Risk factors for keratoconus: a Meta-analysis

Objective

To analyze the risk factors for keratoconus through a systematic review of secondary literature.

Methods

Analytical studies from Cochrane Library, PubMed, Embase database, CNKI, Wanfang Periodicals Database, VIP Chinese Science and Technology Journal Database published from January 2000 to May 2021 were searched, most of which were about the keratoconus occurrence and progression and the valid data were extracted.The case-control and the cohort studies were evaluated according to the Newcastle-Ottawa Scale.The categorical variables for combined effect size were odds ratio(OR) and 95% confidence interval (CI). The heterogeneity was evaluated via the Q test and I² test.The fixed-effect model was adopted when P>0.1 or I²≤50%, while the random effect model was adopted when I²>50%.The sources of heterogeneity in included evaluation indexes were analyzed through subgroup and sensitivity analysis.The publication bias was evaluated by Egger tests, Harbord tests, Peters tests and funnel plots.

Results

A total of 21 papers with 30 124 keratoconus cases and 59 012 control cases enrolled, including 18 case-control studies and 3 cohort studies, whose data were from 10 countries, were included.The NOS scores of the studies were not less than 7 points.The Meta-analysis results indicated that family history (OR: 8.68, 95% CI: 6.30-11.97), eye rubbing (OR: 4.62, 95% CI: 3.75-5.70), allergy (OR: 2.34, 95% CI: 1.73-3.16), obstructive sleep apnea (OR: 1.53, 95% CI: 1.12-2.10) and Down syndrome (OR: 7.09, 95% CI: 4.19-11.99) were the risk factors for keratoconus, and mitral valve prolapse (P>0.05) was not a risk factor for keratoconus, and diabetes (OR: 0.63, 95% CI: 0.50-0.79) was a protective factor for keratoconus.The subgroup analysis results indicated that the heterogeneity in allergy was partially due to the specific disease classification, and the heterogeneity in diabetes and obstructive sleep apnea was totally owing to the source of the cases.The sensitivity study showed that the results were robust after changing the analysis model.There was no bias in the included studies.

Conclusions

Family history, eye rubbing, allergy, obstructive sleep apnea and Down syndrome are risk factors for keratoconus, and diabetes is a protective factor for keratoconus.