Abstract 2591: Relationship Between Sunlight and Temperature Exposure to Stroke Incidence in the Reasons for Geographic and Racial Differences in Stroke (regards) Study
INTRODUCTION: Stroke incidence is higher during the winter, indicating that long and short-term sunlight exposure may contribute to stroke incidence.
HYPOTHESIS: Reduced sunlight exposure and extreme temperatures are associated with increased stroke incidence.
METHODS: Data were obtained from the REGARDS study, a national population-based cohort of 30,239 enrolled from 2003-2007 consisting of black and white participants, aged 45+. A centralized phone interview was used for medical history, in-home evaluation for physical measures, and a self-administered questionnaire for complete residential histories (city/state) from birth. The risk of stroke and sunlight exposure was studied in the 16,529 participants that were free of stroke and coronary artery disease at baseline and had lifetime residential histories available. Fifteen-year residential history merged with satellite and ground monitor data were used to determine sunlight and temperature exposure. Since long-term sunlight and temperature measures have not been extensively used in health studies, we performed exploratory analyses to determine which measures carried the strongest relationships with stroke. Fifteen, ten, five, two and one-year exposures were used to predict stroke incidence using Cox proportional hazard models. Potential demographic, behavioral, and medical confounders and mediators were included during model-building.
RESULTS: Over an average follow-up period of 5.0 years, 351 had an incident stroke. Monthly average sunlight and maximum temperature exposures at residence exhibited the strongest relationships with stroke. It was determined that the shortest period of sunlight exposure, one year, exhibited the strongest relationship. After adjustment for other covariates, the previous year’s monthly average sunlight exposure below the median predicted increased risk of stroke (HR=1.61 (95% CI: 1.15, 2.26)). Temperature exhibited a J-shaped relationship with stroke incidence.
CONCLUSION: This is the first report showing a relationship between sunlight and stroke. In addition, we confirmed earlier studies that both hot and cold temperatures are related to increased stroke incidence. The biological pathway of this relationship is not clear. Future research will show whether this finding stands, the pathway for this relationship, and if it is due to short or long-term exposures.
- © 2012 by American Heart Association, Inc.