Association Between Baseline Smoking Exposure and Incident Branch Retinal Vein Occlusion: A Retrospective Cohort Study

Purpose Beyond conventional vascular risk factors, we investigated whether baseline smoking exposure – a modifiable behavioral risk factor – is longitudinally associated with incident branch retinal vein occlusion (BRVO).Methods We analyzed 40,513 individuals (aged ≥40 years) undergoing serial health screenings (2011–2022). Incident BRVO was defined as new retinal hemorrhages in previously normal fundi, confirmed by masked specialists. Hypertension, diabetes, dyslipidemia, and decreased kidney function were defined by conventional criteria. Overweight/obesity was defined as BMI ≥ 23 kg/m2 or waist circumference ≥ 90 cm (men)/≥85 cm (women), and fatty liver by radiologist-confirmed ultrasonography. Smoking was classified as ever versus never. Variables with a log-rank p < 0.20 were entered into a multivariable Cox proportional hazards model.Results During a median follow-up of 5.2 years, 58 participants developed BRVO (0.14% of the cohort; 10-year Kaplan–Meier cumulative incidence, 0.30%). In multivariable analysis, age (HR, 1.05; 95% CI, 1.01–1.09), hypertension (HR, 2.27; 95% CI, 1.30–3.96), overweight/obesity (HR, 2.83; 95% CI, 1.39–5.75), and ever smoking (HR, 2.63; 95% CI, 1.20–5.79) were independently associated with incident BRVO.Conclusion In this longitudinal health-screening cohort, baseline ever smoking was independently associated with incident BRVO after adjustment for conventional vascular risk factors. These findings suggest that smoking, a modifiable exposure, may contribute to BRVO risk beyond established determinants, although the small number of events warrants cautious interpretation and confirmation in larger, multicenter studies.