Reductions in death rates from four major cancers in the United States in recent years were generally confined to better-educated individuals, and epidemiological studies on cancer and other diseases are vulnerable to false-positive findings, according to two papers published online July 8 in the Journal of the National Cancer Institute.

In the first study, Tracy Kinsey, of Emory University in Atlanta, and colleagues analyzed data from death certificates for 1993 through 2001 for lung, breast, prostate and colorectal cancer among non-Hispanic white and black men and women aged 25 to 64. Death rates for all the cancers fell significantly in nearly all of these groups for individuals with at least 16 years of education, the researchers report. However, in those with less than 12 years of education, death rates for these cancers generally stayed stable or rose during this period.

In the other paper, which is a commentary from Paolo Boffetta, M.D., Ph.D., of the International Agency for Research on Cancer in Lyon, France, and colleagues, the authors describe likely false-positive results that weren't later confirmed, such as a 1993 case-control study linking the pollutant DDE and breast cancer risk, or studies from 1980 to 1998 on occupational exposure to acrylonitrile and lung cancer that found a steadily decreasing association. False-positive results may arise due to chance, recall bias, selection bias, confounding and publication bias, the authors write.

"A careful analysis of factors enhancing the likelihood of false-positive reporting should be part of the training of epidemiologists, and these issues should be addressed in the 'Discussion' section of every epidemiological paper. In general, epidemiologists should recognize the reporting of false-positive results as a major challenge to the scientific credibility of their discipline and institutionalize a greater level of epistemological modesty in this regard," Boffetta and colleagues conclude.

Abstract - Kinsey
Full Text
Abstract - Boffetta
Full Text

Prepared jointly by the editors of RN and HealthDay's Physicians' Briefing (www.physiciansbriefing.com).