Reductions in intra-ocular pressure after acute aerobic exercise: a meta-analysis

Methodological quality of the review: Low confidence

Author: Roddy G, Curnier D, Ellemberg D

Geographical coverage: United States of America (USA), United Kingdom (UK), Greece, Australia, China, Japan and Turkey

Sector: Glaucoma

Sub-sector: Intra-ocular pressure and acute aerobic exercise

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: High intra-ocular pressure (IOP) is the main risk factor for primary open angle glaucoma (POAG). Aerobic exercise is known to reduce IOP, therefore it is important to analyse studies that have investigated the effect of acute aerobic exercise on IOP.

Objectives: To analyse studies on the effects of acute aerobic exercise on IOP to verify the influence of participant characteristics, exercise intensity and duration.

Main findings: In this review, 35 empirical studies were identified. Ten studies including 14 independent groups were included. One study each was conducted in Turkey, Greece, UK, Australia, Wales and Japan. Two studies each were conducted in China and USA.

Findings from the pooled analysis suggested that the outcome variable of post-exercise change in IOP produced a significant effect of exercise, almost two-fold greater for sedentary populations than for normally active populations (ES = 24.198; CI, 25.151 to 23.245); ES = 22.340; CI, 23.305 to 1.375, respectively). The significant effect of exercise on IOP is potentially mediated by group allocation.

In addition, findings indicated that intensity and duration do not contribute to the overall effect size (ES), nor do they explain the difference between sedentary and normally active populations. Based on these findings, authors concluded that there is a clear effect of aerobic exercise on IOP, particularly for the inactive group when compared with the normally active group.

Authors note that there is a need for research on this topic in elderly and clinical populations. Future research needs to concentrate on whether that transient post-exercise reduction can be stabilised with the introduction of a regular aerobic exercise program.

Methodology: Electronic databases PUBMED, Web of Science and EMBASE were searched for relevant articles. Other databases and reference lists of identified articles were searched for other relevant articles and unpublished studies.

The following inclusion criteria were applied:

(a) Studies must include post-exercise IOP measured after the first acute bout of aerobic exercise on a given test day and associated SD or standard error (SE) or raw participant data.

(b) Participants should be sedentary, normally active or athletic (excluding professional athletes) displaying no pre-existing ocular pathologies or IOP more than 18 mm Hg.

(c) To reduce the likelihood of age-related pathologies that may affect the eye, all participants should not be older than 55 years of age,

(d) Exercise should be aerobic in nature and the intensity must be quantifiable using physiological target measures such as a percentage of V̇_O2max (a measure of maximal oxygen uptake) or a sub-maximal estimation of maximum heart rate (MHR).

(e) Exercise should be no less than two minutes, ensuring at least partial recruitment of the aerobic system and no more than 60 minutes within daylight hours to constrain the effect of diurnal variation. The primary outcome variable was post-exercise IOP. The effect of exercise intensity and duration was also evaluated.

An independent reviewer was consulted for all questions regarding inclusion of a potentially relevant study. Authors extracted data of included studies, including type and duration of exercise, patient characteristics etc.

A random-effects model was used to produce sub-group analyses and a forest plot. Meta-regressions were used to verify the impact of group allocation, intensity and duration on the inter-study variability of the ES.

Applicability/external validity: Authors did not discuss the applicability/external validity of findings.

Geographic focus: Authors included studies from low, middle and high-income countries, and as such findings may be generalized.

Summary of quality assessment: Overall, there is low confidence in the conclusions about the effects of this study as important limitations were identified. Authors conducted a thorough search of the literature, however it’s not clear if language bias was avoided. In addition, it’s not clear if two reviewers independently screened and abstracted data of included studies. Authors did not address the risk of bias of included studies.