Serum heavy metal levels increased in lung disease patients
medwireNews: Results from a large US study suggest that individuals with obstructive lung disease (OLD), particularly smokers, have significantly increased blood levels of cadmium and lead.
The team also found a significant inverse association between lung function and serum cadmium and lead concentrations among smokers.
In addition, the risk for OLD in smokers was attenuated after adjustment for serum cadmium levels, "suggesting that cadmium may mediate the association between smoking and OLD," say Shikhar Agarwal and Haala Rokadia from the Cleveland Clinic in Ohio.
The researchers studied a nationally representative sample of 9575 individuals who participated in the 2007-2008 and 2009-2010 National Health and Nutrition Examination Surveys. Of these, 12.4% tested positive for OLD, with a forced expiratory volume in 1 second [FEV1]/forced vital capacity ratio of less than 0.7.
"We chose to evaluate the OLD population as a whole, knowing that that population is a heterogeneous population that includes individuals with asthma as well as COPD [chronic obstructive pulmonary disease]," the researchers explain in Chest.
The prevalence of active and former smoking was significantly higher among participants with OLD than in those without, at 41.0% versus 26.7% and 29.8% versus 18.8%, respectively.
Blood samples collected from the participants revealed that those with OLD also had significantly higher mean serum concentrations of cadmium and lead than those without, at 0.51 versus 0.33 µg/L and 1.73 versus 1.18 µg/dL, respectively. Mean levels of serum cadmium and lead were particularly elevated in active smokers, at 1.04 and 2.01 µg/dL, respectively.
Furthermore, there was a significant dose-response association between increasing serum cadmium and lead concentrations and the risk for OLD. For example, participants in the highest decile of serum cadmium concentration were 2.52 times more likely to have OLD than those in the lowest decile. Similarly, participants in the highest decile for serum lead concentrations were 2.37 times more likely to have OLD than those in the lowest decile.
The risk for OLD was particularly high among active smokers compared with never smoker (odds ratio [OR]=3.3), but the association was attenuated after adjustment for serum cadmium level (OR=2.1). Adjustment for serum lead concentration did not have a significant effect on the risk for OLD.
The researchers also found that higher serum cadmium concentrations were associated with a lower percentage of predicted FEV1 values among smokers.
Agarwal and Rokadia conclude: "In a large representative sample of the US population, we demonstrated a significant association between OLD and serum cadmium and lead concentrations."
They suggest that "heavy metal exposure may contribute to increased oxidative stress and inflammation in the lungs, resulting in tissue destruction manifesting clinically as OLD."
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Mark Cowen, Senior medwireNews Reporter