Sun exposure and intima-media thickness in the Mexican Teachers' Cohort

Abstract

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.