Relationship between sun exposure and cardiovascular disease: Results from the NHANES and Mendelian randomization study

There is a growing interest in the health benefits of sun exposure, yet evidence linking sun exposure to cardiovascular disease (CVD) risk is limited. This study aimed to investigate the associations between sun exposure and CVD. This study utilized data from the National Health and Nutrition Examination Survey (NHANES), assessing sun exposure through behaviors such as staying in the shade, wearing long-sleeved shirts, using sunscreen, and time spent outdoors on weekdays and non-workdays. CVD was defined by self-reported physician-diagnosed heart disease (including congestive heart failure, coronary heart disease, angina, heart attack, and stroke). Multivariate logistic regression was applied. A bidirectional two-sample Mendelian randomization (MR) was also conducted to assess the causal relationship. Effect sizes were expressed as odds ratios (ORs) with a 95% confidence interval (CI). The study showed that staying less in shade decreased the risk of CVD (never in model 3: OR = 0.72, 95% CI= 0.54-0.96, p = 0.03). Additionally, CVD was influenced by using sunscreen (always in model 3: OR = 0.69, 95% CI= 0.50-0.94, p = 0.02) and spending time outdoors (model 3: OR = 0.96, 95% CI= 0.93-0.99, p = 0.01). Wearing long-sleeved shirts did not affect on the occurrence of CVD. However, no evidence of a causal relationship between sun exposure and CVD using MR analysis was observed. While the NHANES data suggested sun exposure was associated with a reduced risk of CVD, the MR analysis did not establish a causal link, suggesting further research is needed to understand this relationship.