title: Low Serum 25-Hydroxyvitamin D Levels Are Associated with Dry Eye Syndrome.
abstract: BACKGROUND
  Dry eye syndrome (DES) is a common tear film and ocular surface disease that results in discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. Systemic diseases associated with DES include diabetes mellitus, rheumatoid arthritis, depression, anxiety, thyroid disease, allergic diseases, irritable bowel syndrome, chronic pain syndrome, and hyperlipidemia. Interestingly, it has been found that most of these are associated with low levels of serum 25-hydroxyvitamin D (25(OH)D) or inadequate sunlight exposure.
  
  
  METHODS
  In this cross-sectional data analysis, noninstitutionalized adults aged ≥19 years (N = 17,542) who participated in Korean National Health and Nutrition Examination Survey 2010-2012 were included. Information regarding duration of sunlight exposure was collected from the survey participants. Serum 25(OH)D and zinc levels were measured. The confounding variables were age, gender, sunlight exposure time, region of residence, obesity, serum 25(OH)D level, diabetes mellitus, rheumatoid arthritis, depression, thyroid disorder, atopic dermatitis, history of ocular surgery, regular exercise, and walking exercise.
  
  
  RESULTS
  Mean serum 25(OH)D levels of subjects with and without DES were 16.90 ± 6.0 and 17.52 ± 6.07 (p<0.001). Inadequate sunlight exposure time (odds ratio [OR], 1.554; 95% confidence interval [CI], 1.307-1.848), urban residence (OR, 1.669; 95% CI, 1.456-1.913), indoor occupation (OR, 1.578; 95% CI, 1.389-1.814), and low serum 25(OH)D level (OR, 1.158; 95% CI, 1.026-1.308) were the risk factors for DES. After adjusting for age, sex, obesity, diabetes mellitus, rheumatoid arthritis, depression, thyroid disorder, atopic dermatitis, history of ocular surgery, regular exercise, and occupation, low serum 25(OH)D level (OR, 1.178; 95% CI, 1.010-1.372) and deficient sunlight exposure time (OR, 1.383; 95% CI, 1.094-1.749) were the risk factors for diagnosed DES.
  
  
  CONCLUSIONS
  Low serum 25(OH)D levels and inadequate sunlight exposure are associated with DES in Korean adults. These results suggest that sufficient sunlight exposure or vitamin D supplementation may be useful in DES treatment.
authors.affiliation: Department of Ophthalmology, Hallym University College of Medicine, Seoul, Republic of Korea.
authors.forename: Sam Young
authors.initials: SY
authors.lastname: Yoon
authors.affiliation: Department of Ophthalmology, Hallym University College of Medicine, Seoul, Republic of Korea.
authors.forename: Seok Hyun
authors.initials: SH
authors.lastname: Bae
authors.affiliation: Department of Ophthalmology, Hallym University College of Medicine, Seoul, Republic of Korea.
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Shin
authors.affiliation: Department of Occupational and Environmental Medicine, Inha University School of Medicine, Incheon, Republic of Korea.
authors.forename: Shin Goo
authors.initials: SG
authors.lastname: Park
authors.affiliation: Department of Dentistry, Keimyung University School of Medicine, Daegu, Republic of Korea.
authors.forename: Sang-Hee
authors.initials: SH
authors.lastname: Hwang
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Republic of Korea.|Department of Ophthalmology, Seoul National University Bundang Hospital, Seongnam, Gyeonggi, Korea.
authors.forename: Joon Young
authors.initials: JY
authors.lastname: Hyon
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Won Ryang
authors.initials: WR
authors.lastname: Wee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D015352:Dry Eye Syndromes / Q000097:blood*; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013472:Sunlight; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D055815:Young Adult
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D