Poster or Presentation Title
Advisor(s)
Qin Qin
Subjects
Biology
Abstract
Introduction: As the use of cell phones have increased immensely in the last two decades, so has public concern regarding cell phone and its relationship to cancer. Cell phones emit radio frequency waves, a type of electromagnetic energy. Theoretically, these radiofrequency waves are considered as a form of non-ionizing radiation, and do not contain enough energy to damage DNA. However, human and animal studies on cell phone use and cancer risk have shown mixed results. The Danish cohort study, one of the largest long-term studies to date, compared everyone in Denmark with cell phone subscriptions between 1982 and 1995, and found no evidence of increased risk in brain or other nervous system tumors in cell phone users. After we analyzed the Danish cohort study, we found several limitations that brought the conclusion of this study into question. We hypothesized that cell phones may still be associated with increased cancer risks.
Materials and Methods: We reanalyzed data from the Danish cohort study. Data as reported from the Danish cohort were used. The overall significant level was 0.025 (1-sided). The simulation method by R was applied to estimate statistical power from the Danish data. The sample sizes for the future studies were also evaluated using the simulation method based on appropriate study power.
Results: Data from the Danish cohort study included 420,095 cell phone users in Denmark with an average of an 8.5-year follow-up. The observed overall cancer and brain tumor incidences were 420.10 and 16.24 per 100,000 personal years respectively. Comparing expected cancer incidences (overall=399.04 and brain tumor=16.80 per 100,000 personal years); there were no statistically significant changes. We further estimated the statistical power to detect an increase in cancer risk from the Danish data. The Danish data had more than 95% and 99% power to detect 3% and 5% increase in overall cancer risk. But it had very low power to detect an increase in brain tumor risk; it had only 11% and 23% power to detect a 3% and 5% increase in brain tumor risk respectively. The statistical power in Danish data would increase more than 80% and 90% if the brain tumor risk increased 12% and 15% respectively. Furthermore, we explored the appropriate power for future studies. Our results indicated a cohort study with 80% power needs at least 20,000,000 and 5,000,000 personal years for follow-up to detect 5% and 10% increase in brain tumor risk respectively.
Conclusion: Our simulation results found that there was enough power to detect more than 3% increase in overall cancer risk and confirmed that there was no association between overall cancer risk and cell phone use. But the Danish data had little power to detect any less than 5% increase in brain tumor risk associated with cell phone use. Therefore, there was insufficient evidence to suggest that there was no increased risk in brain tumor associated with cell phone use. Future studies with either a larger population or longer follow-up times should be conducted to elucidate the relationship between cell phone and brain tumor risk.
Included in
Cellphone Usage and the Risk of Cancer
Introduction: As the use of cell phones have increased immensely in the last two decades, so has public concern regarding cell phone and its relationship to cancer. Cell phones emit radio frequency waves, a type of electromagnetic energy. Theoretically, these radiofrequency waves are considered as a form of non-ionizing radiation, and do not contain enough energy to damage DNA. However, human and animal studies on cell phone use and cancer risk have shown mixed results. The Danish cohort study, one of the largest long-term studies to date, compared everyone in Denmark with cell phone subscriptions between 1982 and 1995, and found no evidence of increased risk in brain or other nervous system tumors in cell phone users. After we analyzed the Danish cohort study, we found several limitations that brought the conclusion of this study into question. We hypothesized that cell phones may still be associated with increased cancer risks.
Materials and Methods: We reanalyzed data from the Danish cohort study. Data as reported from the Danish cohort were used. The overall significant level was 0.025 (1-sided). The simulation method by R was applied to estimate statistical power from the Danish data. The sample sizes for the future studies were also evaluated using the simulation method based on appropriate study power.
Results: Data from the Danish cohort study included 420,095 cell phone users in Denmark with an average of an 8.5-year follow-up. The observed overall cancer and brain tumor incidences were 420.10 and 16.24 per 100,000 personal years respectively. Comparing expected cancer incidences (overall=399.04 and brain tumor=16.80 per 100,000 personal years); there were no statistically significant changes. We further estimated the statistical power to detect an increase in cancer risk from the Danish data. The Danish data had more than 95% and 99% power to detect 3% and 5% increase in overall cancer risk. But it had very low power to detect an increase in brain tumor risk; it had only 11% and 23% power to detect a 3% and 5% increase in brain tumor risk respectively. The statistical power in Danish data would increase more than 80% and 90% if the brain tumor risk increased 12% and 15% respectively. Furthermore, we explored the appropriate power for future studies. Our results indicated a cohort study with 80% power needs at least 20,000,000 and 5,000,000 personal years for follow-up to detect 5% and 10% increase in brain tumor risk respectively.
Conclusion: Our simulation results found that there was enough power to detect more than 3% increase in overall cancer risk and confirmed that there was no association between overall cancer risk and cell phone use. But the Danish data had little power to detect any less than 5% increase in brain tumor risk associated with cell phone use. Therefore, there was insufficient evidence to suggest that there was no increased risk in brain tumor associated with cell phone use. Future studies with either a larger population or longer follow-up times should be conducted to elucidate the relationship between cell phone and brain tumor risk.