Time Trends in Bone Mass and Fracture Incidence in Children Bergman, Erika 2021 Document Version: Publisher's PDF, also known as Version of record Link to publication Citation for published version (APA): Bergman, E. (2021). Time Trends in Bone Mass and Fracture Incidence in Children. Lund University, Faculty of Medicine. 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LUND UNIVERSITY PO Box 117 221 00 Lund +46 46-222 00 00 ERIKA BERGMAN AN ECOLABEL 3041 0903 NORDIC SW Time Trends in Mass Bone and Trends Time Fracture Incidence in Children ryck, Lund 2021 Time Trends in Bone Mass and Fracture Incidence in Children Printed by Media-T ERIKA BERGMAN DEPARTMENT OF CLINICAL SCIENCES AND ORTHOPEDICS | LUND UNIVERSITY Clinical and Molecular Osteoporosis Research Unit, Department of Clinical Sciences and Orthopedics, Skåne University Hospital, Malmö 210485 Lund University, Faculty of Medicine 2021:42 Doctoral Dissertation Series 2021:42 ISBN 978-91-8021-048-5 789180 ISSN 1652-8220 9 Time Trends in Bone Mass and Fracture Incidence in Children Erika Bergman DOCTORAL DISSERTATION by due permission of the Faculty of Medicine, Lund University, Sweden. To be defended at Video conference room 28 11 026, Clinical Research Centre (CRC). The audience is invited to Lecture Hall “Medelhavet”, Wallenberg lab, Inga Marie Nilssons gata 53 Or via Zoom: https://lu-se.zoom.us/j/69044702287 May 20, 2021 at 09.00. Faculty opponent Associate Professor Michael Möller Ortopediska kliniken, Sahlgrenska Universitetssjukhuset, Göteborg 1 Organization Document name LUND UNIVERSITY DOCTORAL DISSERTATION Clinical and Molecular Osteoporosis Date of issue 2021-05-20 Research Unit, Department of Clinical Sciences and Orthopedics, Skåne University Hospital, Malmö Author: Erika Bergman Sponsoring organization Title and subtitle Time Trends in Bone Mass and Fracture Incidence in Children Abstract Background: It is currently estimated that one third of all children will sustain fractures. However, there may also be time trends in pediatric fracture incidence. When predicting future fracture incidence, it is further important to evaluate bone mass, as low bone mass is a strong predictor of fractures. Such evaluation would help the society to allocate health care resources adequately. Aims: The aims of this thesis were to in children (i) update fracture epidemiology/etiology, (ii) identify possible time trends in fracture incidence, and (iii) identify possible differences in bone mass over time. Methods: In the epidemiological studies we included all types of fractures (Paper I), and the two most common type of fractures, distal forearm fractures (Paper II), and hand fractures (Paper III), that Malmö children aged 0–15 years had sustained in 2014–2016. Fractures were identified through the Skåne University Hospital (SUS) diagnosis registry, the radiological archive and medical charts. We compared these data with published data from 14 evaluated years during the period 1950–2006. Time trends were evaluated using joinpoint regression analysis and differences between two specific periods with incident rate ratios (IRRs) with 95% confidence intervals (95% CIs). We also measured distal forearm bone mineral density (BMD; g/cm2) by single photon absorptiometry (SPA) in 442 children aged 7–15 during the years 2017–2018 and compared these data with BMD in 116 children aged 7– 15 measured in 1979–1981 (Paper IV). We present BMD versus age in the two cohorts as scatter plots with fitted linear regression slopes with 95% CI. Predicted BMD at age 16 was estimated with help of the slopes, with the difference between the two cohorts presented as proportional difference (%) and difference in standard deviation (SD). Results: The pediatric fracture incidence in 2014–2016 was 1,786/105 person-years, for distal forearm fractures 546/105 person-years, and for hand fractures 339/105 person-years. The pediatric age-adjusted fracture incidence increased from 1950 to 1979 and was thereafter stable, the age-adjusted distal forearm fracture incidence increased from 1950 to 2016, while the age-adjusted hand fracture incidence increased from 1950 to 1979 and decreased after that. The only difference in age-adjusted incidences, when comparing the period 2014–2016 with the most recent evaluated period 2005–2006, was a higher incidence in girls for all types of fractures in 2014– 2016. Sports and playing injuries were common fracture-related activities. Children measured in 2017–2018 had an inferior BMD versus age slope than children measured in 1979–1981 (– 5.6 mg/cm2/year, 95% CI: –9.6 to –1.5). The predicted BMD in 16-year-old boys in 2017–2018 was about 10% (– 0.9 SD) lower than the predicted BMD value in 16-year-old boys 1979–1981. The corresponding value for 16-year- old girls in 2017–2018 was about 11% lower (–1.1 SD) than the predicted BMD value in 16-year-old girls 1979– 1981. Conclusions: Pediatric age-adjusted fracture incidences have been stable in recent decades, while some fractures, such as distal forearm fractures, have increased, and others, such as hand fractures, have decreased. Children seem nowadays to develop lower BMD than four decades ago, changes that may indicate the risk of a future increase in the prevalence of osteoporosis and incidence of fractures. Key words: fractures, epidemiology, etiology, distal forearm, hand, bone mineral density, BMD, time trends, children, boys, girls Classification system and/or index terms (if any) Supplementary bibliographical information Language English ISSN and key title 1652-8220 ISBN 978-91-8021-048-5 Recipient’s notes Number of pages 94 Price Security classification I, the undersigned, being the copyright owner of the abstract of the above-mentioned dissertation, hereby grant to all reference sources permission to publish and disseminate the abstract of the above-mentioned dissertation. Signature Date 2021-04-11 2 ‘ Time Trends in Bone Mass and Fracture Incidence in Children Erika Bergman 3 Cover photo “Broken branch” in Bölarp, Laholm, Sweden, by Erika Bergman Copyright pp 1–94 (Erika Bergman) Paper 1 © Taylor and Francis (open access) Paper 2 © Thieme (used with permission) Paper 3 © BMC (open access) Paper 4 © by the Authors (Manuscript unpublished) Clinical and Molecular Osteoporosis Research Unit Department of Clinical Sciences and Orthopedics Skåne University Hospital, Malmö Faculty of Medicine, Lund University, Sweden ISBN 978-91-8021-048-5 ISSN 1652-8220 Printed in Sweden by Media-Tryck, Lund University Lund 2021 4 To my friends and family “All we have to decide is what to do with the time that is given us.” ȸ J.R.R. Tolkien, The Fellowship of the Ring 5 Table of Contents Abstract ................................................................................................................... 8 List of papers......................................................................................................... 10 Abbreviations ........................................................................................................ 11 Introduction .......................................................................................................... 13 Bone ............................................................................................................. 13 Bone tissue .......................................................................................... 13 Growth, modeling, and remodeling in bones ...................................... 14 Bone mass and peak bone mass ........................................................... 15 Fractures and measurements ........................................................................ 16 Bone strength ....................................................................................... 16 Bone measurement .............................................................................. 17 Single photon absorptiometry .............................................................. 18 Fractures in children ............................................................................ 19 Fracture epidemiology.................................................................................. 20 Pediatric fractures ................................................................................ 20 Factors affecting fracture incidence .................................................... 21 Fracture etiology .......................................................................................... 23 Classification systems ......................................................................... 23 Injury prevention in Sweden ..............................................................