Abstract
BACKGROUND: This study investigates the non-linear relationship between blood pressure (BP) and diabetic retinopathy (DR), and the impact of BP variability on DR development. METHODS: This is a retrospective longitudinal cohort study. Nine hundred sixty-nine patients with type 2 diabetes and no DR at baseline between 1 January, 2018, and 31 May, 2023 were recruited from a single hospital. Participants underwent BP measurements at 3- to 6-month intervals. DR was assessed by indirect ophthalmoscopy or fundus photography at least every year. BP parameters including mean systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and pulse pressure (PP), along with their standard deviations (SDs), were calculated across visits. Logistic regression was used to analyse the associations between BP parameters and DR incidence. RESULTS: During a mean follow-up of 4.96 ± 0.96 years, 125 participants (12.9%) developed DR. A U-curve or J-curve association was found between mean SBP, DBP, MAP, and PP and DR risk, with the lowest risk observed at SBP 130-135 mmHg, DBP 75-80 mmHg, MAP 95-100 mmHg, and PP 50-55 mmHg. Greater visit-to-visit BP variability was independently associated with a higher risk of DR development. Each 1-mmHg increase in SD of SBP, DBP, MAP, and PP corresponded to odds ratios of 1.108 (CI: 1.06-1.16, p < 0.001), 1.111 (CI: 1.04-1.18, p < 0.001), 1.085 (CI: 1.04-1.13, p < 0.001), and 1.133 (CI: 1.08-1.19, p < 0.001), respectively. CONCLUSION: Extreme BP levels and greater visit-to-visit BP variability were associated with increased risk of DR. Maintaining stable and optimal BP may help prevent its development.