No 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.

Background Previous studies have evaluated how sun exposure affects cardiovascular health. In this sense, some evidence from ecological studies have found an inverse relationship between sun exposure and blood pressure or CVD. The aim of this study is to determine whether long-term sun exposure has a protective role in subclinical cardiovascular disease in adult Mexican women. Methods We conducted a cross-sectional analysis of a sample of women from the Mexican Teachers’ Cohort (MTC) study. Sun exposure was assessed in the MTC 2008 baseline questionnaire, in which women were asked about their sun-related behavior. Vascular neurologists measured carotid intima-media thickness (IMT) using standard techniques. Multivariate linear regression models were used to estimate the percentage difference in mean IMT and 95% confidence intervals (95% CIs), according to categories of sun exposure and multivariate logistic regression models were used to estimate the odds ratio (OR) and 95% CIs for carotid atherosclerosis. Results The mean age of participants was 49.6 ± 5.5 years, the mean IMT was 0.678 ± 0.097 mm, and the mean accumulated hours of weekly sun exposure were 2.9 ± 1.9. Prevalence of carotid atherosclerosis was 20.9%. Compared to women in the lowest category of sun exposure, the multivariate adjusted ORs of carotid atherosclerosis were 0.54 (95%CI: 0.24, 1.18) for women who were exposed 9 hours. For women who denied regular sun screen use, those in the higher exposure category (9 hours) had lower mean IMT compared to those in the lower category (multivariable-adjusted mean % difference = -2.67; 95%CI: -6.9, -1.5). Conclusion In general, we observed that cumulative sun exposure was inversely associated with IMT and subclinical carotid atherosclerosis. Our findings suggest that public health messages should also consider the sun’s positive role for health, while still emphasizing the negative impacts of excessive exposure.