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Research: STRAM and colleagues,
Listed in Issue 79
Abstract
STRAM and colleagues, Department of Preventive Medicine, School of Medicine, University of Southern California, Los Angeles, CA 90033, USA, stram@rcf.usc.edu, investigated whether biases in (self-reported) assessment of smoking may account for the observed apparent protective effect of high beta-carotene levels against lung cancer .
Background
Results from population studies suggest that there is a reduced risk of lung cancer among smokers who consume higher levels or who have higher blood levels of beta-carotene . However, the results from three randomized clinical trials, which investigated the effects of beta-carotene supplementation on the incidence of lung cancer in smokers, have not confirmed these epidemiological findings. A further problem is that tobacco use is associated with low intake or low blood levels of beta-carotene . In addition, data on smoking (frequency and history) derived from self-reports can be highly variable and inaccurate .
Methodology
The researchers developed a statistical model for random errors in reported smoking relative to true tobacco exposure and assumed a modest negative relationship between true tobacco exposure and blood levels of beta-carotene. The researchers combined their calculations from this model with those from a model for lung cancer (Doll and Peto, J Epidemiol Community Health 1978; 78: 303-13).
Results
Resulting calculations suggested that assessment biases of smoking exposure in smokers with low versus high beta-carotene intake could reasonably explain much or all of the apparent protective effect of high beta-carotene levels against lung cancer.
Conclusion
Studies of lung cancer in smokers are needed that employ measurements of biomarkers of smoking . The researchers report that such studies are currently underway.
References
Stram DO et al. Is residual confounding a reasonable explanation for the apparent protective effects of beta-carotene found in epidemiological studies of lung cancer in smokers? American Journal of Epidemiology 155 (7): 622-8. Apr 2002.
