Is There a Causal Relationship between Physical Activity and Bone Microarchitecture? A Study of Adult Female Twin Pairs.

• Main Authors: Nissen, Frida Igland, Esser, Vivienne FC, Bui, Minh, Li, Shuai, Hopper, John L, Bjørnerem, Åshild, Hansen, Ann Kristin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2023
• Subjects: CORTICAL BONE; HIGH-RESOLUTION PERIPHERAL QUANTITATIVE COMPUTED TOMOGRAPHY; ICE FALCON; OSTEOPOROSIS; PHYSICAL ACTIVITY; Female; Humans; Absorptiometry; Photon; Bone and Bones; Bone Density; Cross-Sectional Studies; Exercise; Radius; Tibia; Adult; Middle Aged; Aged; Norway; Northern Norway
• Online Access: https://www.repository.cam.ac.uk/handle/1810/350328

Funder: The Northern Norway Regional Health Authority funded the study (HNF 1471‐19). Funder: JLH is supported by an NHMRC Fellowship (GMT1137349). Funder: SL is supported by a Victorian Cancer Agency Early Career Research Fellowship (ECRF19020). Funder: VFCE is supported by an Australian Government Research Training Program (RTP) Scholarship. The reasons for the association between physical activity (PA) and bone microarchitecture traits are unclear. We examined whether these associations were consistent with causation and/or with shared familial factors using a cross-sectional study of 47 dizygotic and 93 monozygotic female twin pairs aged 31-77 years. Images of the nondominant distal tibia were obtained using high-resolutionperipheral quantitative computed tomography. The bone microarchitecture was assessed using StrAx1.0 software. Based on a self-completed questionnaire, a PA index was calculated as a weighted sum of weekly hours of light (walking, light gardening), moderate (social tennis, golf, hiking), and vigorous activity (competitive active sports) = light + 2 * moderate + 3 * vigorous. We applied Inference about Causation through Examination of FAmiliaL CONfounding (ICE FALCON) to test whether cross-pair cross-trait associations changed after adjustment for within-individual associations. Within-individual distal tibia cortical cross-sectional area (CSA) and cortical thickness were positively associated with PA (regression coefficients [β] = 0.20 and 0.22), while the porosity of the inner transitional zone was negatively associated with PA (β = -0.17), all p < 0.05. Trabecular volumetric bone mineral density (vBMD) and trabecular thickness were positively associated with PA (β = 0.13 and 0.14), and medullary CSA was negatively associated with PA (β = -0.22), all p ≤ 0.01. Cross-pair cross-trait associations of cortical thickness, cortical CSA, and medullary CSA with PA attenuated after adjustment for the within-individual association (p = 0.048, p = 0.062, and p = 0.028 for changes). In ...