Abstract P045: Sun Exposure is Not Associated With Lower Cardiovascular Risk in Mexican Women

Abstract

Background: Sun exposure has been associated with reduced risk of stroke and all-cause mortality possibly due to a decreased vascular tone related to vitamin D production. However, previous studies have measured sun exposure based on geographical estimations of radiation, and have been mostly conducted in latitudes far from the Equator where UV radiation is lower than in tropical and subtropical latitudes and where there is little variation in skin tone. Hypothesis: Sun exposure is inversely associated with subclinical cardiovascular disease in Mexican women. Methods: We conducted a cross-sectional analysis in 2,257 disease-free women from the Mexican Teachers‘ Cohort who were invited to clinical examinations in 4 different Mexican states. Participants responded to questions on sun exposure habits at 4 age periods (12-24, 25-35, 36-59, >60). Sun exposure was defined as the weighted average of weekly hours spent under the solar noon from age 12 to the age at clinical examination. Carotid intima-media thickness (c-IMT) was measured on both carotid arteries through ultrasound by standardized neurologists and log transformed. We defined carotid atherosclerosis as mean right or left c-IMT ≥0.8 mm or the presence of plaque. We used linear and logistic regression to evaluate the association between quartiles of sun exposure, c-IMT and carotid atherosclerosis, with quartile 1 as reference. Results: Mean age of participants was 49.6 (5.5) years and the prevalence of carotid atherosclerosis was 12.3% in quartile 1 vs 10.6% in quartile 4. The median weekly hours of exposure for each quartile were: 1 (Q1), 1.79 (Q2), 3 (Q3), 4 (Q4). The age-adjusted % mean difference in c-IMT comparing women in the first quartile to women in the fourth quartile was -1.5% (95% CI -2.9, -0.1). After further adjustment for site, socioeconomic status, smoking status, ethnicity and physical activity the % mean difference was no longer significant (-0.7%, 95% CI -2.0, 0.7). The age-adjusted OR for carotid atherosclerosis for women in the fourth quartile compared to women in the first quartile was 0.81 (95% CI 0.57, 0.95). However, in the multivariable model, the OR was non-significant (0.94, 95% CI 0.69, 1.2). Stratified analysis for ethnicity and obesity showed no difference between groups. Conclusion: Sun exposure was associated with neither cIMT nor carotid atherosclerosis in Mexican women. Atherosclerosis might not play a role in the biological mechanism explaining the inverse association between sun exposure and cardiovascular risk.