James J. Weinkam

Publication Decisions Revisited: The Effect of the Outcome of Statistical Tests on the Decision to Publish and Vice Versa

Abstract This article presents evidence that published results of scientific investigations are not a representative sample of results of all scientific studies. Research studies from 11 major journals demonstrate the existence of biases that favor studies that observe effects that, on statistical evaluation, have a low probability of erroneously rejecting the so-called null hypothesis (H 0). This practice makes the probability of erroneously rejecting H 0 different for the reader than for the investigator. It introduces two biases in the interpretation of the scientific literature: one due to multiple repetition of studies with false hypothesis, and one due to failure to publish smaller and less significant outcomes of tests of a true hypotheses. These practices distort the results of literature surveys and of meta-analyses. These results also indicate that practice leading to publication bias have not changed over a period of 30 years.

The confounding of occupation and smoking and its consequences.

A strong pattern in smoking behavior can be demonstrated, in which smoking is much more prevalent among those occupational groups (and social strata) that are also more exposed to hazards in the workplace and much less prevalent among those groups less exposed to such hazards. As a consequence, comparing individuals with greater to those with lesser exposure to tobacco also compares groups that differ with respect to occupational exposure to dust, fumes and toxic substances and with respect to occupationally related lifestyle factors. Analyses of the U.S. National Health Interview Survey show that smoking and occupation are substantially confounded among individuals differing by (1) amount of smoking; (2) smoking cessation; (3) types of cigarettes smoked; (4) age of starting to smoke; and (5) exposure to more or less environmental tobacco smoke at home. This confounding between types of work and proximity to tobacco smoke may have masked relationships between type of employment and disease. But it is difficult to disentangle the effects of occupation and of smoking from each other without well planned further studies because (1) of the difficulty of estimating occupational effects and simultaneously adjusting for healthy worker effects, (2) satisfactory techniques for estimating relative effects of intertwined variables make demands on the quality and quantity of data that are not met by presently available data, and (3) there may be deeply rooted social and psychological attitudes toward effects of work versus effects of lifestyles that tend to bias investigative work.

Analysis of the relationship between smokeless tobacco and cancer based on data from the National Mortality Followback Survey

This study investigates the potential link between the use of smokeless tobacco and oral cancer and cancer of digestive organs. The combined data of the National Mortality Followback Survey (NMFS), a probability sample of the U.S. deaths, and the coincident National Health Interview Survey (NHIS), a probability sample of the living, non-institutionalized U.S. population, are used to compute risk estimates for cancer, oral cancer, and cancer of the digestive organs associated with use of smokeless tobacco based on a cross sectional study design, simultaneously controlled for potential confounding from active smoking, alcohol consumption, and occupational exposure. Use of smokeless tobacco (either as snuff or chewing tobacco) does not increase the risk of oral cancer or cancer of the digestive organs. Alcohol emerges as a major risk factor for oral cancer with a strong dose-response relationship between the amount of drinking and risk. The same is true to a lesser extent for cancer of the digestive organs. Smoking is associated with increased risk of oral cancer but not of cancer of the digestive organs. Blue collar, technical, and service workers have significantly increased risk of cancer of the digestive organs relative to professional, managerial, and clerical workers, but not of oral cancer. Differences between findings based on the NMFS/NHIS and those obtained from other data very likely are due to inadequate control for confounding. Other reasons for differences between the NMFS/NHIS data and other studies are discussed.

Automatic variation of field size and dose rate in rotation therapy.

Abstract A technique is presented for changing the field size and dose rate as a function of gantry angle independently or simultaneously during rotation therapy. Two computational methods for calculating the dose distribution using the above technique are described. A comparison of the effectiveness of this new technique relative to conventional approaches is discussed.

Automation of Radiation Treatment Planning. V—Calculation and Visualisation of the Total Treatment Volume

The method for calculating per cent depth doses for all points in the major plane of a 60Co beam has been extended to all points in the treatment volume. An outline for rapid calculation of volumes of co- or multiplanar treatment plans is presented and an application of the system demonstrated.

Bias in the attribution of lung cancer as cause of death and its possible consequences for calculating smoking-related risks.

Most published calculations of mortality risk, especially those for lung cancer associated with smoking, are based almost exclusively on the underlying cause as recorded on death certificates. Such risk calculations implicitly assume that the conditional probability of recording lung cancer as the underlying cause of death, given that it really is the underlying cause, is the same for all exposure groups. If these probabilities are not equal for all exposure groups, we call the resulting bias a cause of death attribution bias. We analyzed the 1986 National Mortality Followback Survey, a sample of 18,733 U.S. death certificates, and the 1954–1962 Dorn study, a follow-up study of approximately 250,000 holders of U.S. Veterans Life Insurance. Both data sets include information on the smoking habits of decedents and on the underlying and contributing causes of their deaths. We found that lung cancer as an underlying cause is recorded with a much smaller relative frequency if the decedent is known to be a never-smoker and with a much larger relative frequency when the decedent is known to be a smoker. On the other hand, lung cancer as a contributing cause is recorded with a much larger frequency if the decedent is known to be a never-smoker and with a much smaller frequency when the decedent is known to be a smoker. The reverse is true for cancers other than of the lung. There is no similar pattern related to smoking for other causes of death (specifically for myocardial infarction, other chronic ischemic heart disease, diabetes, or cerebrovascular disease). This pattern provides evidence of a possible bias because knowledge of a decedents smoking status appears to influence the designation of lung cancer or some other cancer as the underlying cause or a contributing cause of death. This bias is especially strong when the choice of possible underlying causes of death is limited to one of a number of cancers. Insofar as calculations of lung cancer risk utilize exclusively recorded underlying causes, the observed attribution bias must result in an overestimate of the lung cancer mortality rate for smokers. (Epidemiology 1992;3:11–16)

Dynamic display of radiotherapy plans using computer-produced films.

Computer-produced animated films may have practical implications for radiation therapy planning, especially when coupled with cinematic technology. Such films may help the radiotherapist understand relationships between dose distributions and organ locations in the three-dimensional target volume. Techniques of producing films for treatment planning are described, and an experimental film devised for a mantle field treatment is illustrated.

Sharing scientific data

The willingness of one scientist to share data with another scientist continues to be influenced by a number of enconomic, social, psychological and political factors.

The sick person effect.

Very often criteria by which subjects are selected for epidemiological studies are associated in some manner with their health. The Healthy Worker Effect (HWE) or Healthy Person Effect (HPE) is well known. Little has been said about the converse case in which selection is associated with decreased health status, the Sick Person Effect (SPE). The SPE may introduce a bias for some cohort, most clinical follow-up, and some case-control studies when risks are standardized against an inappropriate referent. We demonstrate the existence of the SPE in two studies. Study 1 compares the incidence of a number of different diseases among individuals who were selected as children for medical treatment with that among their siblings. Study 2 computes the Standardized Morbidity Ratios (SmRs) for various acute and chronic diseases for individuals who have reported particular chronic symptoms. The SPE is clearly apparent for all instances where the general population is taken as the referent. The HPE and SPE may present serious problems for the validity of conclusions with respect to risk levels.

Automation of radiation treatment planning. III. A simplified system of digitising isodoses and direct print-out of dose distribution

A system of automated treatment planning is described which enables the radiologist to obtain a direct print-out to scale of dose distribution. This system requires a new and simple method of digitising isodose curves which is also given.