general awareness of the positive and negative impacts of many lifestyle behaviours such as physical activity, diet, tobacco smoking and alcohol consumption on health in general, but not specifically how these impact PBM and good bone health in later life. Furthermore three main barriers to sports participation that emerged were: a) structural (disorientation in a new living environment, facilities, access to healthcare); b) social (financial and time constraints); and c) personal (social pressures and lack of an understanding of why sporting activity matters for bone health). On the other hand, enablers of sports participation included: a) supportive environments; b) access to health checks including support to avoid injury; and c) education to better understand the benefits of HRSA. In conclusion, HRSA that is of higher impact appears to be associated with more favourable bone health as assessed by heel ultrasound, but few studies have adequately considered these relationships. The quantitative study performed as part of this thesis provides further evidence that high impact HRSA is associated with more favourable bone health in adolescence and early adulthood, and while participation in sport in New Zealand is common until late teens, subsequently HRSA often decreases during the window of PBM acquisition. Knowledge of factors impacting bone health is poor, and barriers and facilitators to HRSA have been identified. Further work to consider how best to address these knowledge and evidence gaps is now warranted, including focus on young school to early adulthood populations to reduce their future fragility fracture risk.</p>
The Relationship Between Non-elite Sporting Activity and Calcaneal Bone Density in Adolescents and Young Adults: A Narrative Systematic Review