Purpose
Higher UV exposure and residence at latitudes far from the equator has been linked to higher prevalence of exfoliation glaucoma (EG) or exfoliation glaucoma suspect (EGS). To date, the etiologic timing of UV exposure and its inter-relationship with residence has not been evaluated.
Methods
We conducted a cohort study in the United States using data from Nurses’ Health Study (NHS) and the Health Professionals Follow-up Study (HPFS) from 1980 (NHS) / 1986 (HPFS) to 2010. Biennial questionnaires were mailed to participants for follow-up. Participants were eligible to contribute person-time if they were 60+ years of age, free of glaucoma, had no history of cataract surgery history, reported eye exams and completed questions about the average hours/week spent outdoors in direct sunlight at the middle of the day for work or recreation purposes in the summer months at 3 life periods: high school to age 24 years, age 25-35 years, and age 36-59 years (questions were asked in 2006 in NHS and 2008 in HPFS); a total of 48,721 NHS women and 17,324 HPFS men contributed person-time. Incident EG/EGS cases (232 women and 32 men) were identified with biennial questionnaires and subsequently confirmed with medical records. Cohort-specific multivariable-adjusted rate ratios (MVRRs) and 95% confidence intervals (CIs) from Cox proportional hazards models for EG/EGS were estimated and then pooled with meta-analysis.
Results
Although no association was observed with greater time spent outdoors in summer months in the ages of 25-35 years or 36-59 years (p for linear trend or p-trends >0.15), we observed greater risks of EG/EGS with greater time spent outdoors in high school to age 24 years: the pooled MVRR for ≥11 hours per week compared with ≤1 hour per week spent outdoors was 2.04 (95% CI = 1.10, 3.77; p-trend=0.001). In the NHS, we observed that the association with greater time spent outdoors from high school to age 24 years was stronger in those residing in the same period in the southern tier (where the relative risk of EG/EGS is lower than in the northern tier; p for interaction = 0.05).
Conclusions
In this US study, greater time spent outdoors during the summer in young adulthood, particularly among those residing in the southern geographical tier, was associated with a greater risk of EG/EGS, supporting a etiologic role of ocular UV exposure on EG/EGS risk.
Keywords: 464 clinical (human) or epidemiologic studies: risk factor assessment •
463 clinical (human) or epidemiologic studies: prevalence/incidence •
461 clinical (human) or epidemiologic studies: natural history