title: A proposed methodology to estimate the cumulative life-time UVB exposure using geographic information systems: An application to multiple sclerosis.
abstract: BACKGROUND
  The cause of multiple sclerosis (MS) is unknown; multiple risk factors have been implicated, including environmental exposures, such as sunlight. Many studies have relied on latitude alone as a crude proxy for sunlight exposure. We aimed to develop a protocol allowing a more detailed estimate of cumulative ambient ultra-violet B (UVB) exposure at critical time-periods over a patient's life-course.
  
  
  METHODS
  4010 definite MS patients with a 'movement history' from birth to the study end (2005) were selected from the University of British Columbia, Canada's MS Genetic database. Patient's place of resident from birth were tracked, each place being geocoded (latitude and longitude) and assigned a UVB value using the NASA Total Ozone Mapping Spectrometer (TOMS) dataset. Combined, these data allowed an estimated UVB value for each patient based on year and location.
  
  
  RESULTS
  Using this protocol, we provide a potentially more detailed cumulative UVB exposure for critical periods in a patients' life history based on their individual spatial migration through time.
  
  
  CONCLUSIONS
  This protocol is intended to provide a framework for researchers to more accurately estimate UVB exposures for individuals over the course of their life history and may be useful for understanding etiology of MS and other chronic disease.
authors: Department of Geography, Simon Fraser University, Canada.
authors: N
authors: N
authors: Schuurman
authors: Department of Geography, Simon Fraser University, Canada.
authors: O
authors: O
authors: Amram
authors: National Neuroscience Institute, King Fahad Medical City, Riyadh, Kingdom of Saudi Arabia.
authors: J
authors: J
authors: Saeedi
authors: Department of Neurology, Sozialstiftung Bamberg Hospital, Bamberg, Germany.
authors: P
authors: P
authors: Rieckmann
authors: Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
authors: I
authors: I
authors: Yee
authors: Faculty of Medicine, Division of Neurology, Multiple Sclerosis Program and Brain Research Centre, Vancouver Coastal health Research Institute, University of British Columbia, Vancouver, Canada. Electronic address: helen.tremlett@ubc.ca.
authors: H
authors: H
authors: Tremlett
keywords: Ecological study; Geographic Information Systems (GIS); Methodological study; Multiple sclerosis; NASA Total Ozone Mapping Spectrometer; Ultraviolet B exposure