More sun when young, less myopia when old – Jan 2017

Association Between Myopia, Ultraviolet B Radiation Exposure, Serum Vitamin D

Concentrations, and Genetic Polymorphisms in Vitamin D Metabolic Pathways in a Multicountry European Study.
JAMA Ophthalmol. 2017 Jan 1;135(1):47-53. doi: 10.1001/jamaophthalmol.2016.4752.

Williams KM1, Bentham GC2, Young IS3, McGinty A3, McKay GJ3, Hogg R4, Hammond CJ5, Chakravarthy U4, Rahu M6, Seland J7, Soubrane G8, Tomazzoli L9, Topouzis F10, Fletcher AE11.

• 1Department of Ophthalmology, King's College London, London, United Kingdom
• 2Department of Twin Research and Genetic Epidemiology, King's College London, London, United Kingdom.
• 2School of Environmental Sciences, University of East Anglia, East Anglia, United Kingdom.
• 3Centre for Public Health, Queen's University Belfast, Belfast, United Kingdom.
• 4Centre for Experimental Medicine, Institute of Clinical Science, Queen's University Belfast, Belfast, United Kingdom.
• 5Department of Ophthalmology, King's College London, London, United Kingdom.
• 6Department of Epidemiology and Biostatistics, National Institute for Health Development, Tallinn, Estonia.
• 7Eye Department, University of Bergen, Bergen, Norway.
• 8Department of Ophthalmology, Hôtel-Dieu de Paris, Paris Descartes University, Paris, France.
• 9Ophthalmology Clinic, University of Verona, Verona, Italy.
• 10Department of Ophthalmology, Aristotle University of Thessaloniki School of Medicine, Thessaloniki, Greece.
• 11Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.

IMPORTANCE:
Myopia is becoming increasingly common globally and is associated with potentially sight-threatening complications. Spending time outdoors is protective, but the mechanism underlying this association is poorly understood.

OBJECTIVE:
To examine the association of myopia with ultraviolet B radiation (UVB; directly associated with time outdoors and sunlight exposure), serum vitamin D concentrations, and vitamin D pathway genetic variants, adjusting for years in education.

DESIGN, SETTING, AND PARTICIPANTS:
A cross-sectional, population-based random sample of participants 65 years and older was chosen from 6 study centers from the European Eye Study between November 6, 2000, to November 15, 2002. Of 4187 participants, 4166 attended an eye examination including refraction, gave a blood sample, and were interviewed by trained fieldworkers using a structured questionnaire. Myopia was defined as a mean spherical equivalent of -0.75 diopters or less. Exclusion criteria included aphakia, pseudophakia, late age-related macular degeneration, and vision impairment due to cataract, resulting in 371 participants with myopia and 2797 without.

EXPOSURES:
Exposure to UVB estimated by combining meteorological and questionnaire data at different ages, single-nucleotide polymorphisms in vitamin D metabolic pathway genes, serum vitamin D3 concentrations, and years of education.

MAIN OUTCOMES AND MEASURES:
Odds ratios (ORs) of UVB, serum vitamin D3 concentrations, vitamin D single-nucleotide polymorphisms, and myopia estimated from logistic regression.

RESULT:
Of the included 3168 participants, the mean (SD) age was 72.4 (5) years, and 1456 (46.0%) were male.
An SD increase in UVB exposure at age

• 14 to 19 years (OR, 0.81; 95% CI, 0.71-0.92) and
• 20 to 39 years (OR, 0.7; 95% CI, 0.62-0.93)

was associated with a reduced adjusted OR of myopia; those in the highest tertile of years of education had twice the OR of myopia (OR, 2.08; 95% CI, 1.41-3.06). No independent associations between myopia and serum vitamin D3 concentrations nor variants in genes associated with vitamin D metabolism were found.
An unexpected finding was that the highest quintile of plasma lutein concentrations was associated with a reduced OR of myopia (OR, 0.57; 95% CI, 0.46-0.72).

CONCLUSIONS AND RELEVANCE:
Increased UVB exposure was associated with reduced myopia, particularly in adolescence and young adulthood. The association was not altered by adjusting for education. We found no convincing evidence for a direct role of vitamin D in myopia risk. The relationship between high plasma lutein concentrations and a lower risk of myopia requires replication.

PMID: 27918775 DOI: 10.1001/jamaophthalmol.2016.4752

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