Sleep duration and the risk of major eye disorders: a systematic review and meta-analysis

Authors: Zhou M, Li DL, Kai JY, Zhang XF, Pan CW

Geographical coverage: China, Korea, USA, Singapore, Spain, South Africa, India and Indonesia

Sector: Eye disorders and sleep duration

Sub-sector: Risk

Equity focus: Not reported

Study population: Patients with eye disorders

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Visual impairment and blindness are pressing global public health concerns, with major eye disorders such as myopia, glaucoma, cataract, age-related macular degeneration (AMD), and diabetic retinopathy (DR). Understanding modifiable risk factors is vital for effective prevention. Inappropriate sleep duration has already been linked to various health issues such as diabetes and all-cause mortality. Emerging evidence suggests potential associations between sleep duration and eye disorders, yet the findings remain inconsistent and often contradictory. Some studies report positive or inverse relationships, while others show no significant link. Despite this, no comprehensive review or meta-analysis has yet synthesised this growing body of research.

Objectives:

To systematically review the published literature on the association between sleep duration and major eye disorders including myopia, glaucoma, cataract, AMD, and DR.

Main findings:

In total, 21 observational studies (777,348 participants) published between 2002 and 2020 were included in this meta-analysis. Of these, 17 were cross-sectional, 3 were longitudinal, and 1 was a case-control study. The majority of the included studies (n = 8) were conducted in China, with 4 studies in Korea, 3 in the USA, 2 in Singapore, and 1 each in Spain, South Africa, India and Indonesia. The overall quality of the eligible studies ranged from moderate to high.

Findings showed that compared with normal sleep duration, long sleep duration was significantly linked to the risk of DR (odds ratio, OR: 1.84, 95% Confidence Interval [CI]: 1.24 to 2.73), but not associated with the risk of myopia (OR: 0.84, 95% CI: 0.58 to 1.21), glaucoma (OR: 1.80, 95% CI 0.66 to 4.95), AMD (OR: 1.29, 95% CI: 0.71 to 2.33), or cataract (OR: 0.91, 95% CI: 0.77 to 1.08). On the other hand, in comparison with normal sleep, short sleep was significantly related to the risk of cataract (OR: 1.20, 95% CI: 1.05 to 1.36), but not associated with the risk of myopia (OR: 1.06, 95% CI 0.88 to 1.26), DR (OR: 1.00, 95% CI: 0.78 to 1.28), glaucoma (OR: 1.11, 95% CI: 0.84 to 1.46), or AMD (OR: 1.49, 95% CI: 0.40 to 5.59). Subgroup analyses revealed that long sleep (more than 9 hours) was significantly associated with an increased risk of DR (OR: 2.09, 95% CI: 1.27 to 3.45), but a decreased risk of myopia (OR: 0.51, 95% CI: 0.31 to 0.83).

Methodology:

The searches were conducted in PubMed, Embase, Web of Science, and Cochrane Library to identify primary studies that demonstrated the relationship between sleep duration and major eye disorders. The studies published in English up to July 2021 were included in this review. Reference lists of the included studies were also scanned to identify additional relevant publications.

Two reviewers independently screened the articles. Discrepancies between the reviewers were resolved through discussion or by contacting a third reviewer. Relevant data was extracted in a standardised data collection form. The methodological quality of the eligible cross-sectional studies was evaluated by the Agency for Healthcare Research and Quality, and of case-control and cohort studies was assessed using the Newcastle-Ottawa Scale. The findings were synthesised using meta-analysis, and multiple subgroup analyses were performed. Heterogeneity was assessed using I² statistics, and publication bias was assessed using a funnel plot and Egger’s test.

Applicability/external validity:

The review noted that most of the included studies were cross-sectional in design, limiting the ability to draw causal inferences. Additionally, the predominance of studies conducted in Asia may constrain the generalisability of the findings to other populations. The authors emphasised the need for future research to clarify causal relationships and explore the underlying biological mechanisms linking sleep behaviours to major eye disorders.

Geographic focus:

The review did not apply any geographical limits. The included studies were conducted in China, Korea, USA, Singapore, Spain, South Africa, India and Indonesia.

Summary of quality assessment:

Overall, there is low confidence in the review conclusions. The literature searches were limited to identifying articles published in the English language only and the review did not specify how many reviewers independently performed data extraction.