Aim/hypothesis <p>Chronotype reflects an individual’s circadian rhythm, which may be associated with lifestyle habits and metabolic profiles. A few studies have shown that disruptions in circadian rhythms may contribute to the pathogenesis of diabetic retinopathy. This prospective observational study aimed to investigate the association between lifestyle habits, including chronotype, and the incidence and progression of diabetic retinopathy.</p> Methods <p>The study participants were 731 Japanese outpatients with type 2 diabetes and no apparent history of cardiovascular disease. Lifestyle habits were assessed using questionnaires, including the Morningness–Eveningness Questionnaire (MEQ), to determine chronotype at baseline and at years 2 and/or 5. The composite endpoint of this study was the incidence and progression of diabetic retinopathy. The mean values of lifestyle factors were calculated by averaging the values from baseline to the date of endpoint onset or the end of the follow-up period. A Cox proportional hazards model was used to determine the association between lifestyle habits and the composite endpoint.</p> Results <p>During the median follow-up period of 7.56 years (IQR 6.04–7.95), the composite endpoint was observed in 57 participants. Multivariate Cox models showed a significant negative association between the mean MEQ scores and the composite endpoint (HR 0.95; 95% CI 0.91, 0.99). In a sensitivity analysis in which the participants were divided into three groups based on mean MEQ scores, the ‘more evening’ chronotype group had a 2.29-fold higher risk (95% CI 1.15, 4.55) of the composite endpoint compared with the ‘neither’ group. Compared with the ‘more morning’ chronotype group, the more evening chronotype group had a 2.09-fold higher risk of the composite endpoint (95% CI 1.05, 4.13). Participants with the more evening chronotype experienced worsening glucose management over time compared with those with other chronotypes. However, a significant negative association between the mean MEQ scores and the composite endpoint was still observed after adjusting for the mean HbA_1c levels over time.</p> Conclusions/interpretation <p>People with type 2 diabetes and an evening chronotype have worsened glucose management and are at a higher risk of incidence and/or progression of diabetic retinopathy.</p> Trial registration <p>University Hospital Medical Information Network Clinical Trials Registry UMIN000010932</p> Graphical Abstract <p></p>