Opium Use and the Risk of Cataract: a Hospital-based, Group-matched, Case–control Study in Iran

Purpose
Cataract is the most prevalent cause of reversible blindness worldwide. Although studies have identified risk factors for cataract, its association with opium use has not been studied. This study aimed to evaluate the association between opium use and cataract in Iran in 2020.

Methods
In a hospital-based, group-matched case–control study in Kerman, a city in southeast Iran, 160 new cases of cataract and 320 controls without cataract underwent ophthalmological examination and were interviewed. Logistic regression models tested the association between cataract and history of opium use, adjusting for demographic characteristics and history of hypertension, coronary heart disease, renal disease, smoking, alcohol use, and unprotected sun exposure.

Results
After controlling for potential confounders, opium use increased the odds of cataract, exhibiting a dose–response relationship. The adjusted odds ratio (aOR) for mild use was 1.44 (95% confidence intervals [CI] 0.80–2.58), and 2.10 (95% CI 1.04–4.25) for heavy use. Exposure to opium juice use further increased the odds of cataract (aOR 2.24, 95% CI 1.00–5.10). Other significant associations with cataract were lower education level (aOR 5.46, 95% CI 2.45–11.29), being unmarried (aOR 2.88, 95% CI 1.65–5.00), both underweight (BMI <18.5, aOR 5.27, 95% CI 2.02–13.70) and overweight (BMI >25, aOR 1.82, 95% CI 1.15–2.87), and family history of cataract (aOR 2.07, 95% CI 1.32–3.23).

Conclusion
Our study provides evidence that opium use could increase the odds of cataract. Results also support the association of cataract with other modifiable risk factors, such as very low and high BMI and unprotected sun exposure.