Scientific Evidence Portal
Why Most Published Research Findings Are False | John P. A. Ioannidis
Article Published: 2005
Type: Articles and Dissertations
Published By: PLoS Medicine, August 2005, Volume 2, Issue 8
An interesting (and technical) analysis of multifactorial epidemiology – the numerological "science" of the 21st century – is provided in this work. Particularly, Ioannidis points out that the accuracy and reliability of epidemiological studies decreases enormously with the decreasing size of the risk that is supposedly “measured” (emphasis added).
“The smaller the effect sizes in a scientific field, the less likely the research findings are to be true. Power is also related to the effect size. Thus research findings are more likely true in scientific fields with large effects, such as the impact of [active] smoking on cancer or cardiovascular disease (relative risks 3–20), than in scientific fields where postulated effects are small, such as genetic risk factors for multigenetic diseases (relative risks 1.1–1.5).
Modern epidemiology is increasingly obliged to target smaller effect sizes. Consequently, the proportion of true research findings is expected to decrease. In the same line of thinking, if the true effect sizes are very small in a scientific field, this field is likely to be plagued by almost ubiquitous false positive claims.”
The Reader should also be reminded that the typically touted risk estimate of lung cancer from exposure to passive smoking is around 1.2.
In addition to what Ioannidis highlights, it is important to remember that the basic data collection of the studies on passive smoking is based on vague memory recalls of unverifiable exposures usually dating back may decades, often not even reported by the subjects themselves, but by the heirs of the deceased.
Add to all that political, financial and ideological motivations, and the inevitable conclusion is that the epidemiology on passive smoking is completely worthless.