Inequality embodied: A systematic review of the spatial and temporal variation of cortical bone health measures and socioeconomic status

Background: Like many other chronic conditions, osteoporosis has been proposed to follow a social gradient where socio-economic disadvantage is associated with a higher diagnosis and fracture risk. While evidence for this association has come from biomedical research, and independent observations from studies on ancient human remains, the relationship between measured socioeconomic status (SES) and various parameters of 'bone health' appears inconsistent across different populations, methods, and timeframes. In this review article, we apply a comprehensive social and evolutionary framework to assess the spatial and temporal variation of SES on bone health. Methods: A systematic review of the current biomedical and archaeological literature examined the association between SES and bone health. Peer reviewed articles were obtained through Google Scholar and PubMed. Four quantitative indicators of bone health were considered: bone mineral density (BMD), cortical index, osteoporotic fractures, and histomorphometry. Results: Forty articles were identified, of which 30 reported a significant association between low SES and low BMD and/or high fracture risk. The earliest evidence for socially patterned osteoporosis was possibly in Ancient Egypt (2687-2191 BCE). Conclusion: The examined literature generally supported the association between social disadvantage and poor bone health outcomes, following the social gradient. However, we found that research on both modern and archaeological skeletal samples does not always account for intraskeletal variability or use comparable methods when assigning SES, creating between-study inconsistencies. We highlight the contributions of archaeological studies on social conditions and bone fragility, emphasising that socially patterned osteoporosis is not a solely modern-day occurrence.