Epidemiology • Volume 25, Number 4, July 2014
Letters
TABLE. Associations of Salt Habits with Cancer Deaths in 17,733 Men and Women ≥16 Years of Age Basic Modela RR (95% CI) Adding salt to prepared meals Never 1.00 Occasionally 1.12 (0.99–1.27) Always 1.30 (1.04–1.62)
Basic Model + Smokingb RR (95% CI)
Basic Model + BMIc RR (95% CI)
Basic Model + Smoking + BMId RR (95% CI)
1.00 1.07 (0.95–1.21) 1.16 (0.93–1.45)
1.00 1.14 (1.00–1.28) 1.31 (1.05–1.63)
1.00 1.09 (0.96–1.23) 1.17 (0.94–1.47)
a
Adjusted for age, sex, and study wave. Additionally adjusted for smoking (never, former, and number of cigarettes). c Additionally adjusted for BMI. d Adjusted for all variables. b
for smoking substantially weakened this association, while adjustment for BMI had virtually no impact. In this general population sample from Switzerland, there was a doseresponse association between adding salt to a prepared meal and the risk of death from cancer. To some extent, this association was confounded by smoking. People who smoke may have a higher taste threshold than those who do not.2 Smokers may also differ in their health behavior patterns, including less attention to a healthy diet.6 Both salt sensitivity and eating patterns could also vary between normal weight and overweight people,3 although BMI did not appear to confound the salt-mortality association in our data. Our analysis was limited by the fact that salt habits and smoking were self-reported and assessed only once, at baseline. In addition, cancer-specific analyses were not possible due to relatively small number of cancer deaths.
REFERENCES 1. D’Elia L, Rossi G, Ippolito R, Cappuccio FP, Strazzullo P. Habitual salt intake and risk of gastric cancer: a meta-analysis of prospective studies. Clin Nutr. 2012;31:489–498. 2. Pavlos P, Vasilios N, Antonia A, Dimitrios K, Georgios K, Georgios A. Evaluation of young smokers and non-smokers with electrogustometry and contact endoscopy. BMC Ear Nose Throat Disord. 2009;9:9. 3. Pepino MY, Mennella JA. Cigarette smoking and obesity are associated with decreased fat perception in women. Obesity (Silver Spring). 2014;22:1050–1055. 4. Bopp M, Braun J, Faeh D, Gutzwiller F; Swiss National Cohort Study Group. Establishing a follow-up of the Swiss MONICA participants (1984-1993): record linkage with census and mortality data. BMC Public Health. 2010;10:562. 5. Bopp M, Braun J, Gutzwiller F, Faeh D; Swiss National Cohort Study Group. Health risk or resource? Gradual and independent association between self-rated health and mortality persists over 30 years. PLoS One. 2012;7:e30795. 6. Moreno-Gómez C, Romaguera-Bosch D, Tauler-Riera P, et al. Clustering of lifestyle factors in Spanish university students: the relationship between smoking, alcohol consumption, physical activity and diet quality. Public Health Nutr. 2012;15:2131–2139.
ACKNOWLEDGMENTS We thank Dr. Kelly Turner for proof reading. We thank the Swiss Federal Statistical Office for providing mortality and census data. David Faeh Sabine Rohrmann Milo Puhan Julia Braun Institute of Social and Preventive Medicine (ISPM) University of Zurich Zurich, Switzerland [email protected] 616 | www.epidem.com
Mobile Phones and Cancer Next Steps
To the Editor: amet and colleagues1 present the state of knowledge on mobile phones and cancer 2 years after the International
S
Copyright © 2014 by Lippincott Williams & Wilkins ISSN: 1044-3983/14/2504-0616 DOI: 10.1097/EDE.0000000000000118
Agency for Research on Cancer evaluation of radiofrequency radiation,2 which recommended a coordinated, strategic plan of epidemiologic research, experimental studies, and risk communication and management. Samet and colleagues1 describe results of recent epidemiologic studies, including analysis of data from 5 INTERPHONE countries using estimates of cumulative energy at tumor location.3 They report the increased glioma risk among heaviest users but omit important findings: a dose-response for glioma among long-term users and, in case-only analyses minimizing recall bias by ignoring reported amount and laterality of use, an increased odds ratio (OR) among longterm users in the most exposed part of the brain.3 They also do not mention a similar OR in case-specular analyses of data from 7 other INTERPHONE countries.4 Recommendations stemming from previous case-control studies include the following: (1) further development of radiofrequency radiation exposure modeling, (2) bias modeling, and (3) parallel reanalysis of the INTERPHONE and Hardell studies. We fully support such recommendations. Despite