A recent study published in the Journal of Glaucoma evaluated the impact of physical activity (PA) on visual field (VF) progression rates in patients with primary open-angle glaucoma (POAG).
Give me some background.
The role of PA in glaucoma management has recently gained increasing attention, with previous studies indicating that PA can improve ocular perfusion pressure (OPP) and increase the level of brain-derived neurotrophic factor (BDNF).
However: There have been few longitudinal studies on this subject—and a recent investigation that used accelerometers demonstrated an association between increased walking and engagement in moderate-to-vigorous activities with slower VF loss in glaucoma patients.
Now talk about the study.
In this longitudinal study, POAG patients from the Diagnostic Innovations in Glaucoma Study (DIGS) and the African Descent and Glaucoma Evaluation Study (ADAGES) were included who had:
- ≥ 5 visits
- ≥ 2 years of follow-up VFs
- PA questionnaires (General Practice Physical Activity Questionnaire [GPPAQ]) at the baseline
And what was evaluated?
PA levels were assessed using the PA index (PAI), metabolic equivalents of task (MET)-minutes, and walking pace.
Take note: One MET is defined as the amount of oxygen consumed while sitting at rest and MET-minutes is calculated by multiplying the MET value of an activity by the number of minutes spent performing the activity.
- This is a simple and practical value for expressing the energy cost of PAs as a multiple of the resting metabolic rate.
Anything else?
Univariable and multivariable linear mixed-effects models were used to determine the impact of PA levels on the rates of VF mean deviation (MD) loss, with the multivariable analysis including:
- Age
- Sex
- Race
- Body mass index (BMI)
- Hypertension
- Diabetes
- Intraocular pressure (IOP)
- Baseline VF MD
Findings?
In total, 131 eyes from 80 POAG patients (43.8% female, 30.0% Black) were included in the analysis with a median follow-up of 4.9 years (interquartile range [IQR]: 4.0-6.7 years).
- The median age of patients was 68.6 years (IQR: 59.3-77.8 years) and the median baseline VF MD was -3.5 (IQR: -8.3 to -1.3).
In the univariable analysis: Slower VF MD loss was associated with:
- Active PAI category (0.30, 95% confidence interval [CI]: 0.01-0.58 dB/year vs. inactive PAI category, P = 0.041)
- Higher MET-minutes (0.14, 95% CI: 0.01-0.27 dB/year per 1,000 MET-minutes, P = 0.036).
Note: There were no significant associations with the moderately active or moderately inactive categories.
Anything else?
The research team did not find a significant association in the rate of VF MD loss with baseline VF MD (P = 0.263) or walking pace (P > 0.05).
In the multivariable analysis: After including glaucoma severity and other covariates, slower VF MD loss was associated with higher PA amounts (0.15, 95% CI: 0.02-0.28) dB/year per 1,000 MET-minutes, P = 0.024).
Expert opinion?
The study authors highlighted several pathways through which PA may impact the risk of glaucoma progression, including:
- PA may have a neuroprotective effect on retinal ganglion cells (RGCs)
- PA may help induce and sustain BDNF levels
- Some studies have shown an increase in BDNF with exercise while others have highlighted the importance of baseline levels
- Aerobic exercise has been found to decrease IOP by affecting the movement of aqueous humor through changes in catecholamine levels, plasma osmolality, and enlargement of Schlemm’s canal
- PA levels may mitigate the risk of glaucoma by indirectly preventing the development of metabolic disorders—such as diabetes, which are often linked to increased IOP
Limitations?
These included:
- PA was assessed using a questionnaire only at the onset of the study and PA values during follow-up were not recorded
- As the study participants were receiving long-term follow-up and mostly well-controlled, the impact of PA on IOP in this study was not as significant as anticipated
- The presence of diabetes was a strong and significant covariate in the study, which may have confounded the results—particularly in the PA activity category
- The interaction between glaucoma severity and PA levels may be important, so they ran additional analyses—though the results were not significant, suggesting that the impact of PA is unlikely to be mediated through IOP
Take home.
These findings suggest that higher amounts of self-reported PA amounts were associated with slower rates of VF MD loss in POAG patients.
However: Further research is required to determine whether increased PA is protective against glaucoma progression.