Smoking's Impact on Selenium Levels & Mortality Rates in US Adults

The role of selenium in human health has been an area of significant interest among researchers, particularly its impact on mortality rates due to specific diseases. A recent study involving American adults recorded a total of 837 fatalities up to December 31, 2019. Among these deaths, cardiovascular disease (CVD) claimed the lives of 252 individuals, cancer took another 179 lives, and non-cardiovascular diseases caused the remaining fatalities. 
 
In this prospective study, serum selenium concentration was examined for possible links with mortality related to cardiovascular disease and cancer. The Cox proportional hazards models were used in this analysis after adjusting for multiple variables. These complex models revealed a statistically significant association between serum selenium levels and CVD-related as well as cancer-related mortalities. 
 
Selenium is an essential trace mineral that plays a vital role in many biological functions, including immunity and fertility. In our bodies, it acts as an antioxidant, helping prevent cell damage from free radicals, which are produced by normal body processes such as metabolism or exposure to environmental toxins like smoke or radiation. 
 
Specifically, the risk of death from CVD decreased by approximately three quarters for each unit increase in logarithmically converted serum selenium concentration, while the risk reduction was even more pronounced at around four-fifths for cancer mortalities. 
 
These findings suggest that appropriate levels of serum selenium can significantly decrease all-cause mortality rates, along with those attributed specifically to CVDs or cancers, thereby underscoring its importance in maintaining good health. 
 
However, dividing participants into quartiles based on their serum selenium concentrations revealed some interesting patterns; compared with individuals in the lowest quartile (< 119.9 μg/L), those belonging to higher quartiles had lower all-cause mortality rates along with reduced deaths due specifically to either CVDs or cancers depending upon their respective quartile classification. 
 
Notably, once blood selenium content exceeded certain thresholds, i.e., ≥ 129.82 μg/L for all-cause and non-CVD-related mortalities or ≥ 129.08 μg/L for CVD deaths, the protective effect was no longer observed, which suggests a nonlinear relationship between serum selenium concentrations and these specific mortality rates. 
 
Subgroup analyses further identified significant interactions between serum selenium levels and factors such as age, sex, smoking status, etc., with respect to all-cause mortality. For instance, among males who were current smokers or had moderate income levels without any history of high cholesterol or stroke, higher selenium levels were associated with lower all-cause death rates. 
 
Conversely, when the blood selenium concentration exceeded 129.82 μg/L in nonsmokers, there was no association found between this trace mineral's level and cause-specific mortality rates, whereas an increase in overall death risk was seen among current smokers, suggesting that beyond certain thresholds even essential nutrients like selenium can potentially have adverse health effects, particularly if combined with harmful lifestyle choices such as smoking. 
 
The findings from this study underscore not only the importance of maintaining optimal serum selenium concentrations but also highlight potential risks associated with excessive intake, especially among certain subpopulations, thereby emphasizing the need for careful monitoring during supplementation while considering individual variability, including regional dietary habits and lifestyle choices. 
 
While more research is needed to fully understand the complex relationships between serum selenium levels, various diseases, and overall mortality rates, these results provide important insights into how this essential trace mineral may help reduce disease burdens while improving public health outcomes at the population level given its significant role in many biological functions critical for human health.