Purpose Cancer-related genes and pathways have recently been implicated in a genome-wide meta-analysis of head size. In the current study, we aimed to evaluate the association between adult head circumference and the risk of cancer. Methods This is a cohort study using data from the Hong Kong Osteoporosis Study, where 1,301 participants aged 27–96 years with head circumference measured between 2015 and 2019, and without a hist...