Exploring the effects of weaning age on adult infectious disease mortality among 18th–19th century Italians

Objectives: The developmental origins of health and disease (DOHaD) hypothesis describes how early childhood stress affects morbidity and mortality later in life. The role of early childhood stress in mortality from infectious disease is understudied. Stressors in early childhood that weaken the immune system may result in increased susceptibility to infectious disease in adulthood. Weaning is one of the earliest potential periods of significant stress in early childhood. This research investigates the effect of weaning after ~6 months of age on cholera mortality among 18th-19th-century Italian populations by determining if earlier breastfeeding cessation is associated with earlier mortality, analyzing childhood dietary variation and physiological stress markers, and determining if age-at-weaning completion differs between catastrophic and attritional populations. Methods: Serial dentin stable carbon and nitrogen isotope analyses from canines are compared between catastrophic (n = 45) and attritional groups (n = 23). Canines are sectioned serially from crown to apex, and the increment's δ15 N and δ13 C are used to estimate age-at-weaning completion. Results: Catastrophic and attritional groups exhibit similar age-at-weaning completion (~2.8 years). Seventy-four percent of individuals lack elevated δ15 N values in dentin that formed during infancy. Conclusions: Age-at-weaning completion was not a predisposing factor in cholera mortality in adulthood in this sample. Age-at-weaning completion may not be significantly associated with infectious disease mortality because weaning completion likely occurred after infants had adapted to consuming contaminated weanling foods. Individuals without detectable weaning curves may represent infants who received supplementary foods since birth or were weaned before the age of 6-9 months.