Cohort profile: The Health, Food, Purchases and Lifestyle (SMIL) cohort - a Danish open cohort.

PURPOSE:The Health, Food, Purchases and Lifestyle (SMIL) cohort is a prospective open Danish cohort that collects electronic consumer purchase data, which can be linked to Danish nationwide administrative health and social registries. This paper provides an overview of the cohort's baseline characteristics and marginal differences in the monetary percentage spent on food groups by sex, age and hour of the day. PARTICIPANTS:As of 31 December 2022, the cohort included 11 214 users of a smartphone-based receipt collection application who consented to share their unique identification number for linkage to registries in Denmark. In 2022, the composition of the cohort was as follows: 62% were men while 24% were aged 45-55. The cohort had a median of 63 (IQR 26-116) unique shopping trips. The cohort included participants with a range of health statuses. Notably, 21% of participants had a history of cardiovascular disease and 8% had diabetes before donating receipts. FINDINGS TO DATE:The feasibility of translating consumer purchase data to operationalisable food groups and merging with registers has been demonstrated. We further demonstrated differences in marginal distributions which revealed disparities in the amount of money spent on various food groups by sex and age, as well as systematic variations by the hour of the day. For example, men under 30 spent 8.2% of their total reported expenditure on sugary drinks, while women under 30 spent 6.5%, men over 30 spent 4.3% and women over 30 spent 3.9%. FUTURE PLANS:The SMIL cohort is characterised by its dynamic, continuously updated database, offering an opportunity to explore the relationship between diet and disease without the limitations of self-reported data. Currently encompassing data from 2018 to 2022, data collection is set to continue. We expect data collection to continue for many years and we are taking several initiatives to increase the cohort.