We thank the Lothian Birth Cohort 1921 participants. We thank the Scottish Council for Research in Education for allowing access to the Scottish Mental Survey 1932. The Biotechnology and Biological Sciences Research Council (BBSRC) funded the phenotypic data collection and DNA preparation (project grant 15/SAG09977) and GWAS (project grant BB/F019394/1). The work was undertaken by The University of Edinburgh Centre for Cognitive Ageing and Cognitive Epidemiology, part of the cross council Lifelong Health and Wellbeing

Initiative (Centre grant G0700704/84698). Funding from the BBSRC, Engineering and Physical Sciences Research Council (EPSRC), Economic and Social Research Council EPZ5676 datasheet (ESRC) and Medical Research Council (MRC) is gratefully acknowledged. The MRC NSHD is funded by the UK Medical Research Council. DG is an NIHR Senior Investigator. Y-27632 cost RC receives support from the HALCyon programme funded by the New Dynamics of Ageing (RES-353-25-0001). DK and RH are supported by the UK Medical Research Council. MK is supported by NLBI, NIH (HL36310). TA is an ESRC PhD student. HALCyon is funded by the New Dynamics of Ageing cross council research programme. The HALCyon

study team also includes Jane Elliott, Catharine Gale, James Goodwin, Alison Lennox, Marcus Richards, Thomas von Zglinicki, John Gallacher, Gita Mishra, Chris Power, Paul Shiels, Humphrey Southall, Andrew Steptoe, Panos Demakakos, Kate Tilling, Lawrence Whalley, Geraldine McNeill, see more Leone Craig, Carmen Martin-Ruiz, Paula Aucott, Emily Murray, Zeinab Mulla, Mike

Gardner and Sam Parsons. Disclosure statement The authors declare no competing interests. “
“High bone mass (HBM) is a sporadic finding of generalised raised bone mineral density (BMD) on dual-energy X-ray absorptiometry (DXA) scanning, and when defined as such has a prevalence of 0.2% amongst a UK DXA-scanned population [1]. In a family of HBM cases due to activating low-density lipoprotein receptor-related protein 5 (LRP5) gene mutations, which enhance osteoblast activity, radiographs have shown widened long bones and cortices [2]. More recently high resolution peripheral quantitative computed tomography (HRpQCT) scanning of 19 individuals, from 4 families, with HBM caused by a T253I LRP5 mutation has identified increased cortical and trabecular BMD at the distal tibia [3]. However, much HBM is not explained by established LRP5 mutations, and detailed characterisation of bone structure in a large population of individuals with this unexplained HBM has yet to be described. Within such a HBM population it is not known whether HBM is associated with features of enhanced bone modelling (e.g. increased periosteal expansion) or reduced bone remodelling (e.g.