The association between clinically diagnosed insomnia and age-related macular degeneration: a population-based cohort study

Purpose: The decreased level of melatonin, the substance involved in the control of the sleep–wake cycle, has been reported among the patients with age-related macular degeneration (AMD). However, knowledge about the relationship between sleep disturbance and AMD is still limited. This longitudinal case–control study aims to investigate the risk of incident AMD among the patients with clinically diagnosed insomnia using the Taiwan National Health Insurance Research Database. Methods: The insomnia cohort (n = 15 465) consisted of newly diagnosed insomnia cases aged ≥55 years between 2000 and 2009. Subjects without insomnia, matched for age, gender and enrolment time, were randomly sampled as the control cohort (n = 92 790). Cox proportional hazard regressions were performed to calculate the hazard ratios (HR) of incident AMD for the two cohorts after adjusting for potential confounders. Results: Of the 108 255 sampled subjects, 2094 (1.9%) were diagnosed with AMD, including 214 (0.2%) with neovascular AMD, during a mean follow-up period of 5.1 ± 2.8 years. Insomnia patients were more likely to have subsequent AMD than those without insomnia (2.5% versus 1.8%, p < 0.001). Further, the incidence of exudative AMD was also higher in the insomnia cohort than the control cohort (0.3% versus 0.2%, p = 0.002). The adjusted HR was 1.33 (95% confidence interval [CI], 1.18–1.48, p < 0.001) for AMD and 1.67 (95% CI, 1.20–2.33, p = 0.002) for exudative AMD. Conclusions: Clinically diagnosed insomnia is an independent indicator for the increased risk of subsequent AMD development.