Solar Exposure and Residential Geographic History in Relation to Exfoliation Syndrome in the United States and Israel

Abstract

IMPORTANCE Residential (geographic) history and extent of solar exposure may be important risk factors for exfoliation syndrome (XFS) but, to our knowledge, detailed lifetime solar exposure has not been previously evaluated in XFS.OBJECTIVE To assess the relation between residential history, solar exposure, and XFS. DESIGN, SETTING, AND PARTICIPANTSThis clinic-based case-control study was conducted in the United States and Israel. It involved XFS cases and control individuals (all Ն60-year-old white individuals) enrolled from 2010 to 2012 (United States: 118 cases and 106 control participants; Israel: 67 cases and 72 control participants). MAIN OUTCOMES AND MEASURESWeighted lifetime average latitude of residence and average number of hours per week spent outdoors as determined by validated questionnaires. RESULTSIn multivariable analyses, each degree of weighted lifetime average residential latitude away from the equator was associated with 11% increased odds of XFS (pooled odds ratio [OR], 1.11; 95% CI, 1.05-1.17; P < .001). Furthermore, every hour per week spent outdoors during the summer, averaged over a lifetime, was associated with 4% increased odds of XFS (pooled OR, 1.04; 95% CI, 1.00-1.07; P = .03). For every 1% of average lifetime summer time between 10 AM and 4 PM that sunglasses were worn, the odds of XFS decreased by 2% (OR, 0.98; 95% CI, 0.97-0.99; P < .001) in the United States but not in Israel (OR, 1.00; 95% CI, 0.99-1.01; P = .92; P for heterogeneity = .005). In the United States, after controlling for important environmental covariates, history of work over water or snow was associated with increased odds of XFS (OR, 3.86; 95% CI,); in Israel, there were too few people with such history for analysis. We did not identify an association between brimmed hat wear and XFS (P > .57). CONCLUSIONS AND RELEVANCELifetime outdoor activities may contribute to XFS. The association with work over snow or water and the lack of association with brimmed hat wear suggests that ocular exposure to light from reflective surfaces may be an important type of exposure in XFS etiology.

Nailfold capillary morphology in exfoliation syndrome

“…Moreover, the nailfold is largely unshielded from ambient solar exposure and it is known that ultraviolet radiation alters LOXL1 expression. 37 Perhaps interaction between ambient ultraviolet rays and LOXL1 activity 38,39 contributes to the nailfold capillary morphological changes we observed.…”

Exfoliation Syndrome and Solar Exposure

“…16, 20 However, LOXL1 SNPs are also detected in up to 88% of controls. 16 Additionally, the ratio of LOXL1 gene variants in those with XFS to those without XFS is similar in areas where the disease is prevalent 21,22 and in areas where the condition is uncommon. 13,21 This indicates that there are likely environmental factors that work to influence the development of XFS.…”

“…These studies found that lifetime and most recent residence in the northern tier of the United States (versus the middle and southern tiers) and with increasing latitude away from the equator are associated with increased risk of XFS. 14,21,31 Ambient low temperature, ambient solar exposure, time spent outdoors (particularly in youth), and leisure or work activity over water or snow are associated with elevated risk of XFS. 21,31,32 Sunglass, but not brimmed hat, wear decreases the risk of XFS.…”

“…14,21,31 Ambient low temperature, ambient solar exposure, time spent outdoors (particularly in youth), and leisure or work activity over water or snow are associated with elevated risk of XFS. 21,31,32 Sunglass, but not brimmed hat, wear decreases the risk of XFS. 21 …”

What have we learned about exfoliation syndrome since its discovery by John Lindberg 100 years ago?

“…This trend was also noted in the Nurses’ Health Study and Health Professionals Follow-up Study, where geographical residence in the middle or southern tiers of the USA was associated with a reduced risk of XFS compared with residence in the northern tier 12. Environmental factors such as solar irradiation and climatic variables are hypothesised to be responsible for the latitude effect 64. Ultraviolet radiation can upregulate the expression of LOXL1 as well as elastic fibre proteins found in exfoliation material 65.…”