244649 Use of ground and satellite data to determine the relationship between long-term sunlight exposure and stroke incidence in the REasons for Geographic and Racial Differences in Stroke (REGARDS) Study

Monday, October 31, 2011: 3:06 PM

Shia Kent, MSPH , Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL
     
Background Stroke incidence varies with climate conditions, possibly indicating that sunlight affects cerebrovascular health through cutaneous vitamin D production or circadian rhythm pathways

Objectives We tested two hypotheses: (1) whether ground and satellite measures of long-term insolation are associated with stroke incidence, and (2) whether the relationship between sunlight and incident stroke differs by sex, age, socioeconomic variables, or activity levels.

Methods We performed longitudinal analyses in a cohort of 16.771 black and white participants 45 years or older. We captured sunlight exposure as the daily insolation received at the participant's self-reported residences for 15 years previous to baseline. In these exploratory analyses, we characterized sunlight and temperature using several methods and time periods. Analyses used Cox proportional hazards and used time to first stroke as the outcome. We controlled for numerous possible demographic, behavioral, and medical confounders.

Results Sunlight exposures during the year previous to the start of follow-up had stronger relationships with stroke than longer time periods. Environmental exposures at baseline were characterized as the monthly averages of insolation and maximum temperatures for the year previous to the start of follow-up. The hazard ratio for the 4th quartile of insolation compared to the 1st quartile, after accounting for all confounders, was 1.6 (95% CI: 1.1, 2.2). The hazard ratio for the 4th quartile of temperature compared to the 2nd quartile, after accounting for all confounders, was 1.8 (95% CI: 1.2, 2.8). No significant interactions were detected.

Conclusions The innovative method of combining a ground and satellite-based dataset with individual participants' residential histories to create long-term environmental exposure estimates was used to explore health relationships. This paper is the first to indicate that not only temperature, but also sunlight exposure may have a relationship with stroke.

Learning Areas:
Chronic disease management and prevention
Environmental health sciences
Epidemiology

Learning Objectives:
(1) Demonstrate an innovative method of using satellite data and residential histories to measure individual's environmental exposures. (2) Analyze the previously unexplored hypothesis that sunlight exposure may have a relationship with stroke. (3) Discuss the implications of longer vs. shorter tem exposure to sunlight on stroke risk.

Keywords: Environmental Health, Strokes

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: This is part of my dissertation. I was part of idea origination, and I performed the analyses and wrote the abstract.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.

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