Physical activity and cardiovascular fitness during childhood and adolescence: Association with retinal nerve fibre layer thickness in young adulthood

Precis: Higher physical working capacity (PWC) at age 17 was associated with thicker peripapillary retinal nerve fiber layer (pRNFL) at age 20, suggesting a mechanistic link between cardiovascular fitness and neuroretinal integrity.

Purpose: Physical activity and cardiovascular fitness have been linked with lower odds of developing glaucoma. We tested the hypothesis that early beneficial effects of physical activity and cardiovascular fitness can be observed by measuring the pRNFL thickness in young healthy adults.

Methods: The Raine Study is a longitudinal study that has followed a cohort since before their births in 1989-1992. Parent-reported physical activity was collected between 8 and 17 years, and latent class analysis was used to identify the participants' physical activity trajectories. At the 20-year follow-up (participants' mean age=20.1±0.4 y), participants' metabolic equivalent of task-minutes/week was determined using self-reported physical activity data. Participants' PWC was assessed at the 14- and 17-year follow-ups to estimate their level of cardiovascular fitness. An eye examination, which included spectral-domain optical coherence tomography imaging, was conducted at the 20-year follow-up for 1344 participants.

Results: Parent-reported or participant-reported physical activity was not associated with pRNFL thickness. However, higher PWC at 17 years was associated with thicker pRNFL globally [by 0.3 µm; 95% confidence interval (CI)=0.2-0.6; P<0.001], superotemporally (by 0.4 µm; 95% CI=0.1-0.7; P=0.013), inferonasally (by 0.7 µm; 95% CI=0.1-0.9; P=0.002), and nasally (by 0.4 µm; 95% CI=0.1-0.7; P=0.006) per 10 Watt increase in PWC.

Conclusions: The association between estimated cardiovascular fitness and pRNFL thickness suggests there may be overlapping mechanisms for cardiovascular health and retinal ganglion cell integrity. While the effect sizes were small, it is possible that larger effects and clinically significant associations may arise as we follow this cohort of participants through their later adulthood.