limitations of the case-control design—which must be addressed—this design is the most powerful for investigating potential associations between radiofrequency radiation and brain tumors. Prospective studies based on operator records are also recommended; although immune to recall bias, they are limited by statistical power (INTERPHONE captured a population of 50 million, hardly achievable in a cohort study), exposure assessment, and selection bias. Time-trend analyses are important for population surveillance but have limited power to detect risks of tumors arising only in the most exposed part of the brain, years after substantial exposure.2 Samet and colleagues1 also note the importance of developing and implementing a strategic research agenda and keeping the public well informed. The newly European Union–funded GERoNiMO project (geronimo.crealradiation.com) builds upon existing European resources (including large-scale © 2014 Lippincott Williams & Wilkins
Epidemiology • Volume 25, Number 4, July 2014 Letters
cohort and case-control studies) to: (1) better understand health effects (and mechanisms) potentially associated with electromagnetic fields (EMF), including brain tumors, neurodegenerative, behavioral, and reproductive outcomes; (2) better characterize EMF exposure in the general population; (3) improve integration of EMF and health research into health risk assessment; and (4) underpin risk management policies. GERoNiMO focuses on radiofrequency radiation (from mobile phones and newer communication technologies) and increasingly ubiquitous intermediate frequency fields—alone and in combination with other environmental exposures. We anticipate that GERoNiMO will improve the integration, coherence, and coordination of EMF and health research, leading to improved evidence-based risk estimation, management, and communication. Chelsea Eastman Langer James Grellier Michelle C. Turner Elisabeth Cardis Radiation Programme Centre for Research in Environmental Epidemiology (CREAL) Barcelona, Spain Universitat Pompeu Fabra (UPF) Barcelona, Spain Ciber Epidemiología y Salud Pública (CIBERESP) Madrid, Spain [email protected]
REFERENCES 1. Samet JM, Straif K, Schüz J, Saracci R. Commentary: Mobile Phones and Cancer: Next Steps After the 2011 IARC Review. Epidemiology. 2014;25:23–27. 2. Baan R, Grosse Y, Lauby-Secretan B, et al; WHO International Agency for Research on Cancer Monograph Working Group. Carcinogenicity of radiofrequency electromagnetic fields. Lancet Oncol. 2011;12: 624–626. 3. Cardis E, Armstrong BK, Bowman JD, et al. Risk of brain tumours in relation to estimated RF dose from mobile phones: results from five Interphone countries. Occup Environ Med. 2011;68:631–640. 4. Larjavaara S, Schüz J, Swerdlow A, et al. Location of gliomas in relation to mobile telephone use: a case-case and case-specular analysis. Am J Epidemiol. 2011;174:2–11.
© 2014 Lippincott Williams & Wilkins
Mobile Phones and Cancer Next Steps To the Editors: e welcome the commentary by Samet et al1 and their recommendation for reanalysis of the main case-control studies on radiofrequency electromagnetic fields (the basis of all wireless technology). This reanalysis is something we have also suggested. The authors discuss pros and cons for the IARC classification of radiofrequency electromagnetic fields as “possibly carcinogenic to humans” (group 2B). However, several more recently published articles are either misinterpreted in or omitted from their presentation— for instance, 3 articles published by our research group on meningioma,2 acoustic neuroma,3 and malignant brain tumors.4 Our study and the INTERPHONE study differ in their recruitment of cases and controls, participation rates, and assessment of exposure, but restricting to the same age groups and omitting the use of cordless phones (as in INTERPHONE) gives similar results.5 The Danish cohort study6 was included in the IARC evaluation of radiofrequency electromagnetic fields, with the conclusion that “phone provider, as a surrogate for mobile phone use, could have resulted in considerable misclassification in exposure assessment.” Samet et all write that this was “a study considered by the IARC Working Group” but fail to report the conclusion by the Working Group. Samet et all do not mention the analytic studies we published in 2013, but they do reference an update of the Danish cohort study and Benson et al7—the latter also published in 2013. We have discussed elsewhere the increasing incidence of brain tumors in several countries including Denmark.
