The relationship between habitual water intake and dry eye disease.

PURPOSE: The purpose of this study is to test the hypothesis that greater habitual water intake is associated with lower risk of dry eye disease (DED). METHODS: We included 51 551 participants from the population-based Lifelines cohort (mean age = 51.2 years) in this cross-sectional association study. DED was assessed using the Women's Health Study (WHS) dry eye questionnaire. Water intake was calculated from food frequency questionnaires. Logistic regressions were used to analyse the relationship between DED and water intake or 24-h urine volume, corrected for age, sex, body mass index, physical activity, smoking status, education, income, 48 comorbidities, and 15 medication groups. The main outcome measure was WHS-defined DED. Highly symptomatic dry eye and clinical diagnosis of DED were secondary outcomes. RESULTS: In total, 9.1% of the population had WHS-defined DED. Higher water intake was associated with increased prevalence of WHS-defined DED (OR: 1.011 per 100 ml/day, 95% CI: 1.004-1.017, p = 0.003). After excluding those with a clinical diagnosis, greater water intake was still tied to increased risk of having DED symptoms (OR: 1.010 per 100 ml/day, 95% CI: 1.006-1.015, p < 0.001). Higher 24-h urine volumes were also associated with higher risk of WHS-defined DED (OR: 1.010 per 100 ml/day, 95% CI: 1.005-1.015, p < 0.001). CONCLUSIONS: In this large, population-based study, higher water intake was not tied to reduced risk of DED. Rather, it was associated with a modest increased risk of DED. Interventional studies are needed to fully understand the effect of water intake on DED, but this study found no evidence that greater water intake is beneficial for DED.