Sunlight exposure and cardiovascular risk factors in the REGARDS study: a cross-sectional split-sample analysis
1 Department of Epidemiology, 1665 University Blvd, University of Alabama at Birmingham, Birmingham 35294, Alabama
2 Department of Medicine, University of Vermont College of Medicine, Burlington VT 05405, Canada
3 Department of Biostatistics, 1665 University Blvd, University of Alabama at Birmingham, Birmingham 35294, Alabama
4 National Space Science and Technology Center, NASA Marshall Space Flight Center, 320 Sparkman Drive, Huntsville 35805, Alabama
BMC Neurology 2014, 14:133 doi:10.1186/1471-2377-14-133Published: 19 June 2014
Previous research has suggested that vitamin D and sunlight are related to cardiovascular outcomes, but associations between sunlight and risk factors have not been investigated. We examined whether increased sunlight exposure was related to improved cardiovascular risk factor status.
Residential histories merged with satellite, ground monitor, and model reanalysis data were used to determine previous-year sunlight radiation exposure for 17,773 black and white participants aged 45+ from the US. Exploratory and confirmatory analyses were performed by randomly dividing the sample into halves. Logistic regression models were used to examine relationships with cardiovascular risk factors.
The lowest, compared to the highest quartile of insolation exposure was associated with lower high-density lipoprotein levels in adjusted exploratory (−2.7 mg/dL [95% confidence interval: −4.2, −1.2]) and confirmatory (−1.5 mg/dL [95% confidence interval: −3.0, −0.1]) models. The lowest, compared to the highest quartile of insolation exposure was associated with higher systolic blood pressure levels in unadjusted exploratory and confirmatory, as well as the adjusted exploratory model (2.3 mmHg [95% confidence interval: 0.8, 3.8]), but not the adjusted confirmatory model (1.6 mg/dL [95% confidence interval: −0.5, 3.7]).
The results of this study suggest that lower long-term sunlight exposure has an association with lower high-density lipoprotein levels. However, all associations were weak, thus it is not known if insolation may affect cardiovascular outcomes through these risk factors.