W
Copyright © 2014 by Lippincott Williams & Wilkins ISSN: 1044-3983/14/2504-0617 DOI: 10.1097/EDE.0000000000000115
There was a sharp increase in the incidence of brain tumors during 2003–2012 (41% in men and 46% in women). This casts doubt on the findings of both Deltour et al8 on glioma incidence in the Nordic countries during 1997–2008 and the recent report on the Danish cohort study on mobile phone users.6 In summary, we disagree with the way Samet et al1 have chosen to present evidence regarding mobile phones and cancer. We do, however, agree with the authors’ advice on “keeping people well-informed.” In considering the most up-to-date publications, we find increasing evidence of an association between the use of mobile or cordless phones and glioma and acoustic neuroma. Lennart Hardell Michael Carlberg Department of Oncology University Hospital Örebro, Sweden [email protected]
Fredrik Söderqvist Centre for Clinical Research Uppsala University Central Hospital of Västerås Västerås, Sweden
Kjell Hansson Mild Department of Radiation Physics Umeå University Umeå, Sweden
REFERENCES 1. Samet JM, Straif K, Schüz J, Saracci R. Commentary: mobile phones and cancer: next steps after the 2011 IARC review. Epidemiology. 2014;25:23–27. 2. Carlberg M, Söderqvist F, Hansson Mild K, Hardell L. Meningioma patients diagnosed 2007– 2009 and the association with use of mobile and cordless phones. Environ Health. 2013;12:60. 3. Hardell L, Carlberg M, Söderqvist F, Hansson Mild K. Pooled analysis of case-control studies on acoustic neuroma diagnosed 1997-2003 and 2007-2009 and use of mobile and cordless phones. Int J Oncol. 2013;43:1036–1044. 4. Hardell L, Carlberg M, Söderqvist F, Mild KH. Case-control study of the association between malignant brain tumours diagnosed between 2007 and 2009 and mobile and cordless phone use. Int J Oncol. 2013;43:1833–1845. 5. Hardell L, Carlberg M, Hansson Mild K. Re-analysis of risk for glioma in relation to mobile telephone use: comparison with the results of the Interphone international case-control study. Int J Epidemiol. 2011;40:1126–1128.
www.epidem.com | 617
Letters
TABLE. Associations of Salt Habits with Cancer Deaths in 17,733 Men and Women ≥16 Years of Age Basic Modela RR (95% CI) Adding salt to prepared meals Never 1.00 Occasionally 1.12 (0.99–1.27) Always 1.30 (1.04–1.62)
Basic Model + Smokingb RR (95% CI)
Basic Model + BMIc RR (95% CI)
Basic Model + Smoking + BMId RR (95% CI)
1.00 1.07 (0.95–1.21) 1.16 (0.93–1.45)
1.00 1.14 (1.00–1.28) 1.31 (1.05–1.63)
1.00 1.09 (0.96–1.23) 1.17 (0.94–1.47)
a
Adjusted for age, sex, and study wave. Additionally adjusted for smoking (never, former, and number of cigarettes). c Additionally adjusted for BMI. d Adjusted for all variables. b
for smoking substantially weakened this association, while adjustment for BMI had virtually no impact. In this general population sample from Switzerland, there was a doseresponse association between adding salt to a prepared meal and the risk of death from cancer. To some extent, this association was confounded by smoking. People who smoke may have a higher taste threshold than those who do not.2 Smokers may also differ in their health behavior patterns, including less attention to a healthy diet.6 Both salt sensitivity and eating patterns could also vary between normal weight and overweight people,3 although BMI did not appear to confound the salt-mortality association in our data. Our analysis was limited by the fact that salt habits and smoking were self-reported and assessed only once, at baseline. In addition, cancer-specific analyses were not possible due to relatively small number of cancer deaths.
REFERENCES 1. D’Elia L, Rossi G, Ippolito R, Cappuccio FP, Strazzullo P. Habitual salt intake and risk of gastric cancer: a meta-analysis of prospective studies. Clin Nutr. 2012;31:489–498. 2. Pavlos P, Vasilios N, Antonia A, Dimitrios K, Georgios K, Georgios A. Evaluation of young smokers and non-smokers with electrogustometry and contact endoscopy. BMC Ear Nose Throat Disord. 2009;9:9. 3. Pepino MY, Mennella JA. Cigarette smoking and obesity are associated with decreased fat perception in women. Obesity (Silver Spring). 2014;22:1050–1055. 4. Bopp M, Braun J, Faeh D, Gutzwiller F; Swiss National Cohort Study Group. Establishing a follow-up of the Swiss MONICA participants (1984-1993): record linkage with census and mortality data. BMC Public Health. 2010;10:562. 5. Bopp M, Braun J, Gutzwiller F, Faeh D; Swiss National Cohort Study Group. Health risk or resource? Gradual and independent association between self-rated health and mortality persists over 30 years. PLoS One. 2012;7:e30795. 6. Moreno-Gómez C, Romaguera-Bosch D, Tauler-Riera P, et al. Clustering of lifestyle factors in Spanish university students: the relationship between smoking, alcohol consumption, physical activity and diet quality. Public Health Nutr. 2012;15:2131–2139.
ACKNOWLEDGMENTS We thank Dr. Kelly Turner for proof reading. We thank the Swiss Federal Statistical Office for providing mortality and census data. David Faeh Sabine Rohrmann Milo Puhan Julia Braun Institute of Social and Preventive Medicine (ISPM) University of Zurich Zurich, Switzerland [email protected] 616 | www.epidem.com
Mobile Phones and Cancer Next Steps
To the Editor: amet and colleagues1 present the state of knowledge on mobile phones and cancer 2 years after the International
S
Copyright © 2014 by Lippincott Williams & Wilkins ISSN: 1044-3983/14/2504-0616 DOI: 10.1097/EDE.0000000000000118
Agency for Research on Cancer evaluation of radiofrequency radiation,2 which recommended a coordinated, strategic plan of epidemiologic research, experimental studies, and risk communication and management. Samet and colleagues1 describe results of recent epidemiologic studies, including analysis of data from 5 INTERPHONE countries using estimates of cumulative energy at tumor location.3 They report the increased glioma risk among heaviest users but omit important findings: a dose-response for glioma among long-term users and, in case-only analyses minimizing recall bias by ignoring reported amount and laterality of use, an increased odds ratio (OR) among longterm users in the most exposed part of the brain.3 They also do not mention a similar OR in case-specular analyses of data from 7 other INTERPHONE countries.4 Recommendations stemming from previous case-control studies include the following: (1) further development of radiofrequency radiation exposure modeling, (2) bias modeling, and (3) parallel reanalysis of the INTERPHONE and Hardell studies. We fully support such recommendations. Despite limitations of the case-control design—which must be addressed—this design is the most powerful for investigating potential associations between radiofrequency radiation and brain tumors. Prospective studies based on operator records are also recommended; although immune to recall bias, they are limited by statistical power (INTERPHONE captured a population of 50 million, hardly achievable in a cohort study), exposure assessment, and selection bias. Time-trend analyses are important for population surveillance but have limited power to detect risks of tumors arising only in the most exposed part of the brain, years after substantial exposure.2 Samet and colleagues1 also note the importance of developing and implementing a strategic research agenda and keeping the public well informed. The newly European Union–funded GERoNiMO project (geronimo.crealradiation.com) builds upon existing European resources (including large-scale © 2014 Lippincott Williams & Wilkins
Epidemiology • Volume 25, Number 4, July 2014 Letters
cohort and case-control studies) to: (1) better understand health effects (and mechanisms) potentially associated with electromagnetic fields (EMF), including brain tumors, neurodegenerative, behavioral, and reproductive outcomes; (2) better characterize EMF exposure in the general population; (3) improve integration of EMF and health research into health risk assessment; and (4) underpin risk management policies. GERoNiMO focuses on radiofrequency radiation (from mobile phones and newer communication technologies) and increasingly ubiquitous intermediate frequency fields—alone and in combination with other environmental exposures. We anticipate that GERoNiMO will improve the integration, coherence, and coordination of EMF and health research, leading to improved evidence-based risk estimation, management, and communication. Chelsea Eastman Langer James Grellier Michelle C. Turner Elisabeth Cardis Radiation Programme Centre for Research in Environmental Epidemiology (CREAL) Barcelona, Spain Universitat Pompeu Fabra (UPF) Barcelona, Spain Ciber Epidemiología y Salud Pública (CIBERESP) Madrid, Spain [email protected]
REFERENCES 1. Samet JM, Straif K, Schüz J, Saracci R. Commentary: Mobile Phones and Cancer: Next Steps After the 2011 IARC Review. Epidemiology. 2014;25:23–27. 2. Baan R, Grosse Y, Lauby-Secretan B, et al; WHO International Agency for Research on Cancer Monograph Working Group. Carcinogenicity of radiofrequency electromagnetic fields. Lancet Oncol. 2011;12: 624–626. 3. Cardis E, Armstrong BK, Bowman JD, et al. Risk of brain tumours in relation to estimated RF dose from mobile phones: results from five Interphone countries. Occup Environ Med. 2011;68:631–640. 4. Larjavaara S, Schüz J, Swerdlow A, et al. Location of gliomas in relation to mobile telephone use: a case-case and case-specular analysis. Am J Epidemiol. 2011;174:2–11.
© 2014 Lippincott Williams & Wilkins
Mobile Phones and Cancer Next Steps To the Editors: e welcome the commentary by Samet et al1 and their recommendation for reanalysis of the main case-control studies on radiofrequency electromagnetic fields (the basis of all wireless technology). This reanalysis is something we have also suggested. The authors discuss pros and cons for the IARC classification of radiofrequency electromagnetic fields as “possibly carcinogenic to humans” (group 2B). However, several more recently published articles are either misinterpreted in or omitted from their presentation— for instance, 3 articles published by our research group on meningioma,2 acoustic neuroma,3 and malignant brain tumors.4 Our study and the INTERPHONE study differ in their recruitment of cases and controls, participation rates, and assessment of exposure, but restricting to the same age groups and omitting the use of cordless phones (as in INTERPHONE) gives similar results.5 The Danish cohort study6 was included in the IARC evaluation of radiofrequency electromagnetic fields, with the conclusion that “phone provider, as a surrogate for mobile phone use, could have resulted in considerable misclassification in exposure assessment.” Samet et all write that this was “a study considered by the IARC Working Group” but fail to report the conclusion by the Working Group. Samet et all do not mention the analytic studies we published in 2013, but they do reference an update of the Danish cohort study and Benson et al7—the latter also published in 2013. We have discussed elsewhere the increasing incidence of brain tumors in several countries including Denmark.
W
Copyright © 2014 by Lippincott Williams & Wilkins ISSN: 1044-3983/14/2504-0617 DOI: 10.1097/EDE.0000000000000115
There was a sharp increase in the incidence of brain tumors during 2003–2012 (41% in men and 46% in women). This casts doubt on the findings of both Deltour et al8 on glioma incidence in the Nordic countries during 1997–2008 and the recent report on the Danish cohort study on mobile phone users.6 In summary, we disagree with the way Samet et al1 have chosen to present evidence regarding mobile phones and cancer. We do, however, agree with the authors’ advice on “keeping people well-informed.” In considering the most up-to-date publications, we find increasing evidence of an association between the use of mobile or cordless phones and glioma and acoustic neuroma. Lennart Hardell Michael Carlberg Department of Oncology University Hospital Örebro, Sweden [email protected]
Fredrik Söderqvist Centre for Clinical Research Uppsala University Central Hospital of Västerås Västerås, Sweden
Kjell Hansson Mild Department of Radiation Physics Umeå University Umeå, Sweden
REFERENCES 1. Samet JM, Straif K, Schüz J, Saracci R. Commentary: mobile phones and cancer: next steps after the 2011 IARC review. Epidemiology. 2014;25:23–27. 2. Carlberg M, Söderqvist F, Hansson Mild K, Hardell L. Meningioma patients diagnosed 2007– 2009 and the association with use of mobile and cordless phones. Environ Health. 2013;12:60. 3. Hardell L, Carlberg M, Söderqvist F, Hansson Mild K. Pooled analysis of case-control studies on acoustic neuroma diagnosed 1997-2003 and 2007-2009 and use of mobile and cordless phones. Int J Oncol. 2013;43:1036–1044. 4. Hardell L, Carlberg M, Söderqvist F, Mild KH. Case-control study of the association between malignant brain tumours diagnosed between 2007 and 2009 and mobile and cordless phone use. Int J Oncol. 2013;43:1833–1845. 5. Hardell L, Carlberg M, Hansson Mild K. Re-analysis of risk for glioma in relation to mobile telephone use: comparison with the results of the Interphone international case-control study. Int J Epidemiol. 2011;40:1126–1128.
www.epidem.com | 617
