Retinal vascular fractal dimension measurements in patients with obstructive sleep apnea syndrome: a retrospective case-control study.

STUDY OBJECTIVES
We performed a case-control study to investigate the correlation between the AHI and the retinal vascular fractal dimension (FD).


METHODS
We selected 527 individuals who underwent polysomnography during health checkups at the Huadong Sanatorium from January to December 2021 as the study population, of whom 468 were included and 59 were excluded. All participants underwent a detailed health examination, including medical history assessment, physical examination, assessment of lifestyle factors, fundus photography, and laboratory examinations. The retinal vasculature was quantitatively assessed using Singapore I vessel assessment (SIVA) software. The relationship between the AHI and the retinal vessel quantitative was examined by multiple linear regression analyses and restricted cubic spline (RCS).


RESULTS
Among the 468 studied individuals, the average age was 51.51 (43-58), with 369 (79.01%) males and 99 (20.99%) females. According to the AHI indicator, 355 individuals were diagnosed with OSAS, with an average AHI of 17.00 (9.200- 30.130); 113 individuals were classified as controls, with an average AHI of 2.13(0.88-3.63). In multiple linear regression, following varying degrees of adjustment for confounding factors, FD was reduced by 0.013 (P =.012, 95% CI: -0.024 to -0.003), FDa was reduced by 0.013 (P =.019, 95% CI: -0.024 to -0.002), and FDv was reduced by 0.014 (P =.08, 95% CI: -0.024 to -0.004) in the high AHI group compared with the low AHI group. All tests for trend P less than 0.05. The RCS in the overall OSA population and the individuals without diabetes revealed a U-shaped pattern of decreasing, then increasing, FD, FDa, and FDv with a rising AHI. In the OSA individual with diabetes, FD, FDa, and FDv gradually decreased with increasing AHI.


CONCLUSIONS
The FD is associated with the AHI in OSA individuals. The link between the AHI and FD varied for OSA individuals with and without diabetes.