Beyond biological resilience: sex differences in stress and health across 2,000 years in Milan, Italy

Comparative and contemporary literature has long established that females have a biological advantage in the prevalence, severity, and mortality of many conditions. Here, we test sex differences in stress burden in Milan over 2,000 years. We posit that females will show lower risks of physiological stress markers because of female biological advantages in morbidity, while males will be more affected by mechanical stress markers due to historically gendered divisions of labor in Milan. We considered 721 individuals (345 females and 376 males) from five historical periods: Roman (I-V c. AD, n = 143), Early Medieval (VI-X c. AD, n = 94), Late Medieval (XI-XV c. AD, n = 167), Modern (XVI-XIX c. AD, n = 117), and Contemporary (XX-XXI c. AD, n = 200). Thirteen stress markers were recorded and grouped into biologically relevant categories: physiological stress, growth disruption, infection-related pathology, and mechanical loading. Logistic regressions and multivariate generalized linear models were fitted controlling for historical period, as well as age for mechanical stress. Sex effect was significant on markers of physiological stress and mechanical loading, but it was dominated by the effects of period and age. Males showed significantly higher odds of porotic hyperostosis, cribra orbitalia, Schmorl’s nodes, and marked entheseal changes, whereas females had higher odds of post-cranial porous lesions and signs of upper respiratory tract infection. In addition to clear evidence of female biological advantage, the study shows how historical and environmental variation shaped disease burden and modified, obscured, or reversed expected biological advantages in historic Milan.