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Objective Disruption of circadian rhythms due to shift work is associated with an increased risk of diabetes and obesity. Adipose tissue plays a central role in metabolic processes related to lipid metabolism, endocrine signaling and energy regulation. The objective of this study is to evaluate epigenetic changes in adipose tissue in relation to night-shift work.Material and Methods Day and night-shift workers from the Swedish health sector were recruited to the EPHOR Night Shift study. Participants filled in a questionnaire about lifestyle, medical history, sleep, diet, physical activity, psychosocial factors, and work conditions. Adipose tissue biopsies were collected from a subgroup of 13 day- and 17 night-shift workers. Adipose tissue DNA was analyzed using the Illumina Infinium MethylationEPIC v2.0 BeadChip array. Statistical analysis will include epigenome-wide association study, as well as bioinformatic analysis of circadian rhythms and key adipose pathways. Additionally, we will estimate the biological age in adipose tissue using different epigenetic clocks.Results Participants were all women except from one, and their mean ± SD BMI (kg/m2) was 26.6 ± 5.6 for day-shift, and 26.2 ± 4.1 for night-shift workers. None of the participants reported having diabetes. Our epigenetic analysis will be focused on epigenome-wide changes in relation to night shift work, differential DNA methylation in candidate pathways, such as circadian rhythm genes (CLOCK, BMAL1, CRY1, PER1, PER2 and ZFHX3), in pathways related to lipid metabolism (e.g. SREBF1), and adipogenesis (PPARG). We will compare epigenetic age acceleration between shift work groups to assess the impact of shift work on biological ageing.Conclusion To our knowledge, this is the first human study on epigenetic changes in adipose tissue in relation to night shift work. The findings will provide mechanistic evidence of whether night shift work can result in reprogramming of metabolic processes in target tissue of circadian disruption.