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Past exposure to sun, skin phenotype, and risk of multiple sclerosis: case-control study

BMJ 2003; 327 doi: https://doi.org/10.1136/bmj.327.7410.316 (Published 07 August 2003) Cite this as: BMJ 2003;327:316
  1. I A F van der Mei, PhD student1 (Ingrid.vanderMei{at}utas.edu.au),
  2. A-L Ponsonby, associate professor2,
  3. T Dwyer, professor1,
  4. L Blizzard, biostatistician1,
  5. R Simmons, principal research fellow3,
  6. B V Taylor, neurologist4,
  7. H Butzkueven, neurologist5,
  8. T Kilpatrick, associate professor5
  1. 1Menzies Centre for Population Health Research, University of Tasmania, Hobart, TAS 7000, Australia
  2. 2National Centre for Epidemiology and Population Health, Australian National University, Canberra, Australia
  3. 3Australian MS Longitudinal Study, Canberra Hospital, Canberra, Australia
  4. 4Royal Hobart Hospital, Hobart, Australia
  5. 5Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
  1. Correspondence to: I A F van der Mei
  • Accepted 3 June 2003

Abstract

Objective To examine whether past high sun exposure is associated with a reduced risk of multiple sclerosis.

Design Population based case-control study.

Setting Tasmania, latitudes 41-3°S.

Participants 136 cases with multiple sclerosis and 272 controls randomly drawn from the community and matched on sex and year of birth.

Main outcome measure Multiple sclerosis defined by both clinical and magnetic resonance imaging criteria.

Results Higher sun exposure when aged 6-15 years (average 2-3 hours or more a day in summer during weekends and holidays) was associated with a decreased risk of multiple sclerosis (adjusted odds ratio 0.31, 95% confidence interval 0.16 to 0.59). Higher exposure in winter seemed more important than higher exposure in summer. Greater actinic damage was also independently associated with a decreased risk of multiple sclerosis (0.32, 0.11 to 0.88 for grades 4-6 disease). A dose-response relation was observed between multiple sclerosis and decreasing sun exposure when aged 6-15 years and with actinic damage.

Conclusion Higher sun exposure during childhood and early adolescence is associated with a reduced risk of multiple sclerosis. Insufficient ultraviolet radiation may therefore influence the development of multiple sclerosis.

Footnotes

  • Contributors A-LP, TD, and RS designed the study. IvdM coordinated the study and TK, HB, and BVT were the neurologists responsible for the clinical diagnosis of the cases. IvdM conducted the statistical analysis in conjunction with A-LP, LB, and TD. The main contributors to the writing of the report were IvdM, A-LP, LB, and TD, but others provided important feedback at a later stage. All authors approved the final document.

  • Funding This project was supported with funding from the National Health and Research Council of Australia, the Australian Rotary Health Research Fund, and MS Australia. IvdM is supported by the Cooperative Research Centre for Discovery of Genes for Common Human Diseases (gene-CRC), and TK is a Viertel fellow. The gene-CRC was established and is supported by the Australian government's Cooperative Research Centre's programme. The guarantor accepts full responsibility for the conduct of the study, had access to the data, and controlled the decision to publish

  • Competing interests None declared

  • Ethical approval The project was approved by the human research ethics committee of the Royal Hobart Hospital.

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