Why do some women break their bones while others do not?

PhD student:
Frida Igland Nissen, University Hospital of North Norway, UiT – The Arctic University of Norway

Supervisors:
Associated professor Ann Kristin Hansen (main supervisor), University Hospital of North Norway, UiT – The Arctic University of Norway
Professor Åshild Bjørnerem, Oslo University Hospital, UiT – The Arctic University of Norway

Collaborator:
Vivienne FC Esser, University of Melbourne, Melbourne, Australia

The overall aim of this thesis was to explore the pathophysiology and increase our understanding of why some women develop bone structure decay, resulting in bone fragility and fractures. We wanted to explore the relationships between bone microarchitecture and height, weight, and physical activity (PA). By using a regression model for twin data, Inference on Causation from Examination of Familial Confounding (ICE FALCON), we could examine whether the potential associations between bone architecture and height, weight and PA were consistent with causation, despite of having a cross-sectional study design. Furthermore, we wanted to investigate whether assessment of the bone architecture measured at the proximal femur could improve the prediction of fractures beyond areal bone mineral density (aBMD) by using DXA or fracture risk assessment by using the FRAX-tool. 

The specific aims were to: 

I – Examine the associations of height and weight with bone microarchitecture at the distal tibia, and whether there are differences in how height and weight influence the cortical and trabecular bone traits. We also wanted to examine whether the relationships of height and weight with bone microarchitecture are consistent with causation, shared familial factors, or a mixture of both.

II – Investigate the association of PA with bone microarchitecture at the distal tibia and examine whether the relationship of PA with bone microarchitecture is consistent with causation, shared familial factors, or a mixture of both causation and shared familial factors. 

III – Examine whether cortical porosity of the proximal femur predicts any incident fracture, hip fractures, or major osteoporotic fractures, independent of femoral neck (FN) aBMD and FRAX score in postmenopausal